[incubator-nuttx] branch master updated: libc/string: strcmp/strncmp cast unsigned char

[pkarashchenko]

This is an automated email from the ASF dual-hosted git repository.

pkarashchenko pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 185b1cb1b7 libc/string: strcmp/strncmp cast unsigned char
185b1cb1b7 is described below

commit 185b1cb1b78d03fccb49f5f58e159450fb3dec39
Author: Oki Minabe <minabe....@gmail.com>
AuthorDate: Sat Apr 23 16:23:25 2022 +0900

    libc/string: strcmp/strncmp cast unsigned char
    
    Summary:
    - Cast to unsigned char for strcmp and strncmp
    - strcmp and strncmp are described following by opengroup.org
    
      The sign of a non-zero return value shall be determined by the sign
      of the difference between the values of the first pair of bytes
      (both interpreted as type unsigned char) that differ in the strings
      being compared.
    
      https://pubs.opengroup.org/onlinepubs/9699919799/functions/strcmp.html
      https://pubs.opengroup.org/onlinepubs/9699919799/functions/strncmp.html
    
    Impact:
    - strcmp and strncmp return value
    
    Testing:
    - ostest on sabre-6quad:smp w/ qemu
    
    Signed-off-by: Oki Minabe <minabe....@gmail.com>
---
 libs/libc/string/lib_strcmp.c  | 9 ++++++---
 libs/libc/string/lib_strncmp.c | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/libs/libc/string/lib_strcmp.c b/libs/libc/string/lib_strcmp.c
index 2ac4f62619..edb6d23c83 100644
--- a/libs/libc/string/lib_strcmp.c
+++ b/libs/libc/string/lib_strcmp.c
@@ -34,11 +34,14 @@
 #undef strcmp /* See mm/README.txt */
 int strcmp(FAR const char *cs, FAR const char *ct)
 {
-  register signed char result;
+  register int result;
   for (; ; )
     {
-      if ((result = *cs - *ct++) != 0 || !*cs++)
-      break;
+      if ((result = (unsigned char)*cs - (unsigned char)*ct++) != 0 ||
+          !*cs++)
+        {
+          break;
+        }
     }
 
   return result;
diff --git a/libs/libc/string/lib_strncmp.c b/libs/libc/string/lib_strncmp.c
index 117f1fddf8..48e2a2486a 100644
--- a/libs/libc/string/lib_strncmp.c
+++ b/libs/libc/string/lib_strncmp.c
@@ -37,7 +37,8 @@ int strncmp(const char *cs, const char *ct, size_t nb)
   int result = 0;
   for (; nb > 0; nb--)
     {
-      if ((result = (int)*cs - (int)*ct++) != 0 || !*cs++)
+      if ((result = (unsigned char)*cs - (unsigned char)*ct++) != 0 ||
+          !*cs++)
         {
           break;
         }