Why valgrind reporting errors for libstdc ++ std :: locale?

Related question: wifstream with imbue, locale produces valgrind errors

I am using cppreference examples (potentially buggy), in particular the ones provided on the page imbue

. Using the command line in coliru online compiler :

clang++ -std=c++14 -stdlib=libstdc++ -O3 -Wall -Wextra -pedantic-errors 
        -pthread main.cpp && valgrind ./a.out


the following test cases cause errors like this (unless I specify "no errors"):

==5421== Invalid read of size 8
==5421==    at 0x590CBC0: wcscmp (wcscmp.S:208)
==5421==    by 0x4EAC174: std::moneypunct<wchar_t, false>::~moneypunct() (monetary_members.cc:927)
==5421==    by 0x4EAC1D8: std::moneypunct<wchar_t, false>::~moneypunct() (monetary_members.cc:932)
==5421==    by 0x4EA1695: std::locale::_Impl::~_Impl() (locale_classes.h:412)
==5421==    by 0x4EA17D8: std::locale::~locale() (locale_classes.h:521)
==5421==    by 0x400955: main (in /tmp/1412433400.2497/a.out)
==5421==  Address 0x5c2e0b8 is 0 bytes after a block of size 8 alloc'd
==5421==    at 0x4C2AC27: operator new[](unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==5421==    by 0x4EABE61: std::moneypunct<wchar_t, false>::_M_initialize_moneypunct(__locale_struct*, char const*) (monetary_members.cc:847)
==5421==    by 0x4EA3CD7: std::locale::_Impl::_Impl(char const*, unsigned long) (locale_facets_nonio.h:993)
==5421==    by 0x4EA406A: std::locale::locale(char const*) (localename.cc:42)
==5421==    by 0x40094D: main (in /tmp/1412433400.2497/a.out)


cppreference imbue


#include <iostream>
#include <sstream>
#include <locale>

int main()
    std::istringstream iss;

    std::cout << "Current locale: " << iss.getloc().name() << '\n';

    std::cout << "Global locale : " << iss.getloc().name() << '\n';


libstdc++ - errors

libc++ - no errors

The related question in the top given example :

#include <iostream>
#include <locale>

int main (int argc, char **argv) {
    try {
        std::locale * l1 = new std::locale("de_DE.UTF-8");
        delete l1;

        std::locale l2("de_DE.UTF-8");

    } catch(...) {
        return 0;
    return 0;


libstdc++ - errors

libc++ - no errors

The linked bug report in the previous question provided an example :

#include <wchar.h>

void foo(int)

int main()
    wchar_t *a=new wchar_t[2], *b=new wchar_t[2];
    size_t j;


    foo(wcscmp(a, b));
    delete[] a;
    delete[] b;

    return 0;


libstdc++ - no errors

libc++ - no errors

I've added a test case of error reporting for completeness, even if they don't produce errors. Coliru valgrind's version is 3.7.0 and the OP in a related thread mentions upgrading to 3.8.1 and is still accepting errors. I am not on a Linux machine at the moment, so I cannot test it myself. If it matters, here's the glibc output:

GNU C Library (Ubuntu EGLIBC 2.15-0ubuntu10.7) stable release version 2.15, by Roland McGrath et al.
Copyright (C) 2012 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
Compiled by GNU CC version 4.6.3.
Compiled on a Linux 3.2.60 system on 2014-08-28.
Available extensions:
    crypt add-on version 2.1 by Michael Glad and others
    GNU Libidn by Simon Josefsson
    Native POSIX Threads Library by Ulrich Drepper et al
For bug reporting instructions, please see:


Where is the mistake? Examples of cppreference, valgrind or libstdc ++?


source to share

1 answer

This is a false positive in Valgrind recorded here .



All Articles