GCC has nested functions, which most GCC users hate. Clang has blocks, which are at least widely used on OS X at least and proposed for standardization. I'm not sure this is a point in GCC's favor.

As an Objective-C (iOS) developer, I really love blocks. I thought the syntax was kind of weird when starting to learn it, but it's grown on me. I really hope ObjC blocks will become part of the C standard someday. If I remember people have proposed C++ lambdas to become part of the C standard as well. It will be interesting to see which one (if any) will win in a standardising process.

More info on ObjC blocks vs C++ lambdas in this blog posting: http://www.mikeash.com/pyblog/friday-qa-2011-06-03-objective...

Is that C language features or compiler-specific extensions? Arguably, sticking to the standard is actually the better alternative here in terms of portability.

You're right - it's a compiler extension to a language (apparently) called "GNU C"[1]: http://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html

Seems like a very nice feature though.

[1]: First time I've heard this term. I'm not sure how I feel about it.

You can usually use "-std=c99" to ban features of concern.

Clang has blocks, which, while different, are at least an arguably superior replacement for gcc's nested functions.