Long term, gcc extensions mean a given piece of code will only be compilable by gcc. If the extension is succesful enough, it may even be adopted by other compilers, such as Intel CC. Happened in the past.
Personally, I tend to not like gcc extensions. Especially the silent variety. Now that the C language is reasonably normalized, staying away from extensions is a good idea. Or knowing what you do. There are *tons* of clueless people out there writing code... clueless when it comes to portability, because they might be geniuses in their own domain. For instance, I just stumbled on the following FAQ entry: Q. On RedHat Linux 7.* I got the following error on compilation of toolkit: [...] ../lib/libncbi.a(ncbifile.o): In function `Nlm_TmpNam': ncbifile.o(.text+0x728): the use of `tempnam' is dangerous, better use `mkstemp' collect2: ld returned 1 exit status make: *** [Psequin] Error 1 FAILURE primary make status = 0, demo = 0, threaded_demo = 0, net = 2 A. The problem is that you probably have the 'openmotif-devel' RPM installed, which provides a 'libXm.a' that defines that function. We don't build the toolkit aganist Open Motif, we build it against Lesstif. If the end-user removes the 'openmotif-devel' package, things should work. (The user might have to install a lesstif package or two, depending on what they've already got set up.) Why RedHat lets you install two different Motif toolkits at the same time, when they don't have identical implementations, is beyond us. priceless, isn't it ? and the build system the people behind blast have developed is shockingly different too (csh scripting anyone ?) Well, the more non-standard stuff there is that isn't obviously non-standard, the more `fun' issues along these lines we'll get... I spend enough time already, when I wear my OpenBSD porter cap, porting linux-only, i386-centric stuff that depends on gcc, gnu-make, bash stuff and still claims to be Unix (#include <values.h>, yeah right... %.o: %.c, yeah right too) Personally, I would even say that it would be *great* if gcc would start warning if you use any extension, unless you explicitly disable those warnings... (except for __extension__ in header files, and then I've stumbled upon situations where it hurts still).
