* lib/realloc.c (rpl_realloc): Simplify and tune by using
HAVE_REALLOC_0_NONNULL and HAVE_MALLOC_PTRDIFF, and
by having just one call to realloc instead of two.
* lib/reallocarray.c (reallocarray): Simplify and tune
by delegating the zero case to the revised realloc.
* m4/eealloc.m4 (_AC_FUNC_REALLOC_IF): Since only eealloc uses
this macro now, move its definition here ...
* m4/realloc.m4: ... from here.
(gl_FUNC_REALLOC_0_NONNULL): Also check that realloc (p, 0)
returns nonnull. Require gl_FUNC_REALLOC_POSIX.
Define HAVE_REALLOC_0_NONNULL.
* m4/reallocarray.m4 (gl_FUNC_REALLOCARRAY):
Also replace reallocarray if it returns a null pointer for size zero.
* modules/eealloc (Files): Remove m4/realloc.m4.
* modules/realloc-posix (Depends-on): Add extensions-aix.
* modules/reallocarray (Files): Add m4/realloc.m4.
* doc/Makefile (undocumented-modules.texi): New rule.
(%.info, %.html, %.dvi, %.pdf): Depend on undocumented-modules.texi.
(mostlyclean): Remove also *.m and *.tmp.
(force): New rule.
* doc/*.texi: Add module index entries.
* doc/*/*.texi: Likewise.
* doc/posix-functions/malloc.texi: AIX is sans _LINUX_SOURCE_COMPAT.
* doc/posix-functions/realloc.texi:
Give more details about what recent POSIX versions say,
and fix some misperceptions about C89 through C11.
Document that the GNU behavior does not conform to POSIX,
and that AIX's behavior with _LINUX_SOURCE_COMPAT
matches glibc's circa 1999 behavior, not its current behavior.
Be a little less confident about realloc-gnu, since it doesn't
fully implement current glibc behavior.
Give more details about when memory leaks or false positives can occur.
* doc/posix-functions/reallocarray.texi:
Say that it shares realloc’s woes with zero sizes.
