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reallocPOSIX specification:
https://pubs.opengroup.org/onlinepubs/9699919799/functions/realloc.html
Gnulib module: realloc-posix
Portability problems fixed by Gnulib:
errno to ENOMEM on
some platforms:
mingw, MSVC 14.
realloc (p, n) can succeed even if n
exceeds PTRDIFF_MAX. Although this behavior is arguably
allowed by POSIX it can lead to behavior not defined by POSIX later,
so realloc-posix does not allow going over the limit.
Without the ‘realloc-gnu’ module described below, it is not portable
to call realloc with a size of 0. With a
NULL pointer argument, this is the same ambiguity as malloc (0)
on whether a unique zero-size object is created. With a non-NULL
pointer argument p, C17 says that it is implementation-defined
whether realloc (p, 0) frees p.
Behavior varies on whether realloc (p, 0) always frees p
and successfully returns a null pointer, or always
fails and leaves p valid, or usually succeeds and returns a
unique zero-size object; a program not suspecting these variations in
semantics will leak memory (either the still-valid p, or the
non-NULL return value).
Extension: Gnulib provides a module ‘realloc-gnu’ that substitutes a
realloc implementation that behaves more like the glibc implementation.
It fixes these portability problems:
realloc (NULL, 0) returns NULL on success on some platforms:
AIX 7.2.
realloc (p, 0) with non-null p
might not free p, or might clobber errno,
or might not return NULL.