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List:       php-qa
Subject:    Bug #79356 [Opn]: FFI:structure/union alignment [ext/ffi/tests/022.phpt] failure
From:       nikic () php ! net
Date:       2020-03-09 10:24:04
Message-ID: E1jBFZs-00052c-E6 () bugs ! php ! net
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Edit report at https://bugs.php.net/bug.php?id=79356&edit=1

 ID:                 79356
 Updated by:         nikic@php.net
 Reported by:        vibhutisawant18 at gmail dot com
 Summary:            FFI:structure/union alignment
                     [ext/ffi/tests/022.phpt] failure
 Status:             Open
 Type:               Bug
 Package:            Testing related
 Operating System:   Ubuntu 16.04
 PHP Version:        master-Git-2020-03-09 (Git)
-Assigned To:        
+Assigned To:        dmitry
 Block user comment: N
 Private report:     N

 New Comment:

@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?


Previous Comments:
------------------------------------------------------------------------
[2020-03-09 10:21:18] nikic@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.

------------------------------------------------------------------------
[2020-03-09 10:09:21] nikic@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.

------------------------------------------------------------------------
[2020-03-09 09:50:26] vibhutisawant18 at gmail dot com

ext/ffi/tests/022.phpt passed on x86-64.PFB the test log.

root@a11efdc33877:~/php/php-src# sapi/cli/php -f "ext/ffi/tests/022.phpt"
--TEST--
FFI 022: structure/union alignment
--SKIPIF--
--INI--
ffi.enable=1
--FILE--
ok
--EXPECT--
ok
root@a11efdc33877:~/php/php-src# arch
x86_64
root@a11efdc33877:~/php/php-src#

------------------------------------------------------------------------
[2020-03-09 08:17:12] nikic@php.net

This test also fails for me on a x86-64, so not big endian specific.

------------------------------------------------------------------------
[2020-03-09 05:53:16] vibhutisawant18 at gmail dot com

The following patch has been added/updated:

Patch Name: FFI_structure_union_alignment_s390x
Revision:   1583733196
URL:        https://bugs.php.net/patch-display.php?bug=79356&patch=FFI_structure_union_alignment_s390x&revision=1583733196


------------------------------------------------------------------------


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the rest of the comments, please view the bug report online at

    https://bugs.php.net/bug.php?id=79356


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Edit this bug report at https://bugs.php.net/bug.php?id=79356&edit=1


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