boost 1_43_0 BOOST_MPL_ASSERT compile error (gcc 4.2)

[Jeff Epler <jepler@…>]

The simple version:

#include <boost/mpl/assert.hpp>
int main() { BOOST_MPL_ASSERT((1)); BOOST_MPL_ASSERT((1)); return 0;}

(it is important that both BOOST_MPL_ASSERT invocations are on the same line)

On gcc 4.2.4 (Ubuntu 8.04), this leads to the following error:

$ g++ -I /src/jepler/boost_1_43_0/ main.c
main.c: In function ‘int main()’:
main.c:2: error: conflicting declaration ‘mpl_assertion_in_line_2’
main.c:2: error: ‘mpl_assertion_in_line_2’ has a previous declaration
 as ‘main()::<anonymous enum> mpl_assertion_in_line_2’

I am trying to migrate an application from boost 1_34_0 to boost 1_43_0. Among other boost features, it uses boost serialization. It has BOOST_CLASS_VERSION declarations across various header files. When two header files are included in the same source file, and they both contain BOOST_CLASS_VERSION declarations on the same source line (e.g., fooclass.h line 30 and barclass.h line 30) a similar error results.

The attached tar file demonstrates the original problem with BOOST_CLASS_VERSION that first came to my attention.

[Jeff Epler <jepler@…>]

Demonstrates the BOOST_MPL_ASSERT problem using boost serialization

[Bryce Adelstein Lelbach]

Confirmed, this is still a problem in g++-4.2, g++-4.5 and clang.