| Function Names as Strings

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GCC predefines two magic identifiers to hold the name of the current function. The identifier `__FUNCTION__` holds the name of the function as it appears in the source. The identifier `__PRETTY_FUNCTION__` holds the name of the function pretty printed in a language specific fashion. (These names are always the same in a C function, but in a C++ function they may be different; don't care about this, because TIGCC is not a C++ compiler.)
The compiler automatically replaces the identifiers with a string literal containing the appropriate name. Thus, they are neither preprocessor macros, like `__FILE__` and `__LINE__`, nor variables. This means that they catenate with other string literals, and that they can be used to initialize char arrays. For example

    char here[] = "Function " __FUNCTION__ " in " __FILE__;

On the other hand, `#ifdef __FUNCTION__` does not have any special meaning inside a function, since the preprocessor does not do anything special with the identifier `__FUNCTION__`.
Note that these semantics are deprecated, and that GCC 3.2 will handle `__FUNCTION__` and `__PRETTY_FUNCTION__` the same way as `__func__`. `__func__` is defined by the ISO standard C99:
The identifier `__func__` is implicitly declared by the translator as if, immediately following the opening brace of each function definition, the declaration

    static const char __func__[] = "function-name";

appeared, where function-name is the name of the lexically-enclosing function. This name is the unadorned name of the function.
By this definition, `__func__` is a variable, not a string literal. In particular, `__func__` does not catenate with other string literals.