Thread: In GDB no segmentation fault but while running segmentation fault

when you access txtF[pos] you never check that pos is not out-of-bounds

also you should not use magic numbers 97 and 122

It's crashing because you don't check for non-alphabetic characters in the loop that counts the frequencies. Something like this will fix it:

Code:

        for(int i = 0; i < cipherText.size(); ++i) {
            char c = tolower(cipherText[i]);
            if (c < 'a' || c > 'z')
                continue;
            ++cipherF[c - 'a'].frequency;
        }

Without that check, the exclamation point at the end of "dummy!" will cause the incrementation of cipherF[-64]. This apparently overwrites something critical and the program crashes when main returns.

When the program runs under gdb, it has a somewhat different layout and the crash doesn't happen.