Segmentaton fault in testing length of std::wstring

Question

I just don't get it. I have a function to read stemmed strings from a List, check each string if it contains a punctuation marker to and build phrases in a loop of the single word images. When I check the string building/containing the phrase with s.length() > 0 in the if-statement I get a seg fault. Here is the function:

std::wstring
Phrase::userFriendlyTerms() {
    std::wstring s = L"";

    List<Object> *terms = getTerms();

    Iterator<Object> *i = terms->iterator();
    for (; i->hasNext();) {
        StemmedTerm *t = (StemmedTerm *) i->next();
        std::wstring image = t->getTerm();

        // --- gdb shows me a seg. fault with s.length()
        if (s.length() > 0 &&
            !((image.compare(L",") == 0) || (image.compare(L"?" == 0))
                || (image.compare(L"!") == 0)
                || (image.compare(L";") == 0))) {
            s.append(L" ");
        }
        s.append(image);
    }   
    delete i;

    return s;
}

Exact error message is:

Program received signal SIGSEGV, Segmentation fault.
__wcslen (s=0x0) at wcslen.c:30
30  wcslen.c: No such file or directory.
    in wcslen.c
(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) n
Program not restarted.
(gdb) backtrace
#0  __wcslen (s=0x0) at wcslen.c:30
#1  0x00007ffff7b89e56 in std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::compare(wchar_t const*) const () from /usr/lib/libstdc++.so.6
#2  0x00000000004833ed in Phrase::userFriendlyTerms (this=0x1425ac0) at algorithm/Phrase.cpp:56

Maybe I am blind or missing something ...

Thanks for your help!

Answer 1

this here looks suspicious

(image.compare(L"?" == 0)

are you sure you didn't mean

(image.compare(L"?") == 0)