5.52.6 Symbol-Renaming Pragmas
For compatibility with the Solaris and Tru64 UNIX system headers, GCC
#pragma directives which change the name used in
assembly for a given declaration. These pragmas are only available on
platforms whose system headers need them. To get this effect on all
platforms supported by GCC, use the asm labels extension (see Asm Labels).
This pragma gives the C function oldname the assembly symbol
newname. The preprocessor macro
__PRAGMA_REDEFINE_EXTNAMEwill be defined if this pragma is available (currently only on Solaris).
This pragma causes all subsequent external function and variable
declarations to have string prepended to their assembly symbols.
This effect may be terminated with another
extern_prefixpragma whose argument is an empty string. The preprocessor macro
__PRAGMA_EXTERN_PREFIXwill be defined if this pragma is available (currently only on Tru64 UNIX).
These pragmas and the asm labels extension interact in a complicated manner. Here are some corner cases you may want to be aware of.
- Both pragmas silently apply only to declarations with external linkage. Asm labels do not have this restriction.
- In C++, both pragmas silently apply only to declarations with “C” linkage. Again, asm labels do not have this restriction.
- If any of the three ways of changing the assembly name of a declaration is applied to a declaration whose assembly name has already been determined (either by a previous use of one of these features, or because the compiler needed the assembly name in order to generate code), and the new name is different, a warning issues and the name does not change.
- The oldname used by
#pragma redefine_extnameis always the C-language name.
#pragma extern_prefixis in effect, and a declaration occurs with an asm label attached, the prefix is silently ignored for that declaration.
#pragma redefine_extnameapply to the same declaration, whichever triggered first wins, and a warning issues if they contradict each other. (We would like to have
#pragma redefine_extnamealways win, for consistency with asm labels, but if
#pragma extern_prefixtriggers first we have no way of knowing that that happened.)