5.47.5 Symbol-Renaming Pragmas
For compatibility with the Solaris and Tru64 UNIX system headers, GCC
supports two #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).
redefine_extname oldname newname-
This pragma gives the C function oldname the assembly symbol
newname. The preprocessor macro
__PRAGMA_REDEFINE_EXTNAME
will be defined if this pragma is available (currently only on
Solaris).
extern_prefix string-
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_prefix pragma
whose argument is an empty string. The preprocessor macro
__PRAGMA_EXTERN_PREFIX will 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_extname is
always the C-language name.
- If
#pragma extern_prefix is in effect, and a declaration
occurs with an asm label attached, the prefix is silently ignored for
that declaration.
- If
#pragma extern_prefix and #pragma redefine_extname
apply to the same declaration, whichever triggered first wins, and a
warning issues if they contradict each other. (We would like to have
#pragma redefine_extname always win, for consistency with asm
labels, but if #pragma extern_prefix triggers first we have no
way of knowing that that happened.)
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