[Boost-commit] svn:boost r80338 - in trunk: boost/context/detail libs/context/build libs/context/doc libs/context/example libs/context/performance libs/context/src libs/context/src/asm libs/context/test

Subject: [Boost-commit] svn:boost r80338 - in trunk: boost/context/detail libs/context/build libs/context/doc libs/context/example libs/context/performance libs/context/src libs/context/src/asm libs/context/test
From: oliver.kowalke_at_[hidden]
Date: 2012-08-31 15:50:10

Author: olli
Date: 2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
New Revision: 80338
URL: http://svn.boost.org/trac/boost/changeset/80338

Log:
context: new layout for fcontext_t
 - fcontext_t takes pointer to stack (lower addresses) and stack size
 - make_fcontext() computes start address of stack pointer depending on
   architecture (growing upwards, downwards)
 - make_fcontext() preserves frame pointer on intel
 - stack alignment corrected on intel
 - BOOST_USE_UCONTEXT for performance measurements added

Removed:
   trunk/libs/context/doc/config.qbk
Text files modified: 
   trunk/boost/context/detail/fcontext_arm.hpp                 |     4                                         
   trunk/boost/context/detail/fcontext_i386.hpp                |     4                                         
   trunk/boost/context/detail/fcontext_i386_win.hpp            |     6                                         
   trunk/boost/context/detail/fcontext_mips.hpp                |     4                                         
   trunk/boost/context/detail/fcontext_ppc.hpp                 |     4                                         
   trunk/boost/context/detail/fcontext_x86_64.hpp              |     4                                         
   trunk/boost/context/detail/fcontext_x86_64_win.hpp          |     6                                         
   trunk/libs/context/build/Jamfile.v2                         |   241 +++++++++++++++++++++++++++++---------- 
   trunk/libs/context/doc/fcontext.qbk                         |     7                                         
   trunk/libs/context/doc/performance.qbk                      |     3                                         
   trunk/libs/context/doc/requirements.qbk                     |     8                                         
   trunk/libs/context/doc/stack.qbk                            |    12 +                                       
   trunk/libs/context/example/exit.cpp                         |     4                                         
   trunk/libs/context/example/jump.cpp                         |     4                                         
   trunk/libs/context/example/transfer.cpp                     |     2                                         
   trunk/libs/context/performance/performance.cpp              |   122 +++++++++----------                     
   trunk/libs/context/src/asm/fcontext_arm_aapcs_elf_gas.S     |     4                                         
   trunk/libs/context/src/asm/fcontext_i386_ms_pe_masm.asm     |    61 +++++----                               
   trunk/libs/context/src/asm/fcontext_i386_sysv_elf_gas.S     |    52 ++++---                                 
   trunk/libs/context/src/asm/fcontext_i386_sysv_macho_gas.S   |    45 ++++---                                 
   trunk/libs/context/src/asm/fcontext_mips32_o32_elf_gas.S    |     4                                         
   trunk/libs/context/src/asm/fcontext_ppc32_sysv_elf_gas.S    |     4                                         
   trunk/libs/context/src/asm/fcontext_ppc64_sysv_elf_gas.S    |     4                                         
   trunk/libs/context/src/asm/fcontext_x86_64_ms_pe_masm.asm   |    56 ++++----                                
   trunk/libs/context/src/asm/fcontext_x86_64_sysv_elf_gas.S   |    51 +++++---                                
   trunk/libs/context/src/asm/fcontext_x86_64_sysv_macho_gas.S |    51 +++++---                                
   trunk/libs/context/src/stack_allocator_posix.cpp            |    15 +-                                      
   trunk/libs/context/src/stack_allocator_windows.cpp          |    17 +-                                      
   trunk/libs/context/src/stack_utils_posix.cpp                |    48 +++++--                                 
   trunk/libs/context/src/stack_utils_windows.cpp              |    57 +++++---                                
   trunk/libs/context/test/test_context.cpp                    |    22 ++-                                     
   31 files changed, 573 insertions(+), 353 deletions(-)

Modified: trunk/boost/context/detail/fcontext_arm.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_arm.hpp	(original)
+++ trunk/boost/context/detail/fcontext_arm.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -27,11 +27,11 @@
 
 struct stack_t
 {
-    void    *   base;
+    void    *   sp;
     std::size_t size;
 
     stack_t() :
-        base( 0), size( 0)
+        sp( 0), size( 0)
     {}
 };
 

Modified: trunk/boost/context/detail/fcontext_i386.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_i386.hpp	(original)
+++ trunk/boost/context/detail/fcontext_i386.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -27,11 +27,11 @@
 
 struct stack_t
 {
-    void    *   base;
+    void    *   sp;
     std::size_t size;
 
     stack_t() :
-        base( 0), size( 0)
+        sp( 0), size( 0)
     {}
 };
 

Modified: trunk/boost/context/detail/fcontext_i386_win.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_i386_win.hpp	(original)
+++ trunk/boost/context/detail/fcontext_i386_win.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -36,12 +36,12 @@
 
 struct stack_t
 {
-    void    *   base;
-    void    *   limit;
+    void    *   sp;
     std::size_t size;
+    void    *   limit;
 
     stack_t() :
-        base( 0), limit( 0), size( 0)
+        sp( 0), size( 0), limit( 0)
     {}
 };
 

Modified: trunk/boost/context/detail/fcontext_mips.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_mips.hpp	(original)
+++ trunk/boost/context/detail/fcontext_mips.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -29,11 +29,11 @@
 
 struct stack_t
 {
-    void    *   base;
+    void    *   sp;
     std::size_t size;
 
     stack_t() :
-        base( 0), size( 0)
+        sp( 0), size( 0)
     {}
 };
 

Modified: trunk/boost/context/detail/fcontext_ppc.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_ppc.hpp	(original)
+++ trunk/boost/context/detail/fcontext_ppc.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -27,11 +27,11 @@
 
 struct stack_t
 {
-    void    *   base;
+    void    *   sp;
     std::size_t size;
 
     stack_t() :
-        base( 0), size( 0)
+        sp( 0), size( 0)
     {}
 };
 

Modified: trunk/boost/context/detail/fcontext_x86_64.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_x86_64.hpp	(original)
+++ trunk/boost/context/detail/fcontext_x86_64.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -27,11 +27,11 @@
 
 struct stack_t
 {
-    void    *   base;
+    void    *   sp;
     std::size_t size;
 
     stack_t() :
-        base( 0), size( 0)
+        sp( 0), size( 0)
     {}
 };
 

Modified: trunk/boost/context/detail/fcontext_x86_64_win.hpp
==============================================================================
--- trunk/boost/context/detail/fcontext_x86_64_win.hpp	(original)
+++ trunk/boost/context/detail/fcontext_x86_64_win.hpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -36,12 +36,12 @@
 
 struct stack_t
 {
-    void    *   base;
-    void    *   limit;
+    void    *   sp;
     std::size_t size;
+    void    *   limit;
 
     stack_t() :
-        base( 0), limit( 0), size( 0)
+        sp( 0), size( 0), limit( 0)
     {}
 };
 

Modified: trunk/libs/context/build/Jamfile.v2
==============================================================================
--- trunk/libs/context/build/Jamfile.v2	(original)
+++ trunk/libs/context/build/Jamfile.v2	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -23,255 +23,374 @@
       <link>shared:<define>BOOST_CONTEXT_DYN_LINK=1
     ;
 
+local rule default_binary_format ( )
+{
+    local tmp = elf ;
+    if [ os.name ] = "MACOSX" { tmp = mach-o ; }
+    if [ os.name ] = "NT" { tmp = pe ; }
+    return $(tmp) ;
+}
+
+feature.feature binary-format
+   : elf
+     mach-o
+     pe
+   : propagated
+   ;
+feature.set-default binary-format : [ default_binary_format ] ;
+
+
+local rule default_abi ( )
+{
+    local tmp = sysv ;
+    if [ os.name ] = "NT" { tmp = ms ; }
+    else if [ os.platform ] = "ARM" { tmp = aapcs ; }
+    else if [ os.platform ] = "MIPS" { tmp = o32 ; }
+    return $(tmp) ;
+}
+
+feature.feature abi
+   : aapcs
+     eabi
+     ms
+     n32
+     n64
+     o32
+     o64
+     sysv
+   : propagated
+   ;
+feature.set-default abi : [ default_abi ] ;
+
 
 actions gas
 {
-	as -o "$(<)" "$(>)"
+    as -o "$(<)" "$(>)"
 }
 
 actions masm
 {
-	ml /c /Fo"$(<)" "$(>)"
+    ml /c /Fo"$(<)" "$(>)"
 }
 
 actions masm64
 {
-	ml64 /c /Fo"$(<)" "$(>)"
+    ml64 /c /Fo"$(<)" "$(>)"
 }
 
 
 rule configure ( properties * )
 {
-	local result  ;
+    local result  ;
+
+#   if ( ! ( <toolset>gcc in $(properties)
+#           || <toolset>intel in $(properties)
+#           || <toolset>msvc in $(properties) ) )
+#   {
+#       result = <build>no ;
+#       ECHO "toolset not supported" ;
+#   }
 
-	return $(result) ;
+    return $(result) ;
 }
 
 # ARM
 alias asm_context_sources
    : asm/fcontext_arm_aapcs_elf_gas.S
-   : <architecture>arm
-	 <toolset>gcc
+   : <abi>aapcs
+     <architecture>arm
+     <binary-format>elf
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_arm_aapcs_elf_gas.S
-   : <architecture>arm
-	 <toolset>qcc
+   : <abi>aapcs
+     <architecture>arm
+     <binary-format>elf
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_arm_aapcs_elf_gas.o : asm/fcontext_arm_aapcs_elf_gas.S : @gas ]
-   : <architecture>arm
+   : <abi>aapcs
+     <architecture>arm
+     <binary-format>elf
    ;
 
