Comment by flohofwoe
1 year ago
The typical way to deal with this is to put the __attribute__ into a C macro which expands to nothing on compilers which don't understand GCC/Clang's __attribute__ keyword. The code without the attribute will still compile and most likely also apply the tail call optimization, you just don't get an error if the compiler can't apply the optimization.
Also TBF, hardly any real-world C code is strictly standard compliant. Many C compilers just agree on a common syntax that includes both the C standard and some popular non-standard extensions.
PS: C++ compilers actually ignore unknown attributes since the `[[attribute]]` syntax has been standardized in C++11. In GCC and Clang you'll get a warning in the standard warning set, but not in MSVC.
PPS: C23 also standardized the `[[attribute]]` syntax and also added a way to check for supported attributes:
It will compile, and eventually blow up nicely with a stack overflow OS fault.
Ah, the joys of writing "portable" C code with #ifdef spaghetti, across commercial UNIXes and their own C compilers, 20 years ago.
It only got better because for many people just like they assume Web == Chrome, C gets C == GCC, blessifully ignoring everything else.
Nowadays clang is also considered, mostly because a couple of companies wanted to replace GCC, and naturally clang needs to be able to match whatever GCC offers.
> It will compile, and eventually blow up nicely with a stack overflow OS fault.
Not at all guaranteed. Stack overflow is undefined behaviour, which means compilers can optimise your program on the assumption that it doesn’t happen.
Ah true, yet another case that one tends to forget about.
Well, if you use recursive code, you better know what you're doing. With or without tail call optimization.
Loops are just a special, limited case of recursion.
(And only necessary in languages that have trouble implementing function calls properly.)