[gcc r12-7434] libstdc++: Fix -Wmaybe-uninitialized false positive [PR103984]

[gcc r12-7434] libstdc++: Fix -Wmaybe-uninitialized false positive [PR103984]

[Jonathan Wakely]

https://gcc.gnu.org/g:ad66b03b3c84786e73e73f09be19977b8f3c4ea3

commit r12-7434-gad66b03b3c84786e73e73f09be19977b8f3c4ea3
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Mar 1 09:33:21 2022 +0000

    libstdc++: Fix -Wmaybe-uninitialized false positive [PR103984]
    
    This fixes a false positive warning seen with LTO:
    
    12/bits/regex_compiler.tcc:443:32: error: '__last_char._M_char' may be used uninitialized [-Werror=maybe-uninitialized]
    
    Given that the std::regex code is not very efficient anyway, the
    overhead of initializing this byte should be minimal.
    
    libstdc++-v3/ChangeLog:
    
            PR middle-end/103984
            * include/bits/regex_compiler.h (_BracketMatcher::_M_char): Use
            default member initializer.

Diff:
---
 libstdc++-v3/include/bits/regex_compiler.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/regex_compiler.h b/libstdc++-v3/include/bits/regex_compiler.h
index 174aefe75f7..348c170c81a 100644
--- a/libstdc++-v3/include/bits/regex_compiler.h
+++ b/libstdc++-v3/include/bits/regex_compiler.h
@@ -125,7 +125,7 @@ namespace __detail
       struct _BracketState
       {
 	enum class _Type : char { _None, _Char, _Class } _M_type = _Type::_None;
-	_CharT _M_char;
+	_CharT _M_char = _CharT();
 
 	void
 	set(_CharT __c) noexcept { _M_type = _Type::_Char; _M_char = __c; }