[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #39 from Jakub Jelinek --- GCC didn't crash with SIGILL. GCC was asked to compile a program with AVX2 instruction set, it has done that. When such a program is run on a hardware that doesn't support some of its instructions, it is termined by the SIGILL signal by the kernel, as hardware raises an exception that there is unknown instruction. What do you expect could GCC done about that?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #38 from John Kanapes --- (In reply to Jakub Jelinek from comment #37) > User error. True. But gcc should complain and handle user errors, not crash with SIGILL:(
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 Jakub Jelinek changed: What|Removed |Added Status|WAITING |RESOLVED Resolution|--- |INVALID --- Comment #37 from Jakub Jelinek --- User error.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #36 from John Kanapes --- That's great news. Thank you so much:) I have to ask: How did you come up with avx? You couldn't even reproduce the problem in your new gccs on newer cpus... I could live with a little better gcc reporting (no SIGILL), but I am very happy with this. Do you need anything more from me?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #35 from John Kanapes --- Changed all my Makefiles to use -mavx acceleration...
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #34 from John Kanapes --- You must be right. I checked in the web and found one more reference that says it has only avx acceleration...
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #33 from Sam James --- As far as I can tell, that CPU might have AVX, but not AVX2.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #32 from John Kanapes --- AMD FX(tm)-8320 Eight-Core Processor
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #31 from Sam James --- What CPU do you have?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #30 from John Kanapes --- I checked without the -mavx2 option, and it worked with -O3 optimization, even with gcc 9.4.0:) It seems that whatever problem is related to that option. Have you tried it with -mavx2 option in 9.5 and 12.1?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #29 from John Kanapes --- Thx for trying it so fast. I assume you have downloaded it, and no longer need the link:) I have no problem with the -mavx2 option. I have gcc 9.4.0, though. Have you tried it with it?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #28 from Jakub Jelinek --- Can't reproduce, neither with gcc 9.5 nor gcc 12.1. You are using -mavx2, are you sure you have AVX2 ISA on the box you're running it?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #27 from John Kanapes --- Hi, I have uploaded my sources to https://www.dropbox.com/s/ao4l5h62h3paujq/test.tgz?dl=0 It is a tar.gzip archive. Expands to a test directory with flat files (10) and 1 Makefile. Main executable is capture. In Ubuntu 20.04 you will also need to install: sudo apt-get install flex sudo apt-get install libuhd3.15 sudo apt-get install libuhd-dev uhd is the ettus driver for their usrp radio. You don't need the radio for the test. Makefile provides 3 targets: (exec), db, clean exec: make without arguments will build capture with -O3 to test bug db: builds capture with gdb flags and without any optimizations clean: cleans all intermediate files and executables Problem reproduction: capture -h Expected response: SIGILL core if built with (exec) Syntax and arguments if built with debug Plz let me know when you have downloaded it, so that I can block the shared link. I can help with all installation and problem reproduction. I will appreciate it, if you can reduce the code before publishing it to a smaller part that can trigger the problem. Gl John
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950
--- Comment #26 from John Kanapes ---
On Tuesday, June 14, 2022 at 06:37:17 PM GMT+3, redi at gcc dot gnu.org
wrote:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950
--- Comment #25 from Jonathan Wakely ---
(In reply to John Kanapes from comment #22)
>> It took you 4 posts to explain me what to do.
>> It took me 4 posts to understand what you were talking about.
>> You should explain better.
>You should read better. Comment 3 is perfectly clear.
>"For UBSan, you can't just compile with -fsanitize=undefined, you need to link
> with that flag as well."
> That
I am sorry, that's not at all clear to me. It tells me that I first need to
compile with fsanitized and then link with it.Since i couldn't even compile
with it, due to the undefined references to ubsan_handles, how could I link?
I tried to link against the -lubsan library, just to get past compilation, and
you told me that this was wrong.Finally I ended up just linking with that flag.
You have to bear in mind, that us programmers do not uselinker flags and do not
know about them:(
How could I explain it bettter?
"fsanitized=undefined is a linker flag. Example: gcc test.o example.o ${LIBS}
fsanitized=undefined -o test"
(In reply to John Kanapes from comment #23)
>> What do you do with the sources after the ticket?
