Clang does not support gcc-style nested functions

[rnk]

Bugzilla Link	9206
Resolution	WONTFIX
Resolved on	Jul 12, 2011 09:11
Version	trunk
OS	Linux

Extended Description

Here are the gcc docs for this gnu-tension:
http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html

Is this worth supporting in clang and LLVM? My understanding of the implementation is that you emit snippet of code to the stack which loads the address of the parent stack frame and jumps into the nested function.

It seems LLVM already supports trampolines, so this would mostly be frontend work.
http://llvm.org/docs/LangRef.html#int_it

[lattner]

Hi Reid,

This is one feature that we really do not want to implement. Besides adding a bunch of complexity, among other things this makes parser error recovery worse: you don't know if you're entering a nested function or if a missing } happened.

[llvmbot]

Is there any chance a simple version of nested functions gets implemented anytime soon (ie. without access to parent function variables / labels)?
They are very handy when implementing complex type-aware macros.