Segfault when building with gcc 7 #60
Comments
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Note that switching back to gcc 6 for miniperl itself fixes it |
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Can you post xconfig.sh and maybe also config.log from this build somewhere? No segfaults for me on x86_64 host with gcc 7.2.1, and valgrind reports nothing. |
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Sure, here's a build log, xconfig.sh, and config.log https://gist.github.com/shlevy/ade184d2b0f2ff59f17e55e74e97ccfb. It's extra verbose to show all the extra flags we pass to our compiler. This is for |
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Ok I think I got it. GCC 4.9 and above needs -fwrapv to build perl. The fix wasn't applied properly to gcc-7.x, and perl-cross failed to detect gcc version in your hardened setup anyway. This only matters for -O2 and above, in particular -Os builds work just fine. If possible, please try this branch: https://github.com/arsv/perl-cross/tree/nix The underlying issue: https://rt.perl.org/Public/Bug/Display.html?id=121505 |
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Great, that worked! Do we need that patch for non-cross-compiled perl? NixOS/nixpkgs@b45fb43 |
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Probably not. Unless you use perl-cross for native builds, which doesn't seem to be the case. Mainline Configure from perl-5.24 should be able to handle gcc-7, no changes are needed there. If unsure, check config.sh for -fwrapv in ccflags. |
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I'm still seeing this with perl 5.24.1 cross compiled with perl-cross 1.9 via a gentoo ebuild. Are there any other possible fixes for this? "-fwrapv" is in my cflags. |
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Same exact segfault? Can you post xconfig.sh and config.log somewhere? There's also -fno-strict-aliasing, but if -fwrapv is there the other one should be as well. Check also for -O3 or any standalone -f-something, especially if the target is unusual. Maybe try building it with -O0 or -Os. |
In developer containers or SDK, there has been a bug in cross-compiled
perl that it crashes with segmentation fault. It has two different
reasons:
The first issue is that perl depends on perl-cross 1.1.4, which has a
bug with gcc 7.x or newer, so that the necessary CFLAGS `-fwrapv` was
not appended. This issue was fixed in perl-cross 1.1.9 or newer. So we
just need to upgrade perl-cross to 1.2.2, the newest release.
```
CROSS_VER=1.2.2
```
The other issue is that the CFLAGS `-O2` was given when building
cross-compiled perl. We should replace the optimization flag with `-O0`,
when it's built by the cross compiler. Without that, the segfault will
not be fixed at all.
```
if tc-is-cross-compiler; then
replace-flags -O? -O0
fi
```
How to test inside the Flatcar SDK environment:
```
LD_PRELOAD=/build/amd64-usr/usr/lib/libperl.so.5.24.1 /build/amd64-usr/usr/bin/perl -V
```
See also coreos/bugs#2369
coreos/bugs#2545
arsv/perl-cross#60
In developer containers or SDK, there has been a bug in cross-compiled
perl that it crashes with segmentation fault. It has two different
reasons:
The first issue is that perl depends on perl-cross 1.1.4, which has a
bug with gcc 7.x or newer, so that the necessary CFLAGS `-fwrapv` was
not appended. This issue was fixed in perl-cross 1.1.9 or newer. So we
just need to upgrade perl-cross to 1.2.2, the newest release.
```
CROSS_VER=1.2.2
```
The other issue is that the CFLAGS `-O2` was given when building
cross-compiled perl. We should replace the optimization flag with `-O0`,
when it's built by the cross compiler. Without that, the segfault will
not be fixed at all.
```
if tc-is-cross-compiler; then
replace-flags -O? -O0
fi
```
How to test inside the Flatcar SDK environment:
```
LD_PRELOAD=/build/amd64-usr/usr/lib/libperl.so.5.24.1 /build/amd64-usr/usr/bin/perl -V
```
See also coreos/bugs#2369
coreos/bugs#2545
arsv/perl-cross#60
There has been a bug that cross-compiled perl crashes with segmentation fault. It has two different reasons: first, perl-cross didn't append CFLAGS `-fwrapv` in case of gcc 7.x or newer, and the other is that the CFLAGS still contained `-O2`. The first issue was recently fixed by setting `CROSS_VER` to `1.2.2`. On the other hand, the second issue is not fixed yet, so perl still segfaults in case of a cross-compiled version. So let's fix it by replacing `-O?` with `-O2`. For example, how to test inside a cross-compilation SDK environment: ``` LD_PRELOAD=/build/amd64-usr/usr/lib/libperl.so.5.24.1 /build/amd64-usr/usr/bin/perl -V ``` See also coreos/bugs#2369 coreos/bugs#2545 arsv/perl-cross#60 Signed-off-by: Dongsu Park <[email protected]>
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I had this problem back in February. I think I stumbled across this report, worked around it, then forgot about it until just now when I ran into it again. I can confirm that I usually use |
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Current defaults are |
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Oh hai @chewi, fancy seeing you here. Just reporting that under cross compile, the built perl still segfaults this way w/ perl 5.30.3 w/ cross 1.3.4 & GCC 10. This caused a significant amount of "fun" for building a scratch VM for m68k as it means autoconf and friends like to fail :) Fortunately, with enough brute force, natively building perl under emulation was achievable, and didn't suffer this problem. |
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For issues like this, it would be really nice to have config.sh from the failing cross build, and also the one from a successful build if available. It's very difficult to tell what's going on otherwise. Given the rest of this issue, the first thing I would be looking for is which compiler flags were actually used for either build. |
We recently switched nixpkgs to gcc 7, and now our perl cross-builds fail with:
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