 # MIPS 32bit
 alias asm_context_sources
    : asm/fcontext_mips32_o32_elf_gas.S
-   : <architecture>mips1
-	 <toolset>gcc
+   : <abi>o32
+     <architecture>mips1
+     <binary-format>elf
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_mips32_o32_elf_gas.S
-   : <architecture>mips1
-	 <toolset>qcc
+   : <abi>o32
+     <architecture>mips1
+     <binary-format>elf
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_mips32_o32_elf_gas.o : asm/fcontext_mips32_o32_elf_gas.S : @gas ]
-   : <architecture>mips1
+   : <abi>o32
+     <architecture>mips1
+     <binary-format>elf
    ;
 
 # POWERPC 32bit
 alias asm_context_sources
    : asm/fcontext_ppc32_sysv_elf_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>power
-	 <toolset>gcc
+     <binary-format>elf
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_ppc32_sysv_elf_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>power
-	 <toolset>qcc
+     <binary-format>elf
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_ppc32_sysv_elf_gas.o : asm/fcontext_ppc32_sysv_elf_gas.S : @gas ]
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>power
+     <binary-format>elf
    ;
 
 # POWERPC 64bit
 alias asm_context_sources
    : asm/fcontext_ppc64_sysv_elf_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>power
-	 <toolset>gcc
+     <binary-format>elf
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_ppc64_sysv_elf_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>power
-	 <toolset>qcc
+     <binary-format>elf
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_ppc64_sysv_elf_gas.o : asm/fcontext_ppc64_sysv_elf_gas.S : @gas ]
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>power
+     <binary-format>elf
    ;
 
 # I386
 alias asm_context_sources
    : asm/fcontext_i386_sysv_elf_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
-	 <toolset>gcc
+     <binary-format>elf
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_i386_sysv_elf_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
-	 <toolset>qcc
+     <binary-format>elf
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_i386_sysv_elf_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
-	 <toolset>intel
+     <binary-format>elf
+     <toolset>intel
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_i386_sysv_elf_gas.o : asm/fcontext_i386_sysv_elf_gas.S : @gas ]
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
+     <architecture>x86
+     <binary-format>elf
+   ;
+
+alias asm_context_sources
+   : asm/fcontext_i386_sysv_macho_gas.S
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
+     <binary-format>mach-o
+     <target-os>darwin
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_i386_sysv_macho_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
+     <binary-format>mach-o
      <target-os>darwin
-	 <toolset>gcc
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_i386_sysv_macho_gas.S
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
+     <binary-format>mach-o
      <target-os>darwin
-	 <toolset>intel
+     <toolset>intel
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_i386_sysv_macho_gas.o : asm/fcontext_i386_sysv_macho_gas.S : @gas ]
-   : <address-model>32
+   : <abi>sysv
+     <address-model>32
      <architecture>x86
+     <binary-format>mach-o
      <target-os>darwin
    ;
 
 alias asm_context_sources
    : asm/fcontext_i386_ms_pe_masm.asm
-   : <address-model>32
+   : <abi>ms
+     <address-model>32
      <architecture>x86
+     <binary-format>pe
      <target-os>windows
-	 <toolset>intel
+     <toolset>intel
    ;
 
 alias asm_context_sources
    : asm/fcontext_i386_ms_pe_masm.asm
-   : <address-model>32
+   : <abi>ms
+     <address-model>32
      <architecture>x86
+     <binary-format>pe
      <target-os>windows
-	 <toolset>msvc
+     <toolset>msvc
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_i386_ms_pe_masm.o : asm/fcontext_i386_ms_pe_masm.asm : @masm ]
-   : <address-model>32
+   : <abi>ms
+     <address-model>32
      <architecture>x86
+     <binary-format>pe
      <target-os>windows
    ;
 
-
 # X86_64
 alias asm_context_sources
    : asm/fcontext_x86_64_sysv_elf_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
-	 <toolset>gcc
+     <binary-format>elf
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_x86_64_sysv_elf_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
-	 <toolset>qcc
+     <binary-format>elf
+     <toolset>qcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_x86_64_sysv_elf_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
-	 <toolset>intel
+     <binary-format>elf
+     <toolset>intel
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_x86_64_sysv_elf_gas.o : asm/fcontext_x86_64_sysv_elf_gas.S : @gas ]
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
+     <binary-format>elf
    ;
 
-
 alias asm_context_sources
    : asm/fcontext_x86_64_sysv_macho_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
+     <binary-format>mach-o
      <target-os>darwin
-	 <toolset>gcc
+     <toolset>gcc
    ;
 
 alias asm_context_sources
    : asm/fcontext_x86_64_sysv_macho_gas.S
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
+     <binary-format>mach-o
      <target-os>darwin
-	 <toolset>intel
+     <toolset>intel
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_x86_64_sysv_macho_gas.o : asm/fcontext_x86_64_sysv_macho_gas.S : @gas ]
-   : <address-model>64
+   : <abi>sysv
+     <address-model>64
      <architecture>x86
+     <binary-format>mach-o
      <target-os>darwin
    ;
 
 alias asm_context_sources
    : asm/fcontext_x86_64_ms_pe_masm.asm
-   : <address-model>64
+   : <abi>ms
+     <address-model>64
      <architecture>x86
+     <binary-format>pe
      <target-os>windows
-	 <toolset>intel
+     <toolset>intel
    ;
 
 alias asm_context_sources
    : asm/fcontext_x86_64_ms_pe_masm.asm
-   : <address-model>64
+   : <abi>ms
+     <address-model>64
      <architecture>x86
+     <binary-format>pe
      <target-os>windows
-	 <toolset>msvc
+     <toolset>msvc
    ;
 
 alias asm_context_sources
    : [ make asm/fcontext_x86_64_ms_pe_masm.o : asm/fcontext_x86_64_ms_pe_masm.asm : @masm64 ]
-   : <address-model>64
+   : <abi>ms
+     <address-model>64
      <architecture>x86
+     <binary-format>pe
      <target-os>windows
    ;
 

Deleted: trunk/libs/context/doc/config.qbk
==============================================================================
--- trunk/libs/context/doc/config.qbk	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
+++ (empty file)
@@ -1,60 +0,0 @@
-[/
-          Copyright Oliver Kowalke 2009.
- Distributed under the Boost Software License, Version 1.0.
-    (See accompanying file LICENSE_1_0.txt or copy at
-          http://www.boost.org/LICENSE_1_0.txt
-]
-
-[section:installtion How to build and install]
-
-__boost_context__ must be built for the particular compiler(s) and CPU architecture(s)s
-being targeted. __boost_context__ includes assembly code and, therefore, requires
-GNU AS for supported POSIX systems, and MASM for Windows systems.
-
-[note The architecture, instruction set, and address model are optional __boost_build__
-properties that must be given on the bjam command line, as shown in the table below.] 
-
-[table
-    [[][]]
-    [
-        [ARM, UNIX, aapcs, elf]
-        [bjam toolset = gcc architecture = arm]
-    ]
-    [
-        [MIPS (32bit), UNIX, o32, elf]
-        [bjam toolset = gcc architecture = mips1]
-    ]
-    [
-        [I386, UNIX, sysv, elf]
-        [bjam toolset = gcc architecture = x86 instruction-set = i686 address-model = 32]
-    ]
-    [
-        [I386, UNIX, sysv, elf]
-        [bjam toolset = intel architecture = x86 instruction-set = i686 address-model = 32]
-    ]
-    [
-        [I386, Windows, ms, pe]
-        [bjam toolset = msvc-9.0 architecture = x86 instruction-set = i686 address-model = 32]
-    ]
-    [
-        [PowerPc (32bit), UNIX, sysv, elf]
-        [bjam toolset = gcc architecture = power address-model = 32]
-    ]
-    [
-        [PowerPc (64bit), UNIX, sysv, elf]
-        [bjam toolset = gcc architecture = power address-model = 64]
-    ]
-    [
-        [X86_64, UNIX, sysv, elf]
-        [bjam toolset = gcc architecture = x86 instruction-set = yorksfield address-model = 64]
-    ]
-    [
-        [X86_64, UNIX, sysv, elf]
-        [bjam toolset = intel architecture = x86 instruction-set = yorksfield address-model = 64]
-    ]
-    [
-        [X86_64, Windows, ms, pe]
-        [bjam toolset = msvc-10.0 architecture = x86 instruction-set = yorksfield address-model = 64]
-    ]
-]
-[endsect]

Modified: trunk/libs/context/doc/fcontext.qbk
==============================================================================
--- trunk/libs/context/doc/fcontext.qbk	(original)
+++ trunk/libs/context/doc/fcontext.qbk	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -11,7 +11,8 @@
 space). Together with its related functions __jump_fcontext__ and
 __make_fcontext__ it provides a execution control transfer mechanism similar
 interface like
-[@http://www.kernel.org/doc/man-pages/online/pages/man2/getcontext.2.html ucontext_t].
+[@http://www.kernel.org/doc/man-pages/online/pages/man2/getcontext.2.html
+ucontext_t].
 __fcontext__ and its functions are located in __context_ns__ and the functions
 are declared as extern "C". 
 
@@ -40,8 +41,8 @@
             // context fc uses f() as context function
             make_fcontext( & fc, f);
 
-__fcontext__ requires a pointer to the top of the stack (__fc_base__) as well
-as the size of the stack.
+__fcontext__ requires a pointer (__fc_base__) as well as the size of the
+stack.
 
