reallocarray(3) looks nifty, but until it's available on a wider, ideally more standard-driven basis than just OpenBSD and FreeBSD, it's likely to not see wide uptake.
Many open source projects include their own, or simply bundle the OpenBSD implementation:
* mandoc
* flex
* unbound and nsd
* tor
* tmux
* libbsd
* libressl
* xorg-xserver
* ...reallocarray() has some difficulties as an interface, mostly inherited from realloc(). I'm a bigger fan of reallocarr(), but that's NetBSD only. We (the operating systems community) need to find a consensus here, but I'm not convinced that reallocarray() is that consensus yet.
reallocarr changes the semantics. Equally easy in new pieces of code and a little harder when converting existing code.
#define MUL_NO_OVERFLOW ((size_t)1 << (sizeof(size_t) * 4))
void *reallocarray(void *optr, size_t nmemb, size_t size) {
if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
nmemb > 0 && SIZE_MAX / nmemb < size) {
errno = ENOMEM;
return NULL;
}
return realloc(optr, size * nmemb);
}