[Boost-bugs] [Boost C++ Libraries] #5631: nvcc's pre-processor breaks boost/lexical_cast.hpp

Subject: [Boost-bugs] [Boost C++ Libraries] #5631: nvcc's pre-processor breaks boost/lexical_cast.hpp
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-06-22 15:51:31

#5631: nvcc's pre-processor breaks boost/lexical_cast.hpp
---------------------------------------------+------------------------------
 Reporter:  Rich Wareham <rjw57@…>           |       Owner:  nasonov     
     Type:  Bugs                             |      Status:  new         
Milestone:  To Be Determined                 |   Component:  lexical_cast
  Version:  Boost 1.42.0                     |    Severity:  Problem     
 Keywords:  nvcc lexical_cast pre-processor  |  
---------------------------------------------+------------------------------
 The `nvcc` compiler fails to compile a trivial file which just `#include`s
 the `boost/lexical_cast.hpp` header. `g++` compiles the file correctly.

 {{{
 rjw57_at_spica:~$ cat foo.cpp
 #include <boost/lexical_cast.hpp>
 rjw57_at_spica:~$ cat foo.cu
 #include <boost/lexical_cast.hpp>
 rjw57_at_spica:~$ /usr/bin/g++-4.4 -c foo.cpp
 rjw57_at_spica:~$ /usr/bin/nvcc --compiler-bindir=/usr/bin/g++-4.4 -c foo.cu
 /usr/include/boost/lexical_cast.hpp(352): error: expected an expression

 1 error detected in the compilation of
 "/tmp/tmpxft_00001520_00000000-4_foo.cpp1.ii".
 }}}

 The problem is with `nvcc`'s pre-processor which can be observed by using
 `-E` and grepping for `// == 1` in the output:

 {{{
 rjw57_at_spica:~$ /usr/bin/g++-4.4 -E -o foo-gcc.i foo.cpp
 rjw57_at_spica:~$ /usr/bin/nvcc --compiler-bindir=/usr/bin/g++-4.4 -E -o foo-
 nvcc.i foo.cu
 rjw57_at_spica:~$ ack-grep '\/\/ == 1' foo*.i
 foo-nvcc.i
 73304:            static const std::size_t value =
 std::numeric_limits<Source>::is_signed +
 std::numeric_limits<Source>::is_specialized + // == 1
 std::numeric_limits<Source>::digits10 * 2;
 }}}

 The `nvcc` pre-processor does not strip comments from the input to the
 compiler and appears to be removing new-lines. The `gcc` compiler does
 strip the comments.

 This is possibly a bug in `nvcc` but I suggest a workaround could be put
 into boost itself without too much pain. Also I suspect it'd take a
 standards lawyer to work out who is in the wrong here.

 The troublesome line (number 345 in 1.4.2) is in the
 `boost/lexical_cast.hpp` file. This problem is still present in the SVN
 trunk.

 {{{
 ...
         template<class Source>
         struct lcast_src_length_integral
         {
 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
             BOOST_STATIC_CONSTANT(std::size_t, value =
                   std::numeric_limits<Source>::is_signed +
                   std::numeric_limits<Source>::is_specialized + // == 1
                   std::numeric_limits<Source>::digits10 * 2
               );
 #else
             BOOST_STATIC_CONSTANT(std::size_t, value = 156);
             BOOST_STATIC_ASSERT(sizeof(Source) * CHAR_BIT <= 256);
 #endif
         };
 ...
 }}}

 A suggested workaround is removing the C++-style comment or replacing it
 with a C-style one?

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5631>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.