 Calling __jump_fcontext__ invokes the __context_fn__ in a newly created context
 complete with registers, flags, stack and instruction pointers.  When control

Modified: trunk/libs/context/doc/performance.qbk
==============================================================================
--- trunk/libs/context/doc/performance.qbk	(original)
+++ trunk/libs/context/doc/performance.qbk	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -14,6 +14,9 @@
 to a single CPU. The code was compiled using the build options,
 'variant = release cxxflags = -DBOOST_DISABLE_ASSERTS'.
 
+Applying `-DBOOST_USE_UCONTEXT` to cxxflags the performance of `ucontext` will
+be measured too.
+
 The numbers in the table are the number of cycles per iteration, based upon an
 average computed over 10 iterations.
 

Modified: trunk/libs/context/doc/requirements.qbk
==============================================================================
--- trunk/libs/context/doc/requirements.qbk	(original)
+++ trunk/libs/context/doc/requirements.qbk	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -12,7 +12,11 @@
 therefore, requires GNU AS for supported POSIX systems, and MASM for Windows
 systems.
 
-[important Please note that address-model=64 must be given to bjam command line
-on 64bit Windows (boost-build issue).]
+[important Please note that `address-model=64` must be given to bjam command line
+on 64bit Windows for 64bit build; otherwise 32bit code will be generated.]
+
+[important For cross-compiling the lib you must specify certain additional
+properties at bjam command line: `target-os`, `abi`, `binary-format`,
+`architecture` and `address-model`.]
 
 [endsect]

Modified: trunk/libs/context/doc/stack.qbk
==============================================================================
--- trunk/libs/context/doc/stack.qbk	(original)
+++ trunk/libs/context/doc/stack.qbk	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -50,9 +50,9 @@
 
 __boost_context__ provides a __stack_allocator__ `stack_allocator` which models
 the __stack_allocator_concept__ concept.
-It appends a __guard_page__ to protect against exceeding the stack. If the guard
-page is accessed (read or write operation) a segmentation fault/access violation
-is generated by the operating system.
+It creates a __guard_page__ at the end of the stack to protect against exceeding
+the stack. If the guard page is accessed (read or write operation) a
+segmentation fault/access violation is generated by the operating system.
 
 [endsect]
 
@@ -77,12 +77,14 @@
 [heading `std::size_t default_stacksize()`]
 [variablelist
 [[Returns:] [Returns a default stack size, which may be platform specific.
-The present implementation returns a value of 256 kB.]]
+If the stack is unbound then the present implementation returns the maximum of
+`256 kB` and `minimum_stacksize()`.]]
 ]
 
 [heading `std::size_t minimum_stacksize()`]
 [variablelist
-[[Returns:] [Returns the minimum size in bytes of stack defined by the environment.]]
+[[Returns:] [Returns the minimum size in bytes of stack defined by the
+environment plus a pagesize (guard page).]]
 [[Throws:] [Nothing.]]
 ]
 

Modified: trunk/libs/context/example/exit.cpp
==============================================================================
--- trunk/libs/context/example/exit.cpp	(original)
+++ trunk/libs/context/example/exit.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -37,11 +37,11 @@
         ctx::fcontext_t fcm;
         ctx::stack_allocator alloc;
 
-        fc1.fc_stack.base = alloc.allocate(ctx::minimum_stacksize());
+        fc1.fc_stack.sp = alloc.allocate(ctx::minimum_stacksize());
         fc1.fc_stack.size = ctx::minimum_stacksize();
         ctx::make_fcontext( & fc1, f1);
 
-        fc2.fc_stack.base = alloc.allocate(ctx::minimum_stacksize());
+        fc2.fc_stack.sp = alloc.allocate(ctx::minimum_stacksize());
         fc2.fc_stack.size = ctx::minimum_stacksize();
         ctx::make_fcontext( & fc2, f2);
 

Modified: trunk/libs/context/example/jump.cpp
==============================================================================
--- trunk/libs/context/example/jump.cpp	(original)
+++ trunk/libs/context/example/jump.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -37,11 +37,11 @@
 {
         ctx::stack_allocator alloc1, alloc2;
 
-        fc1.fc_stack.base = alloc1.allocate(ctx::minimum_stacksize());
+        fc1.fc_stack.sp = alloc1.allocate(ctx::minimum_stacksize());
         fc1.fc_stack.size = ctx::minimum_stacksize();
         ctx::make_fcontext( & fc1, f1);
 
-        fc2.fc_stack.base = alloc2.allocate(ctx::minimum_stacksize());
+        fc2.fc_stack.sp = alloc2.allocate(ctx::minimum_stacksize());
         fc2.fc_stack.size = ctx::minimum_stacksize();
         ctx::make_fcontext( & fc2, f2);
 

Modified: trunk/libs/context/example/transfer.cpp
==============================================================================
--- trunk/libs/context/example/transfer.cpp	(original)
+++ trunk/libs/context/example/transfer.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -32,7 +32,7 @@
 {
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate(ctx::minimum_stacksize());
+    fc1.fc_stack.sp = alloc.allocate(ctx::minimum_stacksize());
     fc1.fc_stack.size = ctx::minimum_stacksize();
     ctx::make_fcontext( & fc1, f1);
 

Modified: trunk/libs/context/performance/performance.cpp
==============================================================================
--- trunk/libs/context/performance/performance.cpp	(original)
+++ trunk/libs/context/performance/performance.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -19,7 +19,7 @@
 #include <boost/preprocessor/repetition/repeat_from_to.hpp>
 #include <boost/program_options.hpp>
 
-#ifndef BOOST_WINDOWS
+#ifdef BOOST_USE_UCONTEXT
 #include <ucontext.h>
 #endif
 
@@ -32,48 +32,51 @@
 
 namespace ctx = boost::ctx;
 
-bool preserve_fpu = false;
+bool pres_fpu = false;
 
-#define CALL_FUNCTION(z,n,unused) \
-    fn();
+#define CALL_FCONTEXT(z,n,unused) ctx::jump_fcontext( & fcm, & fc, 7, pres_fpu);
 
-#define CALL_UCONTEXT(z,n,unused) \
-    ::swapcontext( & ucm, & uc);
+#ifdef BOOST_USE_UCONTEXT
+# define CALL_UCONTEXT(z,n,unused) ::swapcontext( & ucm, & uc);
+#endif
+
+#define CALL_FUNCTION(z,n,unused) fn();
 
-#define CALL_FCONTEXT(z,n,unused) \
-    ctx::jump_fcontext( & fcm, & fc, 7, preserve_fpu);
 
-#ifndef BOOST_WINDOWS
+ctx::fcontext_t fc, fcm;
+
+#ifdef BOOST_USE_UCONTEXT
 ucontext_t uc, ucm;
 #endif
-ctx::fcontext_t fc, fcm;
 
-static void f3()
-{ }
 
-#ifndef BOOST_WINDOWS
+static void f1( intptr_t)
+{ while ( true) ctx::jump_fcontext( & fc, & fcm, 7, pres_fpu); }
+
+#ifdef BOOST_USE_UCONTEXT
 static void f2()
-{
-    while ( true)
-        ::swapcontext( & uc, & ucm);
-}
+{ while ( true) ::swapcontext( & uc, & ucm); }
 #endif
 
-static void f1( intptr_t)
-{
-    while ( true)
-        ctx::jump_fcontext( & fc, & fcm, 7, preserve_fpu);
-}
+static void f3()
+{}
+
 
 #ifdef BOOST_CONTEXT_CYCLE
-cycle_t test_function_cycle( cycle_t ov)
+cycle_t test_fcontext_cycle( cycle_t ov)
 {
-    boost::function< void() > fn( boost::bind( f3) );
+    ctx::stack_allocator alloc;
+    fc.fc_stack.sp = alloc.allocate(ctx::default_stacksize());
+    fc.fc_stack.size = ctx::default_stacksize();
+    ctx::make_fcontext( & fc, f1);
+
+    ctx::jump_fcontext( & fcm, & fc, 7, pres_fpu);
+
     // cache warum-up
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
 
     cycle_t start( cycles() );
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
     cycle_t total( cycles() - start);
 
     // we have two jumps and two measuremt-overheads
@@ -84,15 +87,13 @@
     return total;
 }
 
-#ifndef BOOST_WINDOWS
+# ifdef BOOST_USE_UCONTEXT
 cycle_t test_ucontext_cycle( cycle_t ov)
 {
     ctx::stack_allocator alloc;
 
     ::getcontext( & uc);
-    uc.uc_stack.ss_sp = 
-        static_cast< char * >( alloc.allocate(ctx::default_stacksize() ) )
-        - ctx::default_stacksize();
+    uc.uc_stack.ss_sp = alloc.allocate(ctx::default_stacksize());
     uc.uc_stack.ss_size = ctx::default_stacksize();
     ::makecontext( & uc, f2, 7);
 
@@ -110,22 +111,16 @@
 
     return total;
 }
-#endif
+# endif
 
-cycle_t test_fcontext_cycle( cycle_t ov)
+cycle_t test_function_cycle( cycle_t ov)
 {
-    ctx::stack_allocator alloc;
-    fc.fc_stack.base = alloc.allocate(ctx::default_stacksize());
-    fc.fc_stack.size = ctx::default_stacksize();
-    ctx::make_fcontext( & fc, f1);
-
-    ctx::jump_fcontext( & fcm, & fc, 7, preserve_fpu);
-
+    boost::function< void() > fn( boost::bind( f3) );
     // cache warum-up
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
 
     cycle_t start( cycles() );
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
     cycle_t total( cycles() - start);
 
