lib/realloc.c

   1 /* realloc() function that is glibc compatible.
   2
   3    Copyright (C) 1997, 2003-2004, 2006-2007, 2009-2024 Free Software
   4    Foundation, Inc.
   5
   6    This file is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU Lesser General Public License as
   8    published by the Free Software Foundation; either version 2.1 of the
   9    License, or (at your option) any later version.
  10
  11    This file is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 /* written by Jim Meyering and Bruno Haible */
  20
  21 /* Ensure that we call the system's realloc() below.  */
  22 #define _GL_USE_STDLIB_ALLOC 1
  23 #include <config.h>
  24
  25 #define _GL_REALLOC_INLINE _GL_EXTERN_INLINE
  26 #include <stdlib.h>
  27
  28 #include <errno.h>
  29 #include <stdckdint.h>
  30
  31 #ifdef __CHERI_PURE_CAPABILITY__
  32 # include <cheri.h>
  33 #endif
  34
  35 #ifndef _GL_INLINE_RPL_REALLOC
  36
  37 /* Change the size of an allocated block of memory P to N bytes,
  38    with error checking.  If P is NULL, use malloc.  Otherwise if N is zero,
  39    free P and return NULL.  */
  40
  41 void *
  42 rpl_realloc (void *p, size_t n)
  43 {
  44   size_t n1 = n;
  45
  46   if (n == 0)
  47     {
  48 # if NEED_SANITIZED_REALLOC
  49       /* When P is non-null, ISO C23 §7.24.3.7.(3) says realloc (P, 0) has
  50          undefined behavior even though C17 and earlier partially defined
  51          the behavior.  Let the programmer know.
  52          When the undefined-behaviour sanitizers report this case, i.e. when
  53          <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117233> and
  54          <https://github.com/llvm/llvm-project/issues/113065>
  55          have been closed and new releases of GCC and clang have been made,
  56          we can revisit this code.  */
  57       if (p != NULL)
  58         abort ();
  59 # endif
  60
  61       /* realloc (NULL, 0) acts like glibc malloc (0), i.e., like malloc (1)
  62          except the caller cannot dereference any non-null return.
  63
  64          realloc (P, 0) with non-null P is a messier situation.
  65          As mentioned above, C23 says behavior is undefined.
  66          POSIX.1-2024 extends C17 to say realloc (P, 0)
  67          either fails by setting errno and returning a null pointer,
  68          or succeeds by freeing P and then either:
  69            (a) setting errno=EINVAL and returning a null pointer; or
  70            (b) acting like a successful malloc (0).
  71          glibc 1 through 2.1 realloc acted like (b),
  72          which conforms to C17, to C23 and to POSIX.1-2024.
  73          glibc 2.1.1+ realloc acts like (a) except it does not set errno;
  74          this conforms to C17 and to C23 but not to POSIX.1-2024.
  75          Quite possibly future versions of POSIX will change,
  76          due either to C23 or to (a)'s semantics being messy.
  77          Act like (b), as that's easy, matches GNU, BSD and V7 malloc,
  78          matches BSD and V7 realloc, and requires no extra code at
  79          caller sites.  */
  80
  81 # if !HAVE_REALLOC_0_NONNULL
  82       n1 = 1;
  83 # endif
  84     }
  85
  86 # if !HAVE_MALLOC_PTRDIFF
  87   ptrdiff_t signed_n;
  88   if (ckd_add (&signed_n, n, 0))
  89     {
  90       errno = ENOMEM;
  91       return NULL;
  92     }
  93 # endif
  94
  95   void *result = realloc (p, n1);
  96
  97 # if !HAVE_MALLOC_POSIX
  98   if (result == NULL)
  99     errno = ENOMEM;
 100 # endif
 101
 102 # ifdef __CHERI_PURE_CAPABILITY__
 103   if (result != NULL)
 104     result = cheri_bounds_set (result, n);
 105 # endif
 106
 107   return result;
 108 }
 109
 110 #endif