"go version" on powerpc-linux-gnu works with the 5.1 release candidate, but crashes with the 5.1.0 release, and the current branch. reverting the changes made in PR65787 fixes the issue. Seen on Ubuntu 15.04 and 15.10 systems, however I can't reproduce this in Debian unstable. Same binutils version, Debian has glibc-2.19, Ubuntu glibc-2.21. It looks like I can't reproduce this with a GCC trunk build on either platform. So I'm a bit lost ... $ go version fatal error: unexpected signal during runtime execution [signal 0xb code=0x1 addr=0x3] goroutine 16 [running]: runtime_dopanic ../../../src/libgo/runtime/panic.c:131 runtime_throw ../../../src/libgo/runtime/panic.c:193 sig_panic_leadin ../../../src/libgo/runtime/go-signal.c:247 sig_panic_info_handler ../../../src/libgo/runtime/go-signal.c:281 :0 __go_go ../../../src/libgo/runtime/proc.c:2328 runtime_main ../../../src/libgo/runtime/proc.c:598 goroutine 0 [idle]: panic during panic goroutine 0 [idle]: runtime_dopanic ../../../src/libgo/runtime/panic.c:131 runtime_startpanic ../../../src/libgo/runtime/panic.c:100 runtime_throw ../../../src/libgo/runtime/panic.c:191 runtime_gogo ../../../src/libgo/runtime/proc.c:251 runtime_tracebackothers ../../../src/libgo/runtime/proc.c:767 runtime_dopanic ../../../src/libgo/runtime/panic.c:139 runtime_throw ../../../src/libgo/runtime/panic.c:193 sig_panic_leadin ../../../src/libgo/runtime/go-signal.c:247 sig_panic_info_handler ../../../src/libgo/runtime/go-signal.c:281 :0 __go_go ../../../src/libgo/runtime/proc.c:2328 runtime_main ../../../src/libgo/runtime/proc.c:598
correction: reverting the changes from PR65787 only helps for the 5.1.0 release, not the gcc-5-branch.
maybe the changes from PR65787 are unrelated. Building a compiler which has -fstack-protector strong enabled by default. The crash goes away when I add -fno-stack-protector to AM_CFLAGS in libgo. So it should be reproducible by adding -fstack-protector strong to AM_CFLAGS in libgo. Don't know why this shows up only now, and on powerpc-linux-gnu only.
Let's get the obvious set up questions out of the way first... If you are building on Ubuntu, I assume you must be trying to build powerpc64le-linux-gnu, and not powerpc-linux-gnu. Is your LD_LIBRARY_PATH being set to the correct path for the libgo that corresponds to the go and gccgo you are using? That is, you aren't using libgo from a gcc trunk build but go and gccgo from a gcc5 build?
No, this is specifically about powerpc-linux-gnu. powerpc64le works fine. As for the library path questions, this first came up in runtime bug reports, and has been confirmed by many on clean chroots, so no, there aren't random libraries kicking around from other builds. doko's stack-protector discovery makes perfect sense as to why this works fine on Debian but not Ubuntu, as that's really the only difference between our two toolchains. Now, the question is *why*, and why only on ppc32? (Or maybe only on big-endian PPC, neither of us has tested a powerpc64-linux-gnu build yet).
building trunk libgo with -fstack-protector-strong yields: $ go version fatal error: unexpected signal during runtime execution [signal 0xb code=0x1 addr=0x3] goroutine 16 [running]: :0 :0 :0 :0 [...] building libgo and libbacktrace with -fstack-protector-strong yields: fatal error: unexpected signal during runtime execution [signal 0xb code=0x1 addr=0x3] goroutine 16 [running]: runtime_dopanic ../../../src/libgo/runtime/panic.c:131 runtime_throw ../../../src/libgo/runtime/panic.c:193 sig_panic_leadin ../../../src/libgo/runtime/go-signal.c:247 sig_panic_info_handler ../../../src/libgo/runtime/go-signal.c:281 :0 __go_go ../../../src/libgo/runtime/proc.c:2328 runtime_main ../../../src/libgo/runtime/proc.c:598 goroutine 0 [idle]: panic during panic goroutine 0 [idle]: runtime_dopanic ../../../src/libgo/runtime/panic.c:131 runtime_startpanic ../../../src/libgo/runtime/panic.c:100 runtime_throw ../../../src/libgo/runtime/panic.c:191 runtime_gogo ../../../src/libgo/runtime/proc.c:251 runtime_tracebackothers ../../../src/libgo/runtime/proc.c:767 runtime_dopanic ../../../src/libgo/runtime/panic.c:139 runtime_throw ../../../src/libgo/runtime/panic.c:193 sig_panic_leadin ../../../src/libgo/runtime/go-signal.c:247 sig_panic_info_handler ../../../src/libgo/runtime/go-signal.c:281 :0 __go_go ../../../src/libgo/runtime/proc.c:2328 runtime_main ../../../src/libgo/runtime/proc.c:598
I think you've said the problem only occurs when using -fstack-protector-strong and when building with glibc-2.21. Have you tried using gdb to see where the segv actually occurs? >gdb go ..... >run version (Once it hits the segv) >x/20ni $pc-24 >bt The panic stacktrace is showing a line in proc.c:2328 which is making a call to __builtin_return_address according to my source. Does that match your source? If that is the case then I have a feeling this isn't go specific, but a problem with calling __builtin_return_address on ppc32 when using -fstack-protector-strong and possibly glibc-2.21 has some affect.
FYI, PR65787 only changes behavior for powerpc64le, so it's odd that you would see any differences with or without those changes. The two patched routines are never called for big endian.
GCC 5.2 is being released, adjusting target milestone to 5.3.
I'm not having any luck reproducing this. I built a 32-bit PPC GNU/Linux (on the GCC compile farm, which is a PPC64 machine, using glibc 2.18). I deleted the libgo files and rebuilt them with -fstack-protector-strong. I built a new go tool. It seems to work fine. Let's try this: if you can still recreate this problem, send me the crashing binary. Maybe I can see something there.
GCC 5.3 is being released, adjusting target milestone.
GCC 5.4 is being released, adjusting target milestone.