What's the Difference Between `__PRETTY_FUNCTION__`, `__FUNCTION__`, and `__func__`?

Understanding the Differences: PRETTY_FUNCTION__, __FUNCTION__, and __func

In programming, accessing information about the current function can be useful for debugging, logging, and other purposes. Three commonly used identifiers in C and C serve this function: __PRETTY_FUNCTION__, __FUNCTION__, and __func__. Each one holds its own unique characteristics worth understanding.

__func__: A Standard Identifier from C99

Defined in C99, func is an implicitly declared identifier that expands to a character array containing the name of the function in which it is used. As a declared identifier, func behaves differently than a preprocessor macro.

__FUNCTION__: A Pre-Standard Extension

Widely supported by C compilers like gcc and Visual C , FUNCTION is not strictly a part of the C standard. It typically behaves similarly to __func__, but some inconsistencies between compilers may exist.

__PRETTY_FUNCTION__: A GCC Extension

PRETTY_FUNCTION is a gcc-specific extension that is comparable to __FUNCTION__. However, for C functions, it returns the "pretty" name, which includes the function's signature.

Choosing the Right Identifier

Selecting which identifier to use primarily depends on support and functionality requirements:

• If standard C99 compliance is necessary, use __func__.
• If you require a more portable option with behavior similar to __func__, consider using __FUNCTION__.
• If your code is specifically designed for gcc and you want the "pretty" function name, employ __PRETTY_FUNCTION__.

It's also important to consult specific compiler documentation for nonstandard extensions like FUNCTION and __PRETTY_FUNCTION__. For example, Visual C offers similar extensions like __FUNCSIG__.

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