     // we have two jumps and two measuremt-overheads
@@ -137,15 +132,22 @@
 }
 #endif
 
+
 #if _POSIX_C_SOURCE >= 199309L
-zeit_t test_function_zeit( zeit_t ov)
+zeit_t test_fcontext_zeit( zeit_t ov)
 {
-    boost::function< void() > fn( boost::bind( f3) );
+    ctx::stack_allocator alloc;
+    fc.fc_stack.sp = alloc.allocate(ctx::default_stacksize());
+    fc.fc_stack.size = ctx::default_stacksize();
+    ctx::make_fcontext( & fc, f1);
+
+    ctx::jump_fcontext( & fcm, & fc, 7, pres_fpu);
+
     // cache warum-up
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
 
     zeit_t start( zeit() );
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
     zeit_t total( zeit() - start);
 
     // we have two jumps and two measuremt-overheads
@@ -156,15 +158,13 @@
     return total;
 }
 
-#ifndef BOOST_WINDOWS
+# ifdef BOOST_USE_UCONTEXT
 zeit_t test_ucontext_zeit( zeit_t ov)
 {
     ctx::stack_allocator alloc;
 
     ::getcontext( & uc);
-    uc.uc_stack.ss_sp = 
-        static_cast< char * >( alloc.allocate(ctx::default_stacksize() ) )
-        - ctx::default_stacksize();
+    uc.uc_stack.ss_sp = alloc.allocate(ctx::default_stacksize());
     uc.uc_stack.ss_size = ctx::default_stacksize();
     ::makecontext( & uc, f2, 7);
 
@@ -182,22 +182,16 @@
 
     return total;
 }
-#endif
+# endif
 
-zeit_t test_fcontext_zeit( zeit_t ov)
+zeit_t test_function_zeit( zeit_t ov)
 {
-    ctx::stack_allocator alloc;
-    fc.fc_stack.base = alloc.allocate(ctx::default_stacksize());
-    fc.fc_stack.size = ctx::default_stacksize();
-    ctx::make_fcontext( & fc, f1);
-
-    ctx::jump_fcontext( & fcm, & fc, 7, preserve_fpu);
-
+    boost::function< void() > fn( boost::bind( f3) );
     // cache warum-up
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
 
     zeit_t start( zeit() );
-BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FCONTEXT, ~)
+BOOST_PP_REPEAT_FROM_TO( 0, BOOST_PP_LIMIT_MAG, CALL_FUNCTION, ~)
     zeit_t total( zeit() - start);
 
     // we have two jumps and two measuremt-overheads
@@ -222,10 +216,10 @@
 
             unsigned int res = test_fcontext_cycle( ov);
             std::cout << "fcontext: average of " << res << " cycles per switch" << std::endl;
-#ifndef BOOST_WINDOWS
+# ifdef BOOST_USE_UCONTEXT
             res = test_ucontext_cycle( ov);
             std::cout << "ucontext: average of " << res << " cycles per switch" << std::endl;
-#endif
+# endif
             res = test_function_cycle( ov);
             std::cout << "boost::function: average of " << res << " cycles per switch" << std::endl;
         }
@@ -238,10 +232,10 @@
 
             unsigned int res = test_fcontext_zeit( ov);
             std::cout << "fcontext: average of " << res << " ns per switch" << std::endl;
-#ifndef BOOST_WINDOWS
+# ifdef BOOST_USE_UCONTEXT
             res = test_ucontext_zeit( ov);
             std::cout << "ucontext: average of " << res << " ns per switch" << std::endl;
-#endif
+# endif
             res = test_function_zeit( ov);
             std::cout << "boost::function: average of " << res << " ns per switch" << std::endl;
         }

Modified: trunk/libs/context/src/asm/fcontext_arm_aapcs_elf_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_arm_aapcs_elf_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_arm_aapcs_elf_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -26,7 +26,7 @@
  *  -------------------------------------------------------------  *
  *  | 0x2c| 0x30|                                               |  *
  *  -------------------------------------------------------------  *
- *  |sbase|slimit|                                              |  *
+ *  |  sp | size|                                               |  *
  *  -------------------------------------------------------------  *
  *  -------------------------------------------------------------  *
  *  |  13 |  14 | 15 |  16 |  17 |  18 |  19 |  20 |  21 |  22  |  *
@@ -79,6 +79,8 @@
 make_fcontext:
     str     a2, [a1,#40]        @ save address of context function
     ldr     a2, [a1,#44]        @ load address of context stack base
+    ldr     a3, [a1,#48]        @ load size of context stack
+    add     a2, a3              @ compute start address of context stack
 
     push    {a1,lr}             @ save pointer to fcontext_t
     mov     a1, a2              @ context stack pointer as arg for align_stack

Modified: trunk/libs/context/src/asm/fcontext_i386_ms_pe_masm.asm
==============================================================================
--- trunk/libs/context/src/asm/fcontext_i386_ms_pe_masm.asm	(original)
+++ trunk/libs/context/src/asm/fcontext_i386_ms_pe_masm.asm	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -16,7 +16,7 @@
 ;  --------------------------------------------------------------
 ;  |   018h  |   01ch  |   020h  |                              |
 ;  --------------------------------------------------------------
-;  |   base  |  limit  |   size  |                              |
+;  |    sp   |   size  |   base  |                              |
 ;  --------------------------------------------------------------
 ;  --------------------------------------------------------------
 ;  |    9    |                                                  |
@@ -61,9 +61,9 @@
     mov     eax,         [edx]      ; load current SEH exception list
     mov     [ecx+024h],  eax        ; save current exception list
     mov     eax,         [edx+04h]  ; load current stack base
-    mov     [ecx+018h],  eax        ; save current stack base
+    mov     [ecx+020h],  eax        ; save current stack base
     mov     eax,         [edx+08h]  ; load current stack limit
-    mov     [ecx+01ch],  eax        ; save current stack limit
+    mov     [ecx+018h],  eax        ; save current stack limit
     mov     eax,         [edx+010h] ; load fiber local storage
     mov     [ecx+028h],  eax        ; save fiber local storage
 
@@ -93,9 +93,9 @@
     assume  fs:error
     mov     eax,        [ecx+024h]  ; load SEH exception list
     mov     [edx],      eax         ; restore next SEH item
-    mov     eax,        [ecx+018h]  ; load stack base
+    mov     eax,        [ecx+020h]  ; load stack base
     mov     [edx+04h],  eax         ; restore stack base
-    mov     eax,        [ecx+01ch]  ; load stack limit
+    mov     eax,        [ecx+018h]  ; load stack limit
     mov     [edx+08h],  eax         ; restore stack limit
     mov     eax,        [ecx+028h]  ; load fiber local storage
     mov     [edx+010h], eax         ; restore fiber local storage
@@ -110,44 +110,51 @@
 jump_fcontext ENDP
 
 make_fcontext PROC EXPORT
-    mov  eax,         [esp+04h]     ; load address of the fcontext_t
-    mov  ecx,         [esp+08h]     ; load address of the context function
-    mov  [eax+014h],  ecx           ; save address of the context function
-    mov  edx,         [eax+018h]    ; load address of context stack base
-    mov  ecx,         [eax+020h]    ; load context stack size
-    neg  ecx                        ; negate stacksize for LEA 
-    lea  ecx,         [edx+ecx]     ; compute context stack limit
-    mov  [eax+01ch],  ecx           ; save context stack limit
+    push ebp                        ; save previous frame pointer; get the stack 16 byte aligned
+    mov  ebp,         esp           ; set EBP to ESP 
+    sub  esp,         010h          ; allocate stack space
+
+    mov  eax,         [ebp+08h]     ; load address of fcontext_t
+    mov  ecx,         [ebp+0ch]     ; load address of context function
+    mov  [eax+014h],  ecx           ; save address of context function
+    mov  edx,         [eax+018h]    ; load address of context stack (limit)
+    mov  ecx,         [eax+01ch]    ; load context stack size
+    lea  edx,         [edx+ecx]     ; compute top address of context stack (base)
+    mov  [eax+020h],  edx           ; save top address of context stack (base)
 
-    push  eax                       ; save pointer to fcontext_t
-    push  edx                       ; context stack as arg for align_stack
+    mov   [esp+04h],  eax           ; save pointer to fcontext_t
+    mov   [esp],      edx           ; context stack as arg for align_stack
     call  align_stack               ; call align_stack
     mov   edx,        eax           ; begin of aligned context stack
-    pop   eax                       ; remove arg for align_stack
-    pop   eax                       ; restore pointer to fcontext_t
+    mov   eax,        [esp+04h]     ; restore pointer to fcontext_t
+    
+    stmxcsr [eax+02ch]              ; save MMX control word
+    fnstcw  [eax+030h]              ; save x87 control word
 
-    lea  edx,         [edx-014h]    ; reserve space for last frame on context stack, (ESP + 4) & 15 == 0
-    mov  [eax+010h],  edx           ; save the aligned stack
+    lea  edx,         [edx-01ch]    ; reserve space for last frame and seh on context stack, (ESP - 0x4) % 16 == 0
+    mov  [eax+010h],  edx           ; save address in EDX as stack pointer for context stack
 
     mov  ecx,         seh_fcontext  ; set ECX to exception-handler
-    mov  [edx+0ch],   ecx           ; save ECX as SEH handler
+    mov  [edx+018h],  ecx           ; save ECX as SEH handler
     mov  ecx,         0ffffffffh    ; set ECX to -1
-    mov  [edx+08h],   ecx           ; save ECX as next SEH item
-    lea  ecx,         [edx+08h]     ; load address of next SEH item
+    mov  [edx+014h],  ecx           ; save ECX as next SEH item
+    lea  ecx,         [edx+014h]    ; load address of next SEH item
     mov  [eax+024h],  ecx           ; save next SEH
 