>They will stay attached here. If you don't want them to be public, you need to
>reduce it to something smaller that still shows the bug (which you've said you
>can't) or put them somewhere online and persuade somebody here to download them
>and try to reproduce and reduce it for you.
That is extra work for you. I wasn;t able to do it, and I know the code.
But if you can do smt about it when you find the bug, I would be grateful.I
will upload it to my dropbox account and then send you the link.
TIAJohn
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #25 from Jonathan Wakely --- (In reply to John Kanapes from comment #22) > It took you 4 posts to explain me what to do. > It took me 4 posts to understand what you were talking about. > You should explain better. You should read better. Comment 3 is perfectly clear. "For UBSan, you can't just compile with -fsanitize=undefined, you need to link with that flag as well." (In reply to John Kanapes from comment #23) > What do you do with the sources after the ticket? They will stay attached here. If you don't want them to be public, you need to reduce it to something smaller that still shows the bug (which you've said you can't) or put them somewhere online and persuade somebody here to download them and try to reproduce and reduce it for you.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 Sam James changed: What|Removed |Added CC||sam at gentoo dot org --- Comment #24 from Sam James --- Please be polite on these bugs. There's a lot of documentation online about how to use UBsan. It's not ideal to upload a tarball with all of the bits, but if it's what's needed, then I guess so be it. Some build systems make it easier to enable sanitizers like Meson. GCC's bug tracker isn't for general support on how to use build systems and flags. The bug tracker is public and I don't think one can delete their own attachments. Are you saying that when you use -fsanitize=undefined and run your program, it gets SIGILL'd?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #23 from John Kanapes --- Hi, I have not been able to recreate the issue with simpler programs that use the same resources. I will need to upload my sources. Is it OK to upload a tar.gz archive with a test directory with the sources and a makefile? What do you do with the sources after the ticket? TIA
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #22 from John Kanapes --- OK. Removed -lubsan. Added -fsanitize=undefined to linking Same result as all the other flags. It took you 4 posts to explain me what to do. It took me 4 posts to understand what you were talking about. You should explain better.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #21 from Jonathan Wakely --- What we said is to use -fsanitize=undefined when linking, not add -lubsan manually. I don't know how I could have said that more clearly than comment 6. This is not different to other flags, there are plenty of other flags that are needed both when compiling and linking.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #20 from John Kanapes --- (In reply to Jonathan Wakely from comment #18) > Two of us have already explained that (comment 3 and comment 6, and now > comment 17). I couldn't understand what you were talking about. It is listed with the other -f gcc flags:( To avoid confusion, you could update your in your description that this flag is special and needs to be linked with -lubsan and does that...
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #19 from John Kanapes --- Aaaah. So it's different than the other gcc flags... I just linked libubsan... No compilation errors. At runtime it SIGILLS at the same gdb point as before... Same as the rest of the recommended flags. BTW since -O3 is the highest gcc optimization, gcc could print a warning: Warning -Ox is deprecated. Downgrading to -O3;-) Otherwise in a few years you will find code compiled with -O20 and then it is the sky. It just takes 1 coder to use it in open source, and since gcc seems to take it, all the other coders will copy it:(
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #18 from Jonathan Wakely --- Two of us have already explained that (comment 3 and comment 6, and now comment 17).
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #17 from Jakub Jelinek --- If you mean https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950#c2 , no, you have just posted what is a user error in using the sanitizers and we've told you how to fix that. The -fsanitize=undefined option can't be just added to gcc command line where you compile object files (e.g. if you add it to CFLAGS or CXXFLAGS vars), but also when you link the program (or shared library), so e.g. in LDFLAGS, because when linking it takes care of adding -lubsan to the linker command line.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #16 from John Kanapes --- Good to know (O3). I have posted my -fsanitize=undefined. Doesn't compile with it, but I need help to fix that,because I don't know what it means:( On Tuesday, June 14, 2022 at 02:35:05 PM GMT+3, redi at gcc dot gnu.org wrote: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #15 from Jonathan Wakely --- Just running in GDB doesn't find bugs (and there is no -O6 level, -O3 is the highest). Did you try it with -fsanitize=undefined yet?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #15 from Jonathan Wakely --- Just running in GDB doesn't find bugs (and there is no -O6 level, -O3 is the highest). Did you try it with -fsanitize=undefined yet?
