From 969abd302211262562df93ae5412ee319aae69e6 Mon Sep 17 00:00:00 2001 From: Werner Koch Date: Tue, 3 Mar 2020 15:41:39 +0100 Subject: core: New function gpgrt_reallocarray. * src/init.c (_gpgrt_reallocarray): New. * src/visibility.c (gpgrt_reallocarray): New. * src/gpg-error.vers, src/gpg-error.def.in: Add new function. * src/gpg-error.h.in: Add new interface. * tests/t-malloc.c: New. * tests/Makefile.am (TESTS): Add new test. -- Note that this function is different from the glibc function because it has an extra parameter which allows to clear the new elements. A realloc after a calloc with forgotten memset after it is a common source of error, thus we introduce this slightly different function. Signed-off-by: Werner Koch --- src/init.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) (limited to 'src/init.c') diff --git a/src/init.c b/src/init.c index 8ddf0c0..6239682 100644 --- a/src/init.c +++ b/src/init.c @@ -259,6 +259,55 @@ _gpgrt_realloc (void *a, size_t n) } +/* This is safe version of realloc useful for reallocing a calloced + * array. There are two ways to call it: The first example + * reallocates the array A to N elements each of SIZE but does not + * clear the newly allocated elements: + * + * p = gpgrt_reallocarray (a, n, n, nsize); + * + * Note that when NOLD is larger than N no cleaning is needed anyway. + * The second example reallocates an array of size NOLD to N elements + * each of SIZE but clear the newly allocated elements: + * + * p = gpgrt_reallocarray (a, nold, n, nsize); + * + * Note that gpgrt_reallocarray (NULL, 0, n, nsize) is equivalent to + * _gpgrt_calloc (n, nsize). + * + */ +void * +_gpgrt_reallocarray (void *a, size_t oldnmemb, size_t nmemb, size_t size) +{ + size_t oldbytes, bytes; + char *p; + + bytes = nmemb * size; /* size_t is unsigned so the behavior on overflow + * is defined. */ + if (size && bytes / size != nmemb) + { + _gpg_err_set_errno (ENOMEM); + return NULL; + } + + p = _gpgrt_realloc (a, bytes); + if (p && oldnmemb < nmemb) + { + /* OLDNMEMBS is lower than NMEMB thus the user asked for a + calloc. Clear all newly allocated members. */ + oldbytes = oldnmemb * size; + if (size && oldbytes / size != oldnmemb) + { + xfree (p); + _gpg_err_set_errno (ENOMEM); + return NULL; + } + memset (p + oldbytes, 0, bytes - oldbytes); + } + return p; +} + + /* The malloc to be used for data returned by the public API. */ void * _gpgrt_malloc (size_t n) -- cgit v1.2.3