andrew wiggin <end3er@xxxxxxxxx> writes: > I have recently met a segfault in a program I had to port from x86 to > ARMv7. After some investigation I managed to narrow it down to a few > C++ lines which when compiled with -O > 0 will always produce an > incorrect assembly on ARM. > > I am using GCC 4.2.1 for ARM. > > The register R1 holding the pointer to the construction vtable for the > Parent-in-Child is actually pointing to the wrong Parent-in-Child > vtable: > Let's assume we have a virtual base class A, two derived class B and C > virtually inheriting from A and a final class D derived from B and C. > When instantiating D, the CTOR for B is called with R1 pointing to the > construction vtable for C-in-D instead of the one for B-in-D, which > thus make the program crash since it tries to access an uninitialized > element of the vtable for C when trying to access elements in B. (I > hope it is clear enough). Your C++ code looks OK to me. I guess the first thing I would recommend is trying a newer version of gcc to see if the bug has been fixed. > It seems to be related to bug: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41354 however the > -fno-tree-sink doesn't resolve the issue, so I am assuming that it is > not a duplicate. I would guess that it is the same underlying problem, though: a problem with alias analysis leading to invalid stack slot sharing. That bug should be fixed in gcc 4.5. Ian
