Lauri Kasanen schrieb:
On Sun, Mar 30, 2014, at 15:05, Ralf Friedl wrote:I'm seeing busybox dc acting funny when compiled with some versions of gcc. This is on busybox git. The x86 binary busybox_unstripped and config are attached.gcc 4.2.2 - ok gcc 4.7.2: nc 10 1 add p 2.738e+93 So either bb is hitting a compiler bug, or undefined behavior somewhere with new gcc's more aggressive optimizations.I have 4.7.2 on x86 and I get 11 as output. You could add debug output to push and pop to see what happens.I think it's related to http://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html which hit the radeon driver as well http://lists.freedesktop.org/archives/dri-devel/2013-August/044122.html but changing the stack[1] to stack[0], stack[], or even stack[10] did not fix the issue.
If the change didn't fix it, then maybe it's not related to that.
What's even worse is that adding any output to push(), even a puts("hi")
that does not print the argument or any of the stack vars, fixes it. So
something magic is going on inside the GCC optimization, I'm afraid this
is above my pay grade.
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