From: Jonathan Wakely <jwakely@redhat.com>
Date: Thu, 5 Feb 2026 17:32:23 +0000 (+0000)
Subject: libstdc++: Fix std::regex_traits::lookup_classname [PR124015]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49d219a5d7a8ad570992a4065268b58a581b7d9f;p=thirdparty%2Fgcc.git

libstdc++: Fix std::regex_traits::lookup_classname [PR124015]

This fixes a bug in regex_traits::lookup_classname(f, l, true) where the
result was always ctype_base::alpha for any input sequence [f, l) that
has the ctype_base::lower or ctype_base::upper bits set. For targets
that define alpha as lower|upper (rather than having a distinct bit for
alpha) this bug meant that all masks which have lower or upper bits set
were replaced with alpha when the icase parameter is true. This has the
effect that trying to do a case insensitive match for [:alnum:],
[:graph:], or [:print:] was equivalent to matching [:alpha:] instead,
which is obviously not correct.

Based on inspection of the ctype_base.h files under the config/os
directory, the bug appears to affect newlib, picolibc, qnx and vxworks.

libstdc++-v3/ChangeLog:

	PR libstdc++/124015
	* include/bits/regex.tcc (regex_traits::lookup_classname): Fix
	handling of icase parameter.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
---

diff --git a/libstdc++-v3/include/bits/regex.tcc b/libstdc++-v3/include/bits/regex.tcc
index ca500d21c34..7715d653df5 100644
--- a/libstdc++-v3/include/bits/regex.tcc
+++ b/libstdc++-v3/include/bits/regex.tcc
@@ -302,8 +302,8 @@ namespace __detail
 	if (__s == __it.first)
 	  {
 	    if (__icase
-		&& ((__it.second
-		     & (ctype_base::lower | ctype_base::upper)) != 0))
+		&& (__it.second._M_base == ctype_base::lower
+		      || __it.second._M_base == ctype_base::upper))
 	      return ctype_base::alpha;
 	    return __it.second;
 	  }