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Bug #80857 Big endian issue with functions returning 32-bit integers on 64-bit OS
Submitted: 2021-03-12 22:19 UTC Modified: 2021-09-16 21:26 UTC
From: calvin at cmpct dot info Assigned:
Status: Open Package: FFI (PECL)
PHP Version: 8.0.3 OS: IBM i 7.2
Private report: No CVE-ID: None
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From: calvin at cmpct dot info
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 [2021-03-12 22:19 UTC] calvin at cmpct dot info
Description:
------------
On a big endian system (in my case, IBM i PASE), the FFI extension, at least for 32-bit integers returned (but likely other types/mechanisms as well from a skimming of the source), will return 0. This is seemingly because the result is stored in a 64-bit word, but FFI accesses it as if it was a 32-bit value. This works on little-endian, but returns the empty part of the word on big-endian.

The actual result is from an IBM i PASE system (ppc64be), while the expected result is from an amd64 Fedora system.

Test script:
---------------
// ffi.c (gcc -o ffi.so (-maix64) -shared ffi.c)

long long problem(void)
{
        return 0x1122334455667788;
}
int problem32(void)
{
        return 0x11223344;
}

// ffi3.php

<?php

$ffi = FFI::cdef("long long problem(); int problem32();", "./ffi.so");
echo dechex($ffi->problem()) . "\n";
echo dechex($ffi->problem32()) . "\n";


Expected result:
----------------
1122334455667788
11223344


Actual result:
--------------
1122334455667788
0


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 [2021-09-16 21:26 UTC] cmb@php.net
-Package: ffi +Package: FFI
 
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