As long as the stack frame is still active, the local variables are still alive and valid. So you could pass a local function as a parameter, but you could not return it. I think jwz called these "downward funargs".
GCC's nested functions are implemented with trampolines, so there will be a performance penalty. For the amount that you gain, they seem like a bad idea. Tying your code to GCC for the sake of a small amount of convenience is a bad idea.
With things like PaX the trampoline method won't work, gcc now creates thunks, which are essentially heap allocated thunks of memory (hence the name) with PROT_EXEC.
Comments
As long as the stack frame is still active, the local variables are still alive and valid. So you could pass a local function as a parameter, but you could not return it. I think jwz called these "downward funargs".
GCC supports it http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html
GCC's nested functions are implemented with trampolines, so there will be a performance penalty. For the amount that you gain, they seem like a bad idea. Tying your code to GCC for the sake of a small amount of convenience is a bad idea.
With things like PaX the trampoline method won't work, gcc now creates thunks, which are essentially heap allocated thunks of memory (hence the name) with PROT_EXEC.
The question to which I responded did not inquire about performance nor about portability
http://tirania.org/blog/archive/2011/Feb-17.html
My comment was about GCC's local functions. It wasn't really about your comment, so I regret if you took it personally.
Thank you. Much respect, sorry if I was harsh.