Commit b0975710 authored by Peter Rosin's avatar Peter Rosin Committed by Linus Torvalds

lib/string.c: allow searching for NUL with strnchr

Patch series "lib/string: search for NUL with strchr/strnchr".

I noticed an inconsistency where strchr and strnchr do not behave the
same with respect to the trailing NUL.  strchr is standardised and the
kernel function conforms, and the kernel relies on the behavior.  So,
naturally strchr stays as-is and strnchr is what I change.

While writing a few tests to verify that my new strnchr loop was sane, I
noticed that the tests for memset16/32/64 had a problem.  Since it's all
about the lib/string.c file I made a short series of it all...

This patch (of 3):

strchr considers the terminating NUL to be part of the string, and NUL
can thus be searched for with that function.  For consistency, do the
same with strnchr.

Link: http://lkml.kernel.org/r/20190506124634.6807-2-peda@axentia.seSigned-off-by: default avatarPeter Rosin <peda@axentia.se>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4c6080cd
...@@ -400,6 +400,9 @@ EXPORT_SYMBOL(strncmp); ...@@ -400,6 +400,9 @@ EXPORT_SYMBOL(strncmp);
* strchr - Find the first occurrence of a character in a string * strchr - Find the first occurrence of a character in a string
* @s: The string to be searched * @s: The string to be searched
* @c: The character to search for * @c: The character to search for
*
* Note that the %NUL-terminator is considered part of the string, and can
* be searched for.
*/ */
char *strchr(const char *s, int c) char *strchr(const char *s, int c)
{ {
...@@ -453,12 +456,18 @@ EXPORT_SYMBOL(strrchr); ...@@ -453,12 +456,18 @@ EXPORT_SYMBOL(strrchr);
* @s: The string to be searched * @s: The string to be searched
* @count: The number of characters to be searched * @count: The number of characters to be searched
* @c: The character to search for * @c: The character to search for
*
* Note that the %NUL-terminator is considered part of the string, and can
* be searched for.
*/ */
char *strnchr(const char *s, size_t count, int c) char *strnchr(const char *s, size_t count, int c)
{ {
for (; count-- && *s != '\0'; ++s) while (count--) {
if (*s == (char)c) if (*s == (char)c)
return (char *)s; return (char *)s;
if (*s++ == '\0')
break;
}
return NULL; return NULL;
} }
EXPORT_SYMBOL(strnchr); EXPORT_SYMBOL(strnchr);
......
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