-    stmxcsr [eax+02ch]              ; save MMX control word
-    fnstcw  [eax+030h]              ; save x87 control word
+    mov  ecx,         finish        ; abs address of finish
+    mov  [edx],       ecx           ; save address of finish as return address for context function
+                                    ; entered after context function returns
 
-    mov  ecx,         finish        ; address of finish
-    mov  [edx],       ecx
+    add  esp,         010h          ; deallocate stack space
+    pop  ebp
 
     xor  eax,         eax
     ret
 
 finish:
+    ; ESP == stack pointer of context function + 0x4
     xor   eax,        eax
-    push  eax                       ; exit code is zero
+    mov   [esp],      eax           ; exit code is zero
     call  _exit                     ; exit application
     hlt
 make_fcontext ENDP

Modified: trunk/libs/context/src/asm/fcontext_i386_sysv_elf_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_i386_sysv_elf_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_i386_sysv_elf_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -19,7 +19,7 @@
  *  --------------------------------------------------------------  *
  *  |   0x18  |   0x1c  |                                        |  *
  *  --------------------------------------------------------------  *
- *  |  sbase  | slimit  |                                        |  *
+ *  |    sp   |  size   |                                        |  *
  *  --------------------------------------------------------------  *
  *  --------------------------------------------------------------  *
  *  |    8    |    9    |                                        |  *
@@ -76,46 +76,54 @@
 .align 2
 .type make_fcontext,@function
 make_fcontext:
-    movl   0x4(%esp),      %eax         /* load address of the fcontext_t */
-    movl   0x8(%esp),      %ecx         /* load address of the context function */
-    movl   %ecx,           0x14(%eax)   /* save address of the context function */
+    pushl  %ebp                         /* save previous frame pointer; get the stack 16 byte aligned */
+    movl   %esp,           %ebp         /* set EBP to ESP */
+    subl   $0x10,          %esp         /* allocate stack space */
+
+    movl   0x8(%ebp),      %eax         /* load address of fcontext_t */
+    movl   0xc(%ebp),      %ecx         /* load address of context function */
+    movl   %ecx,           0x14(%eax)   /* save address of context function */
     movl   0x18(%eax),     %edx         /* load address of context stack base */
+    movl   0x1c(%eax),     %ecx         /* load size of context stack */
+    leal   (%edx,%ecx),    %edx         /* compute top address of context stack */
 
-    pushl  %eax                         /* save pointer to fcontext_t */
-    pushl  %ebx                         /* save EBX */
-    pushl  %edx                         /* context stack pointer as arg for align_stack */
+    movl  %ebx,            0x8(%esp)    /* save EBX */
+    movl  %eax,            0x4(%esp)    /* save pointer to fcontext_t */
+    movl  %edx,            (%esp)       /* context stack pointer as arg for align_stack */
     call   1f
 1:  popl   %ebx                                    /* address of label 1 */
     addl   $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx     /* compute address of GOT and store it in EBX */
     call   align_stack_at_PLT                         /* call align_stack */
     movl   %eax,           %edx                    /* begin of aligned context stack */
-    popl   %eax                                    /* remove arg for align_stack */
-    popl   %ebx                                    /* restore EBX */
-    popl   %eax                                    /* restore pointer to fcontext_t */
-
-    leal   -0x14(%edx),    %edx         /* reserve space for the last frame on context stack, (ESP + 4) % 16 == 0 */
-    movl   %edx,           0x10(%eax)   /* save the aligned context stack base */
+    movl   0x4(%esp),      %eax                    /* restore pointer to fcontext_t */
+    movl   0x8(%esp),      %ebx                    /* restore EBX */
 
     stmxcsr  0x20(%eax)                 /* save MMX control and status word */
     fnstcw   0x24(%eax)                 /* save x87 control word */
 
-    call    2f
-2:  popl    %ecx                        /* address of label 2 */
-    addl    $finish-2b, %ecx            /* helper code executed after context function returns */
-    movl    %ecx, (%edx)
+    leal   -0xc(%edx),     %edx         /* reserve space for the last frame on context stack; (ESP - 0x4) % 16 == 0 */
+    movl   %edx,           0x10(%eax)   /* save address in EDX as stack pointer for context function */
+
+    call   2f
+2:  popl   %ecx                        /* address of label 2 */
+    addl   $finish-2b, %ecx            /* compute abs address of label finish */
+    movl   %ecx, (%edx)                /* save address of finish as return address for context functions */
+                                       /* entered after context function returns */
 
-    xorl   %eax,            %eax
+    addl   $0x10,          %esp        /* deallocate stack space */
+    pop    %ebp
+
+    xorl    %eax,          %eax
     ret
 
 finish:
-    leal   -0xc(%esp),    %esp
-
+    /* ESP == stack pointer of context function + 0x4 */
     call    3f
 3:  popl    %ebx                                    /* address of label 3 */
     addl    $_GLOBAL_OFFSET_TABLE_+[.-3b], %ebx     /* compute address of GOT and store it in EBX */
 
-    xorl    %eax,           %eax
-    pushl   %eax                        /* exit code is zero */
+    xorl    %eax,  %eax
+    movl    %eax,  (%esp)               /* exit code is zero */
     call   _exit_at_PLT                    /* exit application */
     hlt
 .size make_fcontext,.-make_fcontext

Modified: trunk/libs/context/src/asm/fcontext_i386_sysv_macho_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_i386_sysv_macho_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_i386_sysv_macho_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -19,7 +19,7 @@
  *  --------------------------------------------------------------  *
  *  |   0x18  |   0x1c  |                                        |  *
  *  --------------------------------------------------------------  *
- *  |  sbase  | slimit  |                                        |  *
+ *  |    sp   |   size  |                                        |  *
  *  --------------------------------------------------------------  *
  *  --------------------------------------------------------------  *
  *  |    8    |    9    |                                        |  *
@@ -73,37 +73,44 @@
 .globl _make_fcontext
 .align 2
 _make_fcontext:
-    movl   0x4(%esp),      %eax         /* load address of the fcontext_t */
-    movl   0x8(%esp),      %ecx         /* load address of the context function */
-    movl   %ecx,           0x14(%eax)   /* save address of the context function */
+    pushl  %ebp                         /* save previous frame pointer; get the stack 16 byte aligned */
+    movl   %esp,           %ebp         /* set EBP to ESP */
+    subl   $0x10,          %esp         /* allocate stack space */
+
+    movl   0x8(%ebp),      %eax         /* load address of fcontext_t */
+    movl   0xc(%ebp),      %ecx         /* load address of context function */
+    movl   %ecx,           0x14(%eax)   /* save address of context function */
     movl   0x18(%eax),     %edx         /* load address of context stack base */
+    movl   0x1c(%eax),     %ecx         /* load size of context stack */
+    leal   (%edx,%ecx),    %edx         /* compute top address of context stack */
 
-    pushl  %eax                         /* save pointer to fcontext_t */
-    pushl  %ebx                         /* save EBX */
-    pushl  %edx                         /* context stack pointer as arg for align_stack */
+    movl   %eax,           0x4(%esp)    /* save pointer to fcontext_t */
+    movl   %edx,           (%esp)       /* context stack pointer as arg for align_stack */
     call   _align_stack                 /* call align_stack */
     movl   %eax,           %edx         /* begin of aligned context stack */
-    popl   %eax                         /* remove arg for align_stack */
-    popl   %ebx                         /* restore EBX */
-    popl   %eax                         /* restore pointer to fcontext_t */
-
-    leal   -0x14(%edx),    %edx         /* reserve space for the last frame on context stack, (ESP + 4) % 16 == 0 */
-    movl   %edx,           0x10(%eax)   /* save the aligned context stack base */
+    movl   0x4(%esp),      %eax         /* restore pointer to fcontext_t */
 
     stmxcsr  0x20(%eax)                 /* save MMX control and status word */
     fnstcw   0x24(%eax)                 /* save x87 control word */
 
+    leal   -0xc(%edx),     %edx         /* reserve space for the last frame on context stack, (ESP - 0x4) % 16 == 0 */
+    movl   %edx,           0x10(%eax)   /* save address in EDX as stack pointer for context function */
+
     call   1f
-1:  popl   %ecx                         /* address of lable 1 */
-    addl   $finish-1b,     %ecx         /* helper code executed after context function returns */
-    movl   %ecx, (%edx)
+1:  popl   %ecx                         /* address of label 1 */
+    addl   $finish-1b,     %ecx         /* compute abs address of label finish */
+    movl    %ecx, (%edx)                /* save address of finish as return address for context function */
+                                        /* entered after context function returns */
+
+    addl   $0x10,          %esp         /* deallocate stack space */
+    pop    %ebp
 
     xorl   %eax,           %eax
     ret
 
 finish:
-    leal   -0xc(%esp),    %esp
-    xorl    %eax,           %eax
-    pushl   %eax                        /* exit code is zero */
+    /* ESP == stack pointer of context function + 0x4 */
+    xorl    %eax,  %eax
+    movl    %eax,  (%esp)               /* exit code is zero */
     call   _exit                        /* exit application */
     hlt

