https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105423
Bug ID: 105423
Summary: Bogus -Werror=maybe-uninitialized with definitely
initialized variable
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: byteslice at airmail dot cc
Target Milestone: ---
Created attachment 52896
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52896&action=edit
Cvised example
On gcc 12.0.1 20220413 (Fedora 36 Beta), with c++ -O1
-Werror=maybe-uninitialized, the attachment fails to compile, with the
following message:
In member function 'void std::Trans_NS___cxx11_basic_string<_CharT,
<template-parameter-1-2>, <template-parameter-1-3> >::_S_copy(_CharT*) [with
_CharT = char; _Traits = std::char_traits; <template-parameter-1-3> = char]',
inlined from 'constexpr std::Trans_NS___cxx11_basic_string<_CharT, _Traits,
_Alloc>& std::Trans_NS___cxx11_basic_string<_CharT, <template-parameter-1-2>,
<template-parameter-1-3> >::_M_replace(const _CharT*, long int) [with _CharT =
char; _Traits = std::char_traits; <template-parameter-1-3> = char]' at
<source>:49:12,
inlined from 'void std::Trans_NS___cxx11_basic_string<_CharT,
<template-parameter-1-2>, <template-parameter-1-3> >::operator=(const _CharT*)
[with _CharT = char; _Traits = std::char_traits; <template-parameter-1-3> =
char]' at <source>:40:15,
inlined from 'void Shuffle()' at <source>:55:8:
<source>:36:46: error: '((char*)((char*)&mask +
offsetof(std::Trans_NS___cxx11_basic_string<char, std::char_traits,
char>,std::Trans_NS___cxx11_basic_string<char, std::char_traits,
char>::<unnamed>)))[2]' may be used uninitialized [-Werror=maybe-uninitialized]
36 | void _S_copy(_CharT *__s) { _Traits::assign(_S_copy___d, *__s); }
| ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
<source>: In function 'void Shuffle()':
<source>:54:44: note: 'mask' declared here
54 | std::Trans_NS___cxx11_basic_string<char> mask{};
| ^~~~
In member function 'void std::Trans_NS___cxx11_basic_string<_CharT,
<template-parameter-1-2>, <template-parameter-1-3> >::_S_copy(_CharT*) [with
_CharT = char; _Traits = std::char_traits; <template-parameter-1-3> = char]',
inlined from 'constexpr std::Trans_NS___cxx11_basic_string<_CharT, _Traits,
_Alloc>& std::Trans_NS___cxx11_basic_string<_CharT, <template-parameter-1-2>,
<template-parameter-1-3> >::_M_replace(const _CharT*, long int) [with _CharT =
char; _Traits = std::char_traits; <template-parameter-1-3> = char]' at
<source>:49:12,
inlined from 'void std::Trans_NS___cxx11_basic_string<_CharT,
<template-parameter-1-2>, <template-parameter-1-3> >::operator=(const _CharT*)
[with _CharT = char; _Traits = std::char_traits; <template-parameter-1-3> =
char]' at <source>:40:15,
inlined from 'void Shuffle()' at <source>:55:8:
<source>:36:47: error:
'mask.std::Trans_NS___cxx11_basic_string<char>::_S_copy___d' may be used
uninitialized [-Werror=maybe-uninitialized]
36 | void _S_copy(_CharT *__s) { _Traits::assign(_S_copy___d, *__s); }
| ^~~~~~~~~~~
<source>: In function 'void Shuffle()':
<source>:54:44: note: 'mask' declared here
54 | std::Trans_NS___cxx11_basic_string<char> mask{};
| ^~~~
cc1plus: some warnings being treated as errors
Compiler returned: 1
This warning is bogus because the variable mask is default brace-initialized
and thus its member _S_copy___d is also initialized. The bogus warning does not
appear in older versions of GCC.
Adding -fno-inline to options allows compilation to succeed.
