[Bug libstdc++/113159] More robust std::sort for silly comparator functions

[jengelh at inai dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113159

--- Comment #18 from Jan Engelhardt <jengelh at inai dot de> ---
_GLIBCXX_DEBUG sounds good. Though, it can only be switched per TU so one would
have to get even more creative to do something like

void f(std::vector<int> &a, std::vector<int> &b)
{
    // "I know I got this"
    std::sort(a.begin(), a.end(), [](int a, int b) { return a < b; });

    // Trust no one
    auto uc = reinterpret_cast<bool (*)(int,int)>(dlsym(nullptr,
"user_compare"));
#define _GLIBCXX_DEBUG
    std::sort(b.begin(), b.end(), uc);
#undef _GLIBCXX_DEBUG
}