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Subject: [Boost-commit] svn:boost r83958 - in trunk: boost/config boost/config/compiler libs/config/doc libs/config/doc/html libs/config/doc/html/boost_config libs/config/test
From: john_at_[hidden]
Date: 2013-04-18 13:50:19

Author: johnmaddock
Date: 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
New Revision: 83958
URL: http://svn.boost.org/trac/boost/changeset/83958

Log:
Apply patch from #8408.
Fixes #8408.
Added:
   trunk/libs/config/test/boost_fallthrough_test.cpp (contents, props changed)
Text files modified:
   trunk/boost/config/compiler/clang.hpp | 10 ++++++++
   trunk/boost/config/suffix.hpp | 10 ++++++++
   trunk/libs/config/doc/html/boost_config/boost_macro_reference.html | 48 ++++++++++++++++++++++++++++++++++++++++
   trunk/libs/config/doc/html/index.html | 2
   trunk/libs/config/doc/macro_reference.qbk | 35 +++++++++++++++++++++++++++++
   trunk/libs/config/test/Jamfile.v2 | 1
   trunk/libs/config/test/config_info.cpp | 22 -----------------
   7 files changed, 106 insertions(+), 22 deletions(-)

Modified: trunk/boost/config/compiler/clang.hpp
==============================================================================
--- trunk/boost/config/compiler/clang.hpp (original)
+++ trunk/boost/config/compiler/clang.hpp 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -38,6 +38,16 @@
# define BOOST_SYMBOL_VISIBLE __attribute__((__visibility__("default")))
#endif

+//
+// The BOOST_FALLTHROUGH macro can be used to annotate implicit fall-through
+// between switch labels.
+//
+#if __cplusplus >= 201103L && defined(__has_warning)
+# if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+# define BOOST_FALLTHROUGH [[clang::fallthrough]]
+# endif
+#endif
+
#if !__has_feature(cxx_auto_type)
# define BOOST_NO_CXX11_AUTO_DECLARATIONS
# define BOOST_NO_CXX11_AUTO_MULTIDECLARATIONS

Modified: trunk/boost/config/suffix.hpp
==============================================================================
--- trunk/boost/config/suffix.hpp (original)
+++ trunk/boost/config/suffix.hpp 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -883,6 +883,16 @@
# define BOOST_NOEXCEPT_IF(Predicate) noexcept((Predicate))
# define BOOST_NOEXCEPT_EXPR(Expression) noexcept((Expression))
#endif
+//
+// Helper macro BOOST_FALLTHROUGH
+// Fallback definition of BOOST_FALLTHROUGH macro used to mark intended
+// fall-through between case labels in a switch statement. We use a definition
+// that requires a semicolon after it to avoid at least one type of misuse even
+// on unsupported compilers.
+//
+#ifndef BOOST_FALLTHROUGH
+# define BOOST_FALLTHROUGH ((void)0)
+#endif

//
// constexpr workarounds

Modified: trunk/libs/config/doc/html/boost_config/boost_macro_reference.html
==============================================================================
--- trunk/libs/config/doc/html/boost_config/boost_macro_reference.html (original)
+++ trunk/libs/config/doc/html/boost_config/boost_macro_reference.html 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -3384,6 +3384,54 @@
<tr>
<td>
 
+ <code class="computeroutput">BOOST_FALLTHROUGH</code>
+ 
+ </td>
+<td>
+ 
+ The BOOST_FALLTHROUGH macro can be used to annotate implicit fall-through
+ between switch labels:
+
+<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting">switch (x) {
+case 40:
+case 41:
+ if (truth_is_out_there) {
+ ++x;
+ BOOST_FALLTHROUGH; // Use instead of/along with annotations in 
+ // comments. 
+ } else {
+ return x;
+ }
+ case 42:
+ ...
+</pre>
+
+ As shown in the example above, the BOOST_FALLTHROUGH macro should
+ be followed by a semicolon. It is designed to mimic control-flow
+ statements like 'break;', so it can be placed in most places where
+ 'break;' can, but only if there are no statements on the execution
+ path between it and the next switch label.
+ 
+ 
+ When compiled with Clang >3.2 in C++11 mode, the BOOST_FALLTHROUGH
+ macro is expanded to <code class="computeroutput">[[clang::fallthrough]]</code>
+ attribute, which is analysed when performing switch labels fall-through
+ diagnostic ('-Wimplicit-fallthrough'). See clang <a href="http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough" target="_top">documentation
+ on language extensions for details.</a>
+ 
+ 
+ When used with unsupported compilers, the BOOST_FALLTHROUGH macro
+ has no effect on diagnostics.
+ 
+ 
+ In either case this macro has no effect on runtime behavior and
+ performance of code.
+ 
+ </td>
+</tr>
+<tr>
+<td>
+ 
 <code class="computeroutput">BOOST_EXPLICIT_TEMPLATE_TYPE(t)</code> <code class="computeroutput">BOOST_EXPLICIT_TEMPLATE_NON_TYPE(t,v)</code> <code class="computeroutput">BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t)</code> <code class="computeroutput">BOOST_APPEND_EXPLICIT_TEMPLATE_NON_TYPE(t,v)</code>
 
