[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

 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
 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

         template<class Source>
         struct lcast_src_length_integral
             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
             BOOST_STATIC_CONSTANT(std::size_t, value = 156);
             BOOST_STATIC_ASSERT(sizeof(Source) * CHAR_BIT <= 256);

 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>
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