https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110861
Bug ID: 110861
Summary: Bad codegen leading to runtime segfault when mixing
import and #include
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: headch at gmail dot com
Target Milestone: ---
$ g++-13 --version
g++-13 (Gentoo 13.2.0 p3) 13.2.0
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ cat hello.cpp
#include <string_view>
import <iostream>;
void f(std::string_view sv) {
std::cout << sv;
}
int main() {
f("hello\n");
}
$ g++-13 -O1 -Wall -Wextra -c -std=c++20 -x c++-system-header -fmodules-ts
-fmodule-header=system iostream
$ g++-13 -std=c++20 -O1 -Wall -Wextra -fmodules-ts -ohello hello.cpp
In file included from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/bits/basic_string.h:47,
from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/string:54,
from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/bits/locale_classes.h:40,
from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/bits/ios_base.h:41,
from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/ios:44,
from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/ostream:40,
from
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/iostream:41,
of module /usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/iostream,
imported at hello.cpp:2:
In member function ‘constexpr const std::basic_string_view<_CharT,
_Traits>::value_type* std::basic_string_view<_CharT, _Traits>::data() const
[with _CharT = char; _Traits = std::char_traits<char>]’,
inlined from ‘std::basic_ostream<_CharT, _Traits>&
std::operator<<(basic_ostream<_CharT, _Traits>&, basic_string_view<_CharT,
_Traits>) [with _CharT = char; _Traits = char_traits<char>]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/string_view:762:30,
inlined from ‘void f(std::string_view)’ at hello.cpp:5:15:
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/string_view:292:22:
warning: ‘this’ is used uninitialized [-Wuninitialized]
292 | { return this->_M_str; }
| ^~~~~~
In file included from hello.cpp:1:
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/string_view: In function
‘void f(std::string_view)’:
/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13/string_view:760:5: note:
‘this’ was declared here
760 | operator<<(basic_ostream<_CharT, _Traits>& __os,
| ^~~~~~~~
$ ./hello
Segmentation fault (core dumped)
If I use optimization level zero, the problem goes away (both the segfault and
the “uninitialized” warning). Likewise if I import both headers rather than
including one of them. But as far as I’m aware, I haven’t found any indication
that the stdlib is required to be either all-included or all-imported and not a
mix.