 </td>

Modified: trunk/libs/config/doc/html/index.html
==============================================================================
--- trunk/libs/config/doc/html/index.html (original)
+++ trunk/libs/config/doc/html/index.html 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -951,7 +951,7 @@
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left">Last revised: February 19, 2013 at 16:25:18 GMT</td>
+<td align="left">Last revised: April 18, 2013 at 17:44:14 GMT</td>
<td align="right"><div class="copyright-footer"></div></td>
</tr></table>
<hr>

Modified: trunk/libs/config/doc/macro_reference.qbk
==============================================================================
--- trunk/libs/config/doc/macro_reference.qbk (original)
+++ trunk/libs/config/doc/macro_reference.qbk 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -862,6 +862,41 @@
Normally evaluates to nothing, but evaluates to return x; if the compiler
requires a return, even when it can never be reached.
]]
+[[`BOOST_FALLTHROUGH`][
+The BOOST_FALLTHROUGH macro can be used to annotate implicit fall-through
+between switch labels:
+``
+ switch (x) {
+ case 40:
+ case 41:
+ if (truth_is_out_there) {
+ ++x;
+ BOOST_FALLTHROUGH; // Use instead of/along with annotations in
+ // comments.
+ } else {
+ return x;
+ }
+ case 42:
+ ...
+``
+As shown in the example above, the BOOST_FALLTHROUGH macro should be
+followed by a semicolon. It is designed to mimic control-flow statements
+like 'break;', so it can be placed in most places where 'break;' can, but
+only if there are no statements on the execution path between it and the
+next switch label.
+
+When compiled with Clang >3.2 in C++11 mode, the BOOST_FALLTHROUGH macro is
+expanded to `[[clang::fallthrough]]` attribute, which is analysed when
+performing switch labels fall-through diagnostic ('-Wimplicit-fallthrough').
+See clang [@http://clang.llvm.org/docs/LanguageExtensions.html#clang__fallthrough
+documentation on language extensions for details.]
+
+When used with unsupported compilers, the BOOST_FALLTHROUGH macro has no
+effect on diagnostics.
+
+In either case this macro has no effect on runtime behavior and performance
+of code.
+]]
[[`BOOST_EXPLICIT_TEMPLATE_TYPE(t)`
`BOOST_EXPLICIT_TEMPLATE_NON_TYPE(t,v)`
`BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(t)`

Modified: trunk/libs/config/test/Jamfile.v2
==============================================================================
--- trunk/libs/config/test/Jamfile.v2 (original)
+++ trunk/libs/config/test/Jamfile.v2 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -65,4 +65,5 @@
 ]
 [ compile-fail threads/test_thread_fail1.cpp ]
 [ compile-fail threads/test_thread_fail2.cpp ]
+ [ compile boost_fallthrough_test.cpp : <toolset>clang:<cxxflags>"-std=c++11 -Wimplicit-fallthrough" <warnings-as-errors>on <warnings>all ]
 ;

Added: trunk/libs/config/test/boost_fallthrough_test.cpp
==============================================================================
--- (empty file)
+++ trunk/libs/config/test/boost_fallthrough_test.cpp 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -0,0 +1,20 @@
+// Use, modification and distribution are subject to 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)
+
+#include <boost/config.hpp>
+
+int test(int n)
+{
+ switch (n)
+ {
+ case 0:
+ n++;
+ BOOST_FALLTHROUGH;
+ case 1:
+ n++;
+ break;
+ }
+ return n;
+}
+

Modified: trunk/libs/config/test/config_info.cpp
==============================================================================
--- trunk/libs/config/test/config_info.cpp (original)
+++ trunk/libs/config/test/config_info.cpp 2013-04-18 13:50:17 EDT (Thu, 18 Apr 2013)
@@ -1100,27 +1100,6 @@
    PRINT_MACRO(BOOST_NO_USING_TEMPLATE);
    PRINT_MACRO(BOOST_NO_VOID_RETURNS);

-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
    // END GENERATED BLOCK

    PRINT_MACRO(BOOST_INTEL);
@@ -1132,6 +1111,7 @@
    PRINT_MACRO(BOOST_STATIC_CONSTEXPR);
    PRINT_MACRO(BOOST_NOEXCEPT);
    PRINT_MACRO(BOOST_FORCEINLINE);
+ PRINT_MACRO(BOOST_FALLTHROUGH);
}

void print_separator()

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