[PATCH v4 2/3] posix: regcomp(): clear RE_DOT_NOT_NULL

[наб <nabijaczleweli@nabijaczleweli.xyz>]

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The POSIX API always stops at first NUL so there's no change for that.

The BSD REG_STARTEND API, with its explicit range, can include NULs
within that range, and those NULs are matched with . and [^].

Heretofor, for a string of "a\0c", glibc would match "[^q]c", but not
".c". This is both inconsistent and nonconformant to BSD REG_STARTEND.

With this patch, they're identical like you'd expect, and the
  tst-reg-startend.c: ..c: a^@c: no match$
failure is removed.

Another approach would be to remove it from _RE_SYNTAX_POSIX_COMMON,
but it's unclear to me what the custody chain is like for that and what
other regex APIs glibc offers that could be affected by this.

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
 posix/regcomp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/posix/regcomp.c b/posix/regcomp.c
index 12650714c0..a928ef6c2d 100644
--- a/posix/regcomp.c
+++ b/posix/regcomp.c
@@ -462,7 +462,7 @@ regcomp (regex_t *__restrict preg, const char *__restrict pattern, int cflags)
 {
   reg_errcode_t ret;
   reg_syntax_t syntax = ((cflags & REG_EXTENDED) ? RE_SYNTAX_POSIX_EXTENDED
-			 : RE_SYNTAX_POSIX_BASIC);
+			 : RE_SYNTAX_POSIX_BASIC) & ~RE_DOT_NOT_NULL;
 
   preg->buffer = NULL;
   preg->allocated = 0;
-- 
2.30.2


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