The offsetof() macro defined in stddef.h evaluates to code that can violate the C++ standard depending upon the context of its use. I have attached code that demonstrates the problem. GCC 3.4.2 in the base system refuses to compile the code, giving this error message: % g++ -c const-exp.cpp const-exp.cpp:14: error: a casts to a type other than an integral or enumeration type cannot appear in a constant-expression const-exp.cpp:14: error: '->' cannot appear in a constant-expression const-exp.cpp:14: error: `&' cannot appear in a constant-expression The gcc34 port (gcc-3.4.2_20040827) builds it just fine. The difference, as far as I can tell, is that gcc34 from the Ports Collection gets offsetof() from its own stddef.h, which has C++-friendly code: /* Offset of member MEMBER in a struct of type TYPE. */ #ifndef __cplusplus #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) #else /* The cast to "char &" below avoids problems with user-defined "operator &", which can appear in a POD type. */ #define offsetof(TYPE, MEMBER) \ (__offsetof__ (reinterpret_cast <size_t> \ (&reinterpret_cast <const volatile char &> \ (static_cast<TYPE *> (0)->MEMBER)))) #endif /* C++ */ Would fixing this problem be as simple as using the above code in /usr/include/stddef.h? The attached code was adapted from some very similar code in Boost.Python (from the file boost/python/object/instance.hpp), which does not compile with the base system GCC 3.4.2. There may be other parts of Boost 1.31.0--and the upcoming Boost 1.32.0--that are affected by this offsetof() problem. -Patrick -- Patrick L. Hartling | Research Assistant, VRAC http://www.137.org/patrick/ | 2274 Howe Hall Room 2624 PGP: http://tinyurl.com/2oum9 | http://www.vrac.iastate.edu/
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