FS#1464 - Perl built with gcc > v5 segfaults on apm821xx #6704
Comments
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chunkeey: [[https://github.com/arsv/perl-cross/issues/60|perl-cross issue #60]] suggests that the gcc version detection code broke. arsv mentioned a fix and it seems that manually forcing "-fwrapv -fno-strict-aliasing" did the trick here. (See attached patch.) I had to completely purge the old perl installation too. the --force-reinstall did not on local packages. |
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russell: That fixes it for me. |
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diizzyy: Still an issue, perhaps ping Philip on Github (where this should have been reported on in the first place as it's in the package repo)? |
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russell: diizzyy, it was reported here intentionally, because it was/is not clear if this is a general build system problem for apm821xx, or a problem that is specific to the perl package. |
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pprindeville: Russell, if other things required this flag they'd be failing too. Seems to be pretty specific to Perl5. |
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pprindeville: Spoke to Tony Cook and it seems that much of Perl was written relying on the undefined behavior of signed overflow wrapping around (i.e. exactly what -fwrapv controls). Ideally someone would scrub this out of Perl, but until then, the workaround is to build with this flag. Fixed with PR #6623. |
russell:
I have seen this on recent builds for Meraki MR24 (apm821xx)
Currently at commit db893ec.
Noticed recently since the update to gcc version 7 as default (at commit 61eee1a).
Using GCC_USE_VERSION_5=y builds a perl that doesn't segfault. GCC_USE_VERSION_6=y also segfaults. Perl installed is 5.26.1-3
Start perl, type "use strict;" followed by a carriage return. BOOM
root@hostname:/# perl
use strict;
Attempt to free unreferenced scalar: SV[65050.255294] perl[16847]: unhandled signal 11 at 529303c4 nip b7a193b4 lr b7a19380 code 1
0x10493190 at /usr/lib/perl5/5.26/strict.pm line 38.
Segmentation fault
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