[llvm-bugs] [Bug 32387] New: string::size() use of uninitialized memory (MSan)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=32387

            Bug ID: 32387
           Summary: string::size() use of uninitialized memory (MSan)
           Product: libc++
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: All Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: gonzalobg88 at gmail.com
                CC: llvm-bugs at lists.llvm.org, mclow.lists at gmail.com

The following MWE produces a MemorySanitizer error:

MWE:

#include <vector>
#include <string>

int main() 
{
    auto vec = std::vector<std::string>{{"a"}, {"b"}, {"c"}};
    auto it = std::find(std::begin(vec), std::end(vec), "b");
    assert(it2 == vec.begin() + 1);
}

Error:

==25671==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x49a8ca in std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::size() const
/home/gonzalo/pool/msan/include/c++/v1/string:894:17
    #1 0x49a8ca in bool std::__1::operator==<char, std::__1::char_traits<char>,
std::__1::allocator<char> >(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*)
/home/gonzalo/pool/msan/include/c++/v1/string:3581
    #2 0x49a8ca in std::__1::__wrap_iter<std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >*>
std::__1::find<std::__1::__wrap_iter<std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >*>, char
[2]>(std::__1::__wrap_iter<std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >*>,
std::__1::__wrap_iter<std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >*>, char const (&) [2])
/home/gonzalo/pool/msan/include/c++/v1/algorithm:891
    #3 0x49a8ca in main test.cpp:7
    #4 0x7f220bb66b04 in __libc_start_main (/lib64/libc.so.6+0x21b04)
    #5 0x42384e in _start
/home/abuild/rpmbuild/BUILD/glibc-2.19/csu/../sysdeps/x86_64/start.S:122

SUMMARY: MemorySanitizer: use-of-uninitialized-value
/home/gonzalo/pool/msan/include/c++/v1/string:894:17 in
std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::size() const
Exiting

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