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #14 from John Kanapes --- (In reply to Jakub Jelinek from comment #12) > (In reply to John Kanapes from comment #11) > > (In reply to Richard Biener from comment #9) > > > Note that GCC 9 is no longer supported. Note one common error resulting > > > in > > > SIGILL is when you fall through to an unreachable place which could be > > > padding > > > (like when there's a missing return in a function). > > > > Hmmm. > > gcc 9.40 is the distro gcc for Ubuntu 20.04, which is LTS and still > > supported. > > In this case it is Ubuntu that supports it, so you'd need to ask Ubuntu to > fix it > (if it is a compiler bug of course), because upstream GCC 9.5 was the last > release and there won't be any changes for the GCC 9 series. If it > reproduces with a newer compiler, it can be fixed upstream in the still > supported releases and perhaps Ubuntu could backport it if you ask them to. > > > Does this mean that no action will be taken upon resolving this ticket? > > Depends on if it is reproducible with a supported compiler. That works for me. Both places could use my sources. My work won't be in vain:)
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #13 from John Kanapes --- (In reply to Jakub Jelinek from comment #12) > (In reply to John Kanapes from comment #11) > > (In reply to Richard Biener from comment #9) > > > I am trying to recreate this bug in a smaller, more concise context. > > It is not an obvious bug. This is valid code, and it takes a large chain of > > previous steps to get it wrong at runtime. It used to work with previous > > gccs, but it now seems broken:( > > Claiming it is valid code until it is analyzed is premature. It can very > well be undefined behavior in the code. True. Except that I have already analyzed it with my own tools. That means that the offending code, as reported by gdb, compiles and runs fine with -O6 optimization with a simpler code. I am not claiming anything, just stressing that this is not an obvious issue as reported by gdb, and requires a lot of previous steps to reproduce:(
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #12 from Jakub Jelinek --- (In reply to John Kanapes from comment #11) > (In reply to Richard Biener from comment #9) > > Note that GCC 9 is no longer supported. Note one common error resulting in > > SIGILL is when you fall through to an unreachable place which could be > > padding > > (like when there's a missing return in a function). > > Hmmm. > gcc 9.40 is the distro gcc for Ubuntu 20.04, which is LTS and still > supported. In this case it is Ubuntu that supports it, so you'd need to ask Ubuntu to fix it (if it is a compiler bug of course), because upstream GCC 9.5 was the last release and there won't be any changes for the GCC 9 series. If it reproduces with a newer compiler, it can be fixed upstream in the still supported releases and perhaps Ubuntu could backport it if you ask them to. > Does this mean that no action will be taken upon resolving this ticket? Depends on if it is reproducible with a supported compiler. > I am trying to recreate this bug in a smaller, more concise context. > It is not an obvious bug. This is valid code, and it takes a large chain of > previous steps to get it wrong at runtime. It used to work with previous > gccs, but it now seems broken:( Claiming it is valid code until it is analyzed is premature. It can very well be undefined behavior in the code.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #11 from John Kanapes --- (In reply to Richard Biener from comment #9) > Note that GCC 9 is no longer supported. Note one common error resulting in > SIGILL is when you fall through to an unreachable place which could be > padding > (like when there's a missing return in a function). Hmmm. gcc 9.40 is the distro gcc for Ubuntu 20.04, which is LTS and still supported. Does this mean that no action will be taken upon resolving this ticket? I am trying to recreate this bug in a smaller, more concise context. It is not an obvious bug. This is valid code, and it takes a large chain of previous steps to get it wrong at runtime. It used to work with previous gccs, but it now seems broken:( It will remain broken in future releases unless we stop it here:( I hope you reconsider:) If that was a problem of a missing return in a function, it would have to be an internal function. The spot it happens is in main initialization, before it had a chance to call any of my functions.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #10 from Jonathan Wakely --- (In reply to John Kanapes from comment #8) > I hope, I have a couple of days before closing this ticket:) Yes, we usually let a bug sit in WAITING status for a couple of months before closing it, so you have plenty of time.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #9 from Richard Biener --- Note that GCC 9 is no longer supported. Note one common error resulting in SIGILL is when you fall through to an unreachable place which could be padding (like when there's a missing return in a function).
