On x86_64 (but not on i686) the following legal code sends gcc 3.2.3, 3.3.4 and current 3.3-branch CVS into an infinite loop.
///////////////////////////////////////// struct Base1 { }; struct Base2 { }; struct Base3 { }; struct Derived : Base1, Base2, Base3 { }; void foo(Derived); int main() { foo(Derived()); } ////////////////////////////////////////// The problem appears to be in classify_argument in gcc/config/i386.c: in both the RECORD_TYPE and UNION_TYPE branches, the same loop variable (i) is used in two nested loops. I'm not sure I fully understand this code, but it seems unlikely that this is the intention. I'm also not sure if it's possible for this to result in other failure modes besides the infinite loop, although it certainly seems possible. Using two distinct loop variables appears to fix the problem -- a patch will follow after I've done testsuite runs on current CVS. (Looking at the source, the above problem appears to still be present on the 3.4 branch and CVS HEAD, although I've not tested there yet.) -- Summary: Infinite loop when passing object with 3+ base classes by value Product: gcc Version: 3.3.4 Status: UNCONFIRMED Severity: normal Priority: P2 Component: target AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: zak at transversal dot com CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: x86_64-pc-linux-gnu GCC host triplet: x86_64-pc-linux-gnu GCC target triplet: x86_64-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18300