Modified: trunk/libs/context/src/asm/fcontext_mips32_o32_elf_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_mips32_o32_elf_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_mips32_o32_elf_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -26,7 +26,7 @@
  *  -------------------------------------------------------------  *
  *  | 104 | 112 |                                               |  *
  *  -------------------------------------------------------------  *
- *  |sbase|slimt|                                               |  *
+ *  |  sp | size|                                               |  *
  *  -------------------------------------------------------------  *
  *  -------------------------------------------------------------  *
  *  |  15 |  16 |  17 |  18 |  19 |  20 |                       |  *
@@ -112,6 +112,8 @@
     sw      $gp, 24($a0)        # save global pointer
     sw      $a1, 96($a0)        # save address of context function
     lw      $t0, 104($a0)       # load address of context stack base
+    lw      $t1, 112($a0)       # load size of context stack
+    add     $t0, $t1, $t0       # compute start address of context stack
 
     sub     $sp, $sp, 28
     sw      $ra, 24($sp)

Modified: trunk/libs/context/src/asm/fcontext_ppc32_sysv_elf_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_ppc32_sysv_elf_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_ppc32_sysv_elf_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -33,7 +33,7 @@
  *  -------------------------------------------------------------  *
  *  |  92 |  96 |                                               |  *
  *  -------------------------------------------------------------  *
- *  |sbase|slimt|                                               |  *
+ *  |  sp | size|                                               |  *
  *  -------------------------------------------------------------  *
  *  -------------------------------------------------------------  *
  *  |  25 |  26 |  27 |  28 |  29 |  30 |  31 |  32 |  33 |  34 |  *
@@ -186,6 +186,8 @@
 make_fcontext:
     stw     %r4, 88(%r3)        # save address of context function
     lwz     %r0, 92(%r3)        # load address of context stack base
+    lwz     %r4, 96(%r3)        # load size of context stack
+    add     %r0, %r4, %r0       # compute start address of context stack
 
     li      %r4, 28
     subf    %r1, %r4, %r1       # reserve space on stack

Modified: trunk/libs/context/src/asm/fcontext_ppc64_sysv_elf_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_ppc64_sysv_elf_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_ppc64_sysv_elf_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -47,7 +47,7 @@
  *  -------------------------------------------------------------  *
  *  | 184 | 188 | 192 | 196 |                                   |  *
  *  -------------------------------------------------------------  *
- *  |   sbase   |   slimt   |                                   |  *
+ *  |    sp     |    size   |                                   |  *
  *  -------------------------------------------------------------  *
  *  -------------------------------------------------------------  *
  *  |  50 |  51 |  52 |  53 |  54 |  55 |  56 |  57 |  58 |  59 |  *
@@ -214,6 +214,8 @@
 .make_fcontext:
     std     %r4, 176(%r3)       # save address of context function
     ld      %r0, 184(%r3)       # load address of context stack base
+    ld      %r4, 192(%r3)       # load size of context stack
+    add     %r0, %r4, %r0       # compute start address of context stack
 
     li      %r4, 56
     subf    %r1, %r4, %r1       # reserve space on stack

Modified: trunk/libs/context/src/asm/fcontext_x86_64_ms_pe_masm.asm
==============================================================================
--- trunk/libs/context/src/asm/fcontext_x86_64_ms_pe_masm.asm	(original)
+++ trunk/libs/context/src/asm/fcontext_x86_64_ms_pe_masm.asm	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -30,7 +30,7 @@
 ;  ----------------------------------------------------------------------------------
 ;  |   0x50  |   0x54  |   0x58  |   0x5c  |   0x60   |   0x64  |                   |
 ;  ----------------------------------------------------------------------------------
-;  |       base        |       limit       |        size        |                   |
+;  |        sp         |       size        |        base        |                   |
 ;  ----------------------------------------------------------------------------------
 ;  ----------------------------------------------------------------------------------
 ;  |    26   |   27    |                                                            |
@@ -101,9 +101,9 @@
 
     mov     r10,         gs:[030h]  ; load NT_TIB
     mov     rax,         [r10+08h]  ; load current stack base
-    mov     [rcx+050h],  rax        ; save current stack base
+    mov     [rcx+060h],  rax        ; save current stack base
     mov     rax,         [r10+010h] ; load current stack limit
-    mov     [rcx+058h],  rax        ; save current stack limit
+    mov     [rcx+050h],  rax        ; save current stack limit
     mov     rax,         [r10+018h] ; load fiber local storage
     mov     [rcx+068h],  rax        ; save fiber local storage
 
@@ -112,7 +112,7 @@
 
     stmxcsr [rcx+070h]              ; save MMX control and status word
     fnstcw  [rcx+074h]              ; save x87 control word
-	mov	    r10,         [rcx+078h] ; address of aligned XMM storage
+    mov     r10,         [rcx+078h] ; address of aligned XMM storage
     movaps  [r10],       xmm6
     movaps  [r10+010h],  xmm7
     movaps  [r10+020h],  xmm8
@@ -126,7 +126,7 @@
 
     ldmxcsr [rdx+070h]              ; restore MMX control and status word
     fldcw   [rdx+074h]              ; restore x87 control word
-	mov	    r10,         [rdx+078h] ; address of aligned XMM storage
+    mov     r10,         [rdx+078h] ; address of aligned XMM storage
     movaps  xmm6,        [r10]
     movaps  xmm7,        [r10+010h]
     movaps  xmm8,        [r10+020h]
@@ -154,9 +154,9 @@
     mov     rbp,        [rdx+038h]  ; restore RBP
 
     mov     r10,        gs:[030h]   ; load NT_TIB
-    mov     rax,        [rdx+050h]  ; load stack base
+    mov     rax,        [rdx+060h]  ; load stack base
     mov     [r10+08h],  rax         ; restore stack base
-    mov     rax,        [rdx+058h]  ; load stack limit
+    mov     rax,        [rdx+050h]  ; load stack limit
     mov     [r10+010h], rax         ; restore stack limit
     mov     rax,        [rdx+068h]  ; load fiber local storage
     mov     [r10+018h], rax         ; restore fiber local storage
@@ -170,40 +170,44 @@
     jmp     r10                     ; indirect jump to caller
 jump_fcontext ENDP
 
-make_fcontext PROC EXPORT FRAME  ; generate function table entry in .pdata and unwind information in    E
+make_fcontext PROC EXPORT FRAME  ; generate function table entry in .pdata and unwind information in
     .endprolog                   ; .xdata for a function's structured exception handling unwind behavior
 
+    push rbp                     ; save previous frame pointer; get the stack 16 byte aligned
+    mov  rbp,        rsp         ; set RBP to RSP
+    sub  rsp,        040h        ; allocate shadow space
+
     mov  [rcx+048h], rdx         ; save address of context function
-    mov  rdx,        [rcx+050h]  ; load address of context stack base
-    mov  r8,         [rcx+060h]  ; load context stack size
-    neg  r8                      ; negate r8 for LEA 
-    lea  r8,         [rdx+r8]    ; compute the address of context stack limit
-    mov  [rcx+058h], r8          ; save the address of context stack limit
+    mov  rdx,        [rcx+050h]  ; load address of context stack pointer (limit)
+    mov  r8,         [rcx+058h]  ; load context stack size
+    lea  rdx,        [rdx+r8]    ; compute top address of context stack (base)
+    mov  [rcx+060h], rdx         ; save top address of context stack (base)
 
-    push  rcx                    ; save pointer to fcontext_t
-    sub   rsp,       028h        ; reserve shadow space for align_stack
+    mov   [rbp-08h], rcx         ; save pointer to fcontext_t
     mov   rcx,       rdx         ; context stack pointer as arg for align_stack
-    mov   [rsp+8],   rcx
     call  align_stack            ; call align_stack
     mov   rdx,       rax         ; begin of aligned context stack
-    add   rsp,       028h
-    pop   rcx                    ; restore pointer to fcontext_t
-
-    lea  rdx,        [rdx-028h]  ; reserve 32byte shadow space + return address on stack, (RSP + 8) % 16 == 0
-    mov  [rcx+040h], rdx         ; save the address where the context stack begins
+    mov   rcx,       [rbp-08h]   ; restore pointer to fcontext_t
 
     stmxcsr [rcx+070h]           ; save MMX control and status word
     fnstcw  [rcx+074h]           ; save x87 control word
 
-    lea  rax,       finish       ; helper code executed after fn() returns
-    mov  [rdx],     rax          ; store address off the helper function as return address
+    lea  rdx,        [rdx-028h]  ; reserve 32byte shadow space + return address on stack, (RSP - 0x8) % 16 == 0
+    mov  [rcx+040h], rdx         ; save address in RDX as stack pointer for context function
+
+    lea  rax,        finish      ; compute abs address of label finish
+    mov  [rdx],      rax         ; save address of finish as return address for context function
+                                 ; entered after context function returns
+
+    add  rsp,        040h        ; deallocate shadow space
+    pop  rbp                     ; restore previous frame pointer
 
-    xor  rax,       rax          ; set RAX to zero
+    xor  rax,        rax
     ret
 
 finish:
-    xor   rcx,        rcx
-    mov   [rsp+08h],  rcx
+    ; RSP == stack pointer in fcontext + 0x8
+    xor   rcx,       rcx         ; exit code is zero
     call  _exit                  ; exit application
     hlt
 make_fcontext ENDP

