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Conditional jump or move depends on uninitialised value(s) for std::wistringstream

Tags:

c++

valgrind

wchar-t

I have stolen the following code snippet from cppreference.com and adopted it for usage of wchar_t:

#include <string>
#include <iostream>
#include <sstream>

template <typename T>
struct test_seq {};

template <>
struct test_seq<char> {
    std::string operator()() {
        return "1\n2\n3\n4\n5\n6\n7\n";
    }
};

template <>
struct test_seq<wchar_t> {
    std::wstring operator()() {
        return L"1\n2\n3\n4\n5\n6\n7\n";
    }
};

int main(int, char **) {
    using char_t = wchar_t;

    std::basic_istringstream<char_t> input;

    test_seq<char_t> seq;
    input.str(seq());

    int sum = 0;
    for (std::basic_string<char_t> token; std::getline(input, token);) {
        sum += std::stoi(token);
    }
    std::cout << "The sum is: " << sum << "\n";

    return 0;
}

It comes as no surprise, that changing char_t to char does not affect the value of sum and the program exits successfully.

Anyhow, analyzing both versions with valgrind via valgrind --leak-check=full --leak-resolution=med --track-origins=yes ... causes a huge error log for the wchar_t case, whereas everything is fine for char. Valgrind's error log reads:

==1== Memcheck, a memory error detector
==1== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==1== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==1== Command: ./a.out
==1== Parent PID: 0
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x55715C7: __wmemchr_avx2 (memchr-avx2.S:250)
==1==    by 0x4EE8B54: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x4EE8B80: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x4F7AD08: std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_M_append(wchar_t const*, unsigned long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x4EE8B93: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x4F7AD0D: std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_M_append(wchar_t const*, unsigned long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x4EE8B93: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x4F7AD17: std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_M_append(wchar_t const*, unsigned long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x4EE8B93: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Use of uninitialised value of size 8
==1==    at 0x4F7AD25: std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_M_append(wchar_t const*, unsigned long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x4EE8B93: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x4EE8BA7: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)

[...]

==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x55713EE: __wmemchr_avx2 (memchr-avx2.S:58)
==1==    by 0x4EE8B54: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Use of uninitialised value of size 8
==1==    at 0x5571437: __wmemchr_avx2 (memchr-avx2.S:92)
==1==    by 0x4EE8B54: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x5571443: __wmemchr_avx2 (memchr-avx2.S:97)
==1==    by 0x4EE8B54: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x557144C: __wmemchr_avx2 (memchr-avx2.S:102)
==1==    by 0x4EE8B54: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Use of uninitialised value of size 8
==1==    at 0x4F7AD70: std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_M_append(wchar_t const*, unsigned long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x4EE8B93: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== Conditional jump or move depends on uninitialised value(s)
==1==    at 0x4F572EA: std::__cxx11::basic_stringbuf<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::underflow() (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x4EE8D69: std::basic_istream<wchar_t, std::char_traits<wchar_t> >& std::getline<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >(std::basic_istream<wchar_t, std::char_traits<wchar_t> >&, std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >&, wchar_t) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
==1==    by 0x109128: main (test.cxx:31)
==1== 
==1== 
==1== HEAP SUMMARY:
==1==     in use at exit: 0 bytes in 0 blocks
==1==   total heap usage: 4 allocs, 4 frees, 76,920 bytes allocated
==1== 
==1== All heap blocks were freed -- no leaks are possible
==1== 
==1== For counts of detected and suppressed errors, rerun with: -v
==1== ERROR SUMMARY: 48 errors from 20 contexts (suppressed: 0 from 0)

What is going on? Do I misuse std::istringstream and / or std::getline?

like image 258
avitase Avatar asked Aug 16 '18 17:08

avitase

People also ask

What is conditional jump or move depends on Uninitialised value S?

Conditional jump or move depends on uninitialized value(s)This error is caused if you forget to initialize variables before using or accessing them. You can usually re-run valgrind with the flag --track-origins=yes to see where the uninitialized value came from.

How do you fix conditional jumps?

The conditional jump or move depends on uninitialised value(s) error can be fixed by initializing the word inside the NULL function. This is a common problem web developers face where this jump is going to affect the rest of the document and render it incorrectly.

1 Answers

This is probably already resolved Valgrind bug https://bugs.kde.org/show_bug.cgi?id=388862.

Try to build Valgrind from current sources http://valgrind.org/downloads/repository.html and see if the bug still persists.

like image 95
ks1322 Avatar answered Sep 21 '22 14:09

ks1322
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