Symbol-Renaming Pragmas (Using the GNU Compiler Collection (GCC))

#### 6.5.9 Symbol-Renaming Pragmas ¶

GCC supports a `#pragma` directive that changes the name used in assembly for a given declaration. While this pragma is supported on all platforms, it is intended primarily to provide compatibility with the Solaris system headers. This effect can also be achieved using the asm labels extension (see Controlling Names Used in Assembler Code).

`redefine_extname oldname newname` ¶

  This pragma gives the C function oldname the assembly symbol newname. The preprocessor macro `__PRAGMA_REDEFINE_EXTNAME` is defined if this pragma is available (currently on all platforms).

This pragma and the `asm` labels extension interact in a complicated manner. Here are some corner cases you may want to be aware of:

1. This pragma silently applies only to declarations with external linkage. The `asm` label feature does not have this restriction.
2. In C++, this pragma silently applies only to declarations with “C” linkage. Again, `asm` labels do not have this restriction.
3. If either of the ways of changing the assembly name of a declaration are 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.
4. The oldname used by `#pragma redefine_extname` is always the C-language name.