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #8 from John Kanapes --- True. I was confused that sources were needed only by the GNAT subsystem. I am working to recreate the issue in a smaller, more portable, easier to understand code. I hope, I have a couple of days before closing this ticket:)
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #7 from Jonathan Wakely --- (In reply to John Kanapes from comment #2) > The missing info, gcc -v -save-temps is provided as an attachment. But we're still missing the code that triggers the bug. A bug report that just says something goes wrong will be closed. We need the code to figure out what goes wrong and fix it.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #6 from Jonathan Wakely --- Line numbers in the source code aren't relevant here, you need to add the -fsanitize=undefined flag to your link command to solve those undefined references.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #5 from John Kanapes --- Thank you for taking the time to look at it, and responding so fast:)
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #4 from John Kanapes --- I don't know UBSan. What's more these are not user-friendly, compiler errors. It reminds me of assemblers:( I need readable errors with line numbers, otherwise I don't know what to change:(
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #3 from Jakub Jelinek --- For UBSan, you can't just compile with -fsanitize=undefined, you need to link with that flag as well.
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 --- Comment #2 from John Kanapes --- Hi, The missing info, gcc -v -save-temps is provided as an attachment. Of the flags, Wextra, -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations did nothing. -fsanitize=undefined creates the following output for main: usr/bin/ld: capture.o: in function `main.cold': capture.c:(.text.unlikely+0x112): undefined reference to `__ubsan_handle_load_invalid_value' /usr/bin/ld: capture.c:(.text.unlikely+0x13a): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x16b): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x19c): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x1cd): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x1f6): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.o:capture.c:(.text.unlikely+0x21f): more undefined references to `__ubsan_handle_nonnull_arg' follow /usr/bin/ld: capture.o: in function `main.cold': capture.c:(.text.unlikely+0x35e): undefined reference to `__ubsan_handle_load_invalid_value' /usr/bin/ld: capture.c:(.text.unlikely+0x381): undefined reference to `__ubsan_handle_load_invalid_value' /usr/bin/ld: capture.c:(.text.unlikely+0x3a1): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x3c1): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x3e1): undefined reference to `__ubsan_handle_nonnull_arg' /usr/bin/ld: capture.c:(.text.unlikely+0x409): undefined reference to `__ubsan_handle_load_invalid_value' /usr/bin/ld: capture.c:(.text.unlikely+0x42a): undefined reference to `__ubsan_handle_load_invalid_value' /usr/bin/ld: capture.o: in function `main': capture.c:(.text.startup+0xa2d): undefined reference to `__ubsan_handle_pointer_overflow' /usr/bin/ld: capture.c:(.text.startup+0x1042): undefined reference to `__ubsan_handle_sub_overflow' /usr/bin/ld: capture.c:(.text.startup+0x1053): undefined reference to `__ubsan_handle_out_of_bounds' /usr/bin/ld: capture.c:(.text.startup+0x1067): undefined reference to `__ubsan_handle_pointer_overflow' /usr/bin/ld: capture.c:(.text.startup+0x107e): undefined reference to `__ubsan_handle_pointer_overflow' /usr/bin/ld: capture.c:(.text.startup+0x1092): undefined reference to `__ubsan_handle_type_mismatch_v1' collect2: error: ld returned 1 exit status
[Bug c/105950] > O2 optimization causes runtime (SIGILL) during main initialization
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105950 Jonathan Wakely changed: What|Removed |Added Status|UNCONFIRMED |WAITING Ever confirmed|0 |1 Last reconfirmed||2022-06-13 --- Comment #1 from Jonathan Wakely --- Please provide the missing info requested by https://gcc.gnu.org/bugs and also try using -fsanitize=undefined and the other flags suggested there.
