string/strcmp.c

   1 /* Copyright (C) 1991-2019 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19
  20 #undef strcmp
  21
  22 #ifndef STRCMP
  23 # define STRCMP strcmp
  24 #endif
  25
  26 /* Compare S1 and S2, returning less than, equal to or
  27    greater than zero if S1 is lexicographically less than,
  28    equal to or greater than S2.  */
  29 int
  30 STRCMP (const char *p1, const char *p2)
  31 {
  32   const unsigned char *s1 = (const unsigned char *) p1;
  33   const unsigned char *s2 = (const unsigned char *) p2;
  34   unsigned char c1, c2;
  35
  36   do
  37     {
  38       c1 = (unsigned char) *s1++;
  39       c2 = (unsigned char) *s2++;
  40       if (c1 == '\0')
  41         return c1 - c2;
  42     }
  43   while (c1 == c2);
  44
  45   return c1 - c2;
  46 }
  47 libc_hidden_builtin_def (strcmp)