Modified: trunk/libs/context/src/asm/fcontext_x86_64_sysv_elf_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_x86_64_sysv_elf_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_x86_64_sysv_elf_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -26,7 +26,7 @@
  *  ----------------------------------------------------------------------------------  *
  *  |  0x40   |  0x44   |  0x48   |   0x4c  |                                        |  *
  *  ----------------------------------------------------------------------------------  *
- *  |       sbase       |        slimit     |                                        |  *
+ *  |        sp         |       size        |                                        |  *
  *  ----------------------------------------------------------------------------------  *
  *  ----------------------------------------------------------------------------------  *
  *  |    20   |    21   |                                                            |  *
@@ -86,30 +86,41 @@
 .type make_fcontext,@function
 .align 16
 make_fcontext:
-    movq   %rsi,                 0x38(%rdi) /* save address of context function */
-    movq   0x40(%rdi),           %rdx       /* load address of context stack base */
+    pushq   %rbp                       /* save previous frame pointer; get the stack 16 byte aligned */
+    movq    %rsp,           %rbp       /* set RBP to RSP */
+    subq    $0x10,          %rsp       /* allocate stack space */ 
+
+    movq   %rsi,            0x38(%rdi) /* save address of context function */
+    movq   0x40(%rdi),      %rdx       /* load address of context stack base */
+    movq   0x48(%rdi),      %rax       /* load size of context stack */
+    leaq   (%rdx,%rax),     %rdx       /* compute top address of context stack */
+
+    movq   %rdi,            (%rsp)     /* save pointer to fcontext_t */
+    movq   %rdx,            %rdi       /* context stack pointer as arg for align_stack */
+    call   align_stack_at_PLT             /* align context stack */
+    movq   %rax,            %rdx       /* begin of aligned context stack */
+    movq   (%rsp),          %rdi       /* restore pointer to fcontext_t */
+
+    stmxcsr  0x50(%rdi)                /* save MMX control and status word */
+    fnstcw   0x54(%rdi)                /* save x87 control word */
+
+    leaq   -0x8(%rdx),      %rdx       /* reserve space for the last frame on context stack, (RSP - 0x8) % 16 == 0 */
+    movq   %rdx,            0x30(%rdi) /* save address in RDX as stack pointer for context function */
+
+    leaq   finish(%rip),    %rcx       /* compute abs address of label finish */
+    movq   %rcx,            (%rdx)     /* save address of finish as return address for context function */
+                                       /* entered after context function returns */
 
-    pushq  %rdi                             /* save pointer to fcontext_t */
-    movq   %rdx,                 %rdi       /* context stack pointer as arg for align_stack */
-    call   align_stack_at_PLT                  /* align context stack */
-    movq   %rax,                 %rdx       /* begin of aligned context stack */
-    popq   %rdi                             /* restore pointer to fcontext_t */
+    addq   $0x10,           %rsp       /* deallocate shadow space */      
+    popq   %rbp                        /* restore previous frame pointer */
 
-    leaq   -0x8(%rdx),           %rdx       /* reserve space for the last frame on context stack, (RSP + 8) & 15 == 0 */
-    movq   %rdx,                 0x30(%rdi) /* save the algined context stack base */
-
-    stmxcsr  0x50(%rdi)                     /* save MMX control and status word */
-    fnstcw   0x54(%rdi)                     /* save x87 control word */
-
-    leaq   finish(%rip),         %rcx       /* address of finish; called after context function returns */
-    movq   %rcx,                 (%rdx)
-
-    xorq   %rax,                 %rax
+    xorq   %rax,            %rax
     ret
 
 finish:
-    xorq    %rdi,              %rdi         /* exit code is zero */
-    call   _exit_at_PLT                        /* exit application */
+    /* RSP == stack pointer of context function + 0x8 */
+    xorq    %rdi,           %rdi       /* exit code is zero */
+    call   _exit_at_PLT                   /* exit application */
     hlt
 .size make_fcontext,.-make_fcontext
 

Modified: trunk/libs/context/src/asm/fcontext_x86_64_sysv_macho_gas.S
==============================================================================
--- trunk/libs/context/src/asm/fcontext_x86_64_sysv_macho_gas.S	(original)
+++ trunk/libs/context/src/asm/fcontext_x86_64_sysv_macho_gas.S	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -26,7 +26,7 @@
  *  ----------------------------------------------------------------------------------  *
  *  |  0x40   |  0x44   |  0x48   |   0x4c  |                                        |  *
  *  ----------------------------------------------------------------------------------  *
- *  |       sbase       |        slimit     |                                        |  *
+ *  |        sp         |        size       |                                        |  *
  *  ----------------------------------------------------------------------------------  *
  *  ----------------------------------------------------------------------------------  *
  *  |    20   |    21   |                                                            |  *
@@ -83,28 +83,39 @@
 .globl _make_fcontext
 .align 8
 _make_fcontext:
-    movq   %rsi,                 0x38(%rdi) /* save address of context function */
-    movq   0x40(%rdi),           %rdx       /* load address of context stack base */
+    pushq   %rbp                       /* save previous frame pointer; get the stack 16 byte aligned */
+    movq    %rsp,           %rbp       /* set RBP to RSP */
+    subq    $0x10,          %rsp       /* allocate stack space */ 
+
+    movq   %rsi,            0x38(%rdi) /* save address of context function */
+    movq   0x40(%rdi),      %rdx       /* load address of context stack base */
+    movq   0x48(%rdi),      %rax       /* load size of context stack */
+    leaq   (%rdx,%rax),     %rdx       /* compute top address of context stack */
+
+    movq   %rdi,            (%rsp)     /* save pointer to fcontext_t */
+    movq   %rdx,            %rdi       /* context stack pointer as arg for align_stack */
+    call   _align_stack                /* call align_stack */
+    movq   %rax,            %rdx       /* begin of aligned context stack */
+    movq   (%rsp),          %rdi       /* restore pointer to fcontext_t */
+
+    stmxcsr  0x50(%rdi)                /* save MMX control and status word */
+    fnstcw   0x54(%rdi)                /* save x87 control word */
+
+    leaq   -0x8(%rdx),      %rdx       /* reserve space for the last frame on context stack, (RSP - 0x8) % 16 == 0 */
+    movq   %rdx,            0x30(%rdi) /* save address in RDX as stack pointer for context function */
+
+    leaq   finish(%rip),    %rcx       /* compute abs address of label finish */
+    movq   %rcx,            (%rdx)     /* save address of finish as return address for context function */
+                                       /* entered after context function returns */
 
-    pushq  %rdi                             /* save pointer to fcontext_t */
-    movq   %rdx,                 %rdi       /* context stack pointer as arg for align_stack */
-    call   _align_stack                     /* call align_stack */
-    movq   %rax,                 %rdx       /* begin of aligned context stack */
-    popq   %rdi                             /* restore pointer to fcontext_t */
+    addq   $0x10,           %rsp       /* deallocate shadow space */      
+    popq   %rbp                        /* restore previous frame pointer */
 
-    leaq   -0x8(%rdx),           %rdx       /* reserve space for the last frame on context stack, (RSP + 8) % 16 == 0 */
-    movq   %rdx,                 0x30(%rdi) /* save the algined context stack base */
-
-    stmxcsr  0x50(%rdi)                     /* save MMX control and status word */
-    fnstcw   0x54(%rdi)                     /* save x87 control word */
-
-    leaq   finish(%rip),         %rcx       /* helper code executed after context function returns */
-    movq   %rcx,                 (%rdx)
-
-    xorq   %rax,                 %rax       /* set RAX to zero */
+    xorq   %rax,            %rax
     ret
 
 finish:
-    xorq    %rdi,              %rdi         /* exit code is zero */
-    call   _exit                            /* exit application */
+    /* RSP == stack pointer of context function + 0x8 */
+    xorq    %rdi,           %rdi       /* exit code is zero */
+    call   _exit                       /* exit application */
     hlt

Modified: trunk/libs/context/src/stack_allocator_posix.cpp
==============================================================================
--- trunk/libs/context/src/stack_allocator_posix.cpp	(original)
+++ trunk/libs/context/src/stack_allocator_posix.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -44,8 +44,10 @@
             boost::str( boost::format("invalid stack size: must not be larger than %d bytes")
                 % maximum_stacksize() ) );
 
-    const std::size_t pages( page_count( size) + 1); // add +1 for guard page
-    std::size_t size_ = pages * pagesize();
+    const std::size_t pages( page_count( size) );
+    BOOST_ASSERT( 2 <= pages); // one page is reserved for protection
+    const std::size_t size_( pages * pagesize() );
+    BOOST_ASSERT( 0 < size && 0 < size_);
 
     const int fd( ::open("/dev/zero", O_RDONLY) );
     BOOST_ASSERT( -1 != fd);
@@ -61,7 +63,7 @@
     const int result( ::mprotect( limit, pagesize(), PROT_NONE) );
     BOOST_ASSERT( 0 == result);
 
-    return static_cast< char * >( limit) + size_;
+    return limit;
 }
 
 void
@@ -69,11 +71,10 @@
 {
     if ( vp)
     {
-        const std::size_t pages( page_count( size) + 1); // add +1 for guard page
-        std::size_t size_ = pages * pagesize();
+        const std::size_t pages = page_count( size);
+        const std::size_t size_ = pages * pagesize();
         BOOST_ASSERT( 0 < size && 0 < size_);
-        void * limit = static_cast< char * >( vp) - size_;
-        ::munmap( limit, size_);
+        ::munmap( vp, size_);
     }
 }
 

Modified: trunk/libs/context/src/stack_allocator_windows.cpp
==============================================================================
--- trunk/libs/context/src/stack_allocator_windows.cpp	(original)
+++ trunk/libs/context/src/stack_allocator_windows.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -46,10 +46,11 @@
             boost::str( boost::format("invalid stack size: must not be larger than %d bytes")
                 % maximum_stacksize() ) );
 
-    const std::size_t pages( page_count( size) + 1); // add +1 for guard page
-    std::size_t size_ = pages * pagesize();
+    const std::size_t pages( page_count( size) );
+    BOOST_ASSERT( 2 <= pages); // one page is reserved for protection
+    const std::size_t size_ = pages * pagesize();
+    BOOST_ASSERT( 0 < size && 0 < size_);
 
