GCC compiles and links a program with a function that should return a value, yet doesn't. This violates the definition of a value-returning function. See pp. 148 in "The C++ Programming Language: 3rd ed.". Example program: ====================START OF PROGRAM==================== /** ** \author Robert Miesen ** \date 09/04/2007 -- Time-stamp: \<09/04/2007\> ** \version 1.0 ** \file main.cpp ** \brief Contains code to demonstrate a bug in GCC: that it doesn't flag cases where a function that should return a value doesn't. ** ** \remarks Input: ** - N/A. ** \remarks Output: ** - TBD. ** \remarks Exit Codes: ** - 0: Normal Execution **/ #include <iostream> // // Function Prototypes: // bool Func1(int param1); int main( int argc, char *argv[] ) { std::cout << "The value of 5*5 is: " << Func1(5) << "\n"; return 0; } bool Func1(int param1) { int var1 = param1*param1; // Hay, I didn't specify a return value...this shouldn't compile (but it does!) } ====================END OF PROGRAM==================== And wait, it gets worse! Just compile this sucker with -O2 optimizations and you get RANDOM RETURN VALUES from the call of Func1! System information: gcc: Using built-in specs. Target: i686-pc-linux-gnu Configured with: /var/tmp/portage/sys-devel/gcc-4.2.0/work/gcc-4.2.0/configure --prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.2.0 --includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.2.0/include --datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.2.0 --mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.2.0/man --infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.2.0/info --with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.2.0/include/g++-v4 --host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec --enable-nls --without-included-gettext --with-system-zlib --disable-checking --disable-werror --enable-secureplt --disable-libunwind-exceptions --disable-multilib --enable-libmudflap --disable-libssp --disable-libgcj --with-arch=i686 --enable-languages=c,c++,fortran --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu Thread model: posix gcc version 4.2.0 (Gentoo 4.2.0 p1.4)
it's a feature, not a bug and of course you'll get random return values ... you'll get whatever happens to be in the %eax if you want a different answer, open a bug at http://gcc.gnu.org/
