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argp: Don't rely on undefined behaviour of _tolower().

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Patch by Eric Blake
<https://lists.gnu.org/archive/html/bug-gnulib/2009-09/msg00287.html>.

* argp/argp-help.c (hol_entry_cmp): Don't use _tolower on values that are
not upper-case.  Pass correct range to tolower.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Bruno Haible 2021-01-07 02:06:17 +01:00 committed by Adhemerval Zanella
parent 5ec029c883
commit 1b3fc33f81
1 changed files with 4 additions and 6 deletions
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10
argp/argp-help.c
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@ -780,13 +780,11 @@ hol_entry_cmp (const struct hol_entry *entry1,
first, but as they're not displayed, it doesn't matter where
they are. */
{
char first1 = short1 ? short1 : long1 ? *long1 : 0;
char first2 = short2 ? short2 : long2 ? *long2 : 0;
#ifdef _tolower
int lower_cmp = _tolower (first1) - _tolower (first2);
#else
unsigned char first1 = short1 ? short1 : long1 ? *long1 : 0;
unsigned char first2 = short2 ? short2 : long2 ? *long2 : 0;
/* Use tolower, not _tolower, since the latter has undefined
behaviour for characters that are not uppercase letters. */
int lower_cmp = tolower (first1) - tolower (first2);
#endif
/* Compare ignoring case, except when the options are both the
same letter, in which case lower-case always comes first. */
return lower_cmp ? lower_cmp : first2 - first1;