-#ifndef BOOST_CONTEXT_FIBER
     void * limit = ::VirtualAlloc( 0, size_, MEM_COMMIT, PAGE_READWRITE);
     if ( ! limit) throw std::bad_alloc();
 
@@ -58,8 +59,7 @@
         limit, pagesize(), PAGE_READWRITE | PAGE_GUARD /*PAGE_NOACCESS*/, & old_options);
     BOOST_ASSERT( FALSE != result);
 
-    return static_cast< char * >( limit) + size_;
-#endif
+    return limit;
 }
 
 void
@@ -67,11 +67,10 @@
 {
     if ( vp)
     {
-        const std::size_t pages( page_count( size) + 1); // add +1 for guard page
-        std::size_t size_ = pages * pagesize();
+        const std::size_t pages = page_count( size);
+        const std::size_t size_ = pages * pagesize();
         BOOST_ASSERT( 0 < size && 0 < size_);
-        void * limit = static_cast< char * >( vp) - size_;
-        ::VirtualFree( limit, 0, MEM_RELEASE);
+        ::VirtualFree( vp, 0, MEM_RELEASE);
     }
 }
 

Modified: trunk/libs/context/src/stack_utils_posix.cpp
==============================================================================
--- trunk/libs/context/src/stack_utils_posix.cpp	(original)
+++ trunk/libs/context/src/stack_utils_posix.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -6,6 +6,8 @@
 
 #define BOOST_CONTEXT_SOURCE
 
+#include <algorithm>
+
 #include <boost/context/stack_utils.hpp>
 
 extern "C" {
@@ -39,21 +41,41 @@
     return limit;
 }
 
+static std::size_t compute_default_stacksize_()
+{
+    std::size_t size = 256 * 1024; // 256 kB
+    if ( boost::ctx::is_stack_unbound() )
+        return std::max( size, boost::ctx::minimum_stacksize() );
+    
+    BOOST_ASSERT( boost::ctx::maximum_stacksize() >= boost::ctx::minimum_stacksize() );
+    return boost::ctx::maximum_stacksize() == boost::ctx::minimum_stacksize()
+        ? boost::ctx::minimum_stacksize()
+        : std::min( size, boost::ctx::maximum_stacksize() );
+}
+
 }
 
 namespace boost {
 namespace ctx {
 
 BOOST_CONTEXT_DECL
-std::size_t default_stacksize()
+std::size_t pagesize()
 {
-    static std::size_t size = 256 * 1024;
+    static std::size_t size = ::getpagesize();
     return size;
 }
 
 BOOST_CONTEXT_DECL
-std::size_t minimum_stacksize()
-{ return SIGSTKSZ; }
+std::size_t page_count( std::size_t stacksize)
+{
+    return static_cast< std::size_t >( 
+        std::ceil(
+            static_cast< float >( stacksize) / pagesize() ) );
+}
+
+BOOST_CONTEXT_DECL
+bool is_stack_unbound()
+{ return RLIM_INFINITY == stacksize_limit().rlim_max; }
 
 BOOST_CONTEXT_DECL
 std::size_t maximum_stacksize()
@@ -63,22 +85,18 @@
 }
 
 BOOST_CONTEXT_DECL
-bool is_stack_unbound()
-{ return RLIM_INFINITY == stacksize_limit().rlim_max; }
-
-BOOST_CONTEXT_DECL
-std::size_t pagesize()
+std::size_t minimum_stacksize()
 {
-    static std::size_t pagesize( ::getpagesize() );
-    return pagesize;
+    // space for guard page added
+    static std::size_t size = SIGSTKSZ + pagesize();
+    return size;
 }
 
 BOOST_CONTEXT_DECL
-std::size_t page_count( std::size_t stacksize)
+std::size_t default_stacksize()
 {
-    return static_cast< std::size_t >( 
-        std::ceil(
-            static_cast< float >( stacksize) / pagesize() ) );
+    static std::size_t size = compute_default_stacksize_();
+    return size;
 }
 
 }}

Modified: trunk/libs/context/src/stack_utils_windows.cpp
==============================================================================
--- trunk/libs/context/src/stack_utils_windows.cpp	(original)
+++ trunk/libs/context/src/stack_utils_windows.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -5,6 +5,7 @@
 //          http://www.boost.org/LICENSE_1_0.txt)
 
 #define BOOST_CONTEXT_SOURCE
+#define NOMINMAX
 
 #include <boost/context/stack_utils.hpp>
 
@@ -32,53 +33,67 @@
     return si;
 }
 
+static std::size_t compute_default_stacksize_()
+{
+    std::size_t size = 256 * 1024; // 256 kB
+    if ( boost::ctx::is_stack_unbound() )
+        return std::max( size, boost::ctx::minimum_stacksize() );
+    
+    BOOST_ASSERT( boost::ctx::maximum_stacksize() >= boost::ctx::minimum_stacksize() );
+    return boost::ctx::maximum_stacksize() == boost::ctx::minimum_stacksize()
+        ? boost::ctx::minimum_stacksize()
+        : std::min( size, boost::ctx::maximum_stacksize() );
+}
+
 }
 
 namespace boost {
 namespace ctx {
 
 BOOST_CONTEXT_DECL
-std::size_t default_stacksize()
+std::size_t pagesize()
 {
-    static std::size_t size = 256 * 1024;
+    static std::size_t size =
+        static_cast< std::size_t >( system_info().dwPageSize);
     return size;
 }
 
 BOOST_CONTEXT_DECL
-std::size_t minimum_stacksize()
+std::size_t page_count( std::size_t stacksize)
 {
-    static std::size_t stacksize(
-        static_cast< std::size_t >( system_info().dwAllocationGranularity) );
-    return stacksize;
+    return static_cast< std::size_t >(
+        std::ceil(
+            static_cast< float >( stacksize) / pagesize() ) );
 }
 
+// Windows seams not to provide a limit for the stacksize
+BOOST_CONTEXT_DECL
+bool is_stack_unbound()
+{ return true; }
+
 BOOST_CONTEXT_DECL
 std::size_t maximum_stacksize()
 {
     BOOST_ASSERT( ! is_stack_unbound() );
-    static std::size_t stacksize = 8 * 1024 * 1024;
-    return stacksize;
+    static std::size_t size = 1 * 1024 * 1024 * 1024; // 1GB
+    return size;
 }
 
-// Windows seams not to provide a limit for the stacksize
-BOOST_CONTEXT_DECL
-bool is_stack_unbound()
-{ return true; }
-
 BOOST_CONTEXT_DECL
-std::size_t pagesize()
+std::size_t minimum_stacksize()
 {
-    static std::size_t pagesize(
-        static_cast< std::size_t >( system_info().dwPageSize) );
-    return pagesize;
+    // space for guard page added
+    static std::size_t size =
+        static_cast< std::size_t >( system_info().dwAllocationGranularity)
+        + pagesize();
+    return size;
 }
 
 BOOST_CONTEXT_DECL
-std::size_t page_count( std::size_t stacksize)
+std::size_t default_stacksize()
 {
-    return static_cast< std::size_t >(
-        std::ceil(
-            static_cast< float >( stacksize) / pagesize() ) );
+    static std::size_t size = compute_default_stacksize_();
+    return size;
 }
 
 }}

Modified: trunk/libs/context/test/test_context.cpp
==============================================================================
--- trunk/libs/context/test/test_context.cpp	(original)
+++ trunk/libs/context/test/test_context.cpp	2012-08-31 15:50:07 EDT (Fri, 31 Aug 2012)
@@ -74,13 +74,20 @@
     ctx::jump_fcontext( & fc1, & fcm, 0);
 }
 
+void test_stack_utils()
+{
+    if ( ! ctx::is_stack_unbound() )
+        BOOST_CHECK( ctx::maximum_stacksize() >= ctx::default_stacksize() );
+    BOOST_CHECK( ctx::default_stacksize() >= ctx::minimum_stacksize() );
+}
+
 void test_start()
 {
     value1 = 0;
 
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     ctx::make_fcontext( & fc1, f1);
 
@@ -95,7 +102,7 @@
 
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     ctx::make_fcontext( & fc1, f3);
 
@@ -110,7 +117,7 @@
 {
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     ctx::make_fcontext( & fc1, f4);
 
@@ -122,7 +129,7 @@
 {
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     int i = 7;
     ctx::make_fcontext( & fc1, f5);
@@ -135,7 +142,7 @@
 {
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     std::pair< int, int > data = std::make_pair( 3, 7);
     ctx::make_fcontext( & fc1, f6);
@@ -151,7 +158,7 @@
 {
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     const char * what = "hello world";
     ctx::make_fcontext( & fc1, f7);
@@ -164,7 +171,7 @@
 {
     ctx::stack_allocator alloc;
 
-    fc1.fc_stack.base = alloc.allocate( ctx::minimum_stacksize() );
+    fc1.fc_stack.sp = alloc.allocate( ctx::minimum_stacksize() );
     fc1.fc_stack.size = ctx::minimum_stacksize();
     double d = 7.13;
     ctx::make_fcontext( & fc1, f8);
@@ -178,6 +185,7 @@
     boost::unit_test::test_suite * test =
         BOOST_TEST_SUITE("Boost.Context: context test suite");
 
+    test->add( BOOST_TEST_CASE( & test_stack_utils) );
     test->add( BOOST_TEST_CASE( & test_start) );
     test->add( BOOST_TEST_CASE( & test_jump) );
     test->add( BOOST_TEST_CASE( & test_result) );