Bug#196908: g++-3.3: inconsistent behaviour of -Wall

[giuseppe bonacci <g.bonacci@libero.it>]

Package: g++-3.3
Version: 1:3.3-3
Severity: normal
Tags: security

I don't know whether g++-3.3 or libstdc++5-3.3-dev is responsible. 
Anyway, here it is:

$ cat a.cc
#include <iostream>
#include <vector>
template <class T> static inline T f(T x) {
        T y;
        return y;
}
int main() {
    std::vector<int> a;
    a.push_back(12);
    std::cout << *f(a.begin()) << '\n';
}

$ cat b.cc
#include <iostream>
#include <vector>
template <class T> static inline T f(T x) {
        T y;
        return y;
}
int main() {
    int b[] = { 34 };
    std::cout << *f(b) << '\n';
}

Now compare the output from g++ on the above files:

$ g++ -O -W -Wall -ansi -pedantic a.cc
$ g++ -O -W -Wall -ansi -pedantic b.cc
b.cc: In function `int main()':
b.cc:7: warning: `int*y' might be used uninitialized in this function

That is, the same template function f issues a (correct) warning
when instantiated for T = int *, but not when instantiated for T =
std::vector<int>::iterator

This behaviour might cause dereferencing invalid iterators
-- uninitialized or initialized by constructor to some default value --
going unnoticed, and eventually raise security issues in setuid executables.

g.b.

-- System Information:
Debian Release: testing/unstable
Architecture: i386
Kernel: Linux bonacci 2.4.20-3-686 #1 Sun May 18 20:26:19 EST 2003 i686
Locale: LANG=C, LC_CTYPE=C

Versions of packages g++-3.3 depends on:
ii  gcc-3.3                       1:3.3-3    The GNU C compiler
ii  gcc-3.3-base                  1:3.3-3    The GNU Compiler Collection (base 
ii  libc6                         2.3.1-16   GNU C Library: Shared libraries an
ii  libstdc++5-3.3-dev            1:3.3-3    The GNU Standard C++ Library v3 (d

-- no debconf information