On its own, -std=c11 hides POSIX and other extensions from C headers such as <stdlib.h> when building against glibc. This causes the posix_memalign probe to fail incorrectly with compilers that do not accept implicit function declarations. _DEFAULT_SOURCE is ignored by most non-GNU/Linux systems or not relevant in this context, so there is no separate check for adding it.
On its own,
-std=c11hides POSIX and other extensions from C headers such as<stdlib.h>when building against glibc. This causes theposix_memalignprobe to fail incorrectly with compilers that do not accept implicit function declarations._DEFAULT_SOURCEis ignored by most non-GNU/Linux systems or not relevant in this context, so there is no separate check for adding it.Related to: