Edit report at https://bugs.php.net/bug.php?id=79356&edit=1
ID: 79356
Updated by: dmi...@php.net
Reported by: vibhutisawant18 at gmail dot com
Summary: FFI:structure/union alignment
[ext/ffi/tests/022.phpt] failure
Status: Assigned
Type: Bug
Package: Testing related
Operating System: Ubuntu 16.04
PHP Version: master-Git-2020-03-09 (Git)
Assigned To: dmitry
Block user comment: N
Private report: N
New Comment:
@nikic: I don't know, but in case GCC supports this, I would prefer to support
this as well.
The proposed fix https://github.com/php/php-src/pull/5256
Previous Comments:
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[2020-03-11 09:11:56] ni...@php.net
@dmitry: Do you know of some particular case where this is being used?
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[2020-03-11 09:07:00] dmi...@php.net
I'm not sure, if we should remove support for __attribute__((aligned)) without
specified alignment completely. Probably, we should export
__BIGGEST_ALIGNMENT__ constant and may be add a warning about dependency.
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[2020-03-09 10:24:04] ni...@php.net
@dmitry: I would suggest that we remove support for __attribute__((aligned))
without specified alignment, because it is not interoperable. If PHP was
combined with a different target architecture than the library we're linking
against, the alignment will be incorrect. We should force an explicit
specification of the alignment instead. What do you think?
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[2020-03-09 10:21:18] ni...@php.net
Okay, I see now. __attribute__((aligned)) is the same as
__attribute__((__BIGGEST_ALIGNMENT__)). I happened to use an -march=sandybridge
build, where __BIGGEST_ALIGNMENT__ is 32.
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[2020-03-09 10:09:21] ni...@php.net
Something odd is going on here. The test passes for me on 7.4, but fails on
master. Adding a bit more debug output I get:
FAIL: sizeof(struct {char a; uint32_t b __attribute__((aligned));})
Expected: 32
Actual: 64
FAIL: alignof(struct {char a; uint32_t b __attribute__((aligned));})
Expected: 16
Actual: 32
So I'm seeing a higher size/alignment for some reason.
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