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From: jeffm@suse.com To: gcc-gnats@gcc.gnu.org Subject: c/2894: Incorrect union padding on Linux/ARM port; other architectures correct Date: Mon, 21 May 2001 22:26:00 -0000 [thread overview] Message-ID: <20010522052115.2476.qmail@sourceware.cygnus.com> (raw) >Number: 2894 >Category: c >Synopsis: Incorrect union padding on Linux/ARM port; other architectures correct >Confidential: no >Severity: serious >Priority: high >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Mon May 21 22:26:00 PDT 2001 >Closed-Date: >Last-Modified: >Originator: Jeff Mahoney <jeffm@suse.com> >Release: gcc version 2.95.2; gcc version 2.95.4 20010319 (Debian prerelease); gcc version 3.1 20010512 (experimental) (from netwinder.org) >Organization: >Environment: Debian Linux [stable] Intel StrongARM-1110 rev 6 (v4l) Compaq iPAQ >Description: Incorrect union padding is produced on the Linux/ARM port. It seems that the alignment padding corrections are applied too early, so the size of the structure is incorrectly calculated, thus a structure is sized too large. This problem is surfacing in running ReiserFS on Linux/ARM, where incorrect sizes/offsets for on-disk structures are being generated. Linux/PPC, Linux/Intel, Solaris/Sparc, and Tru64/Alpha ports produce correct sizes/offsets. A simplified test case is attached. See PR #2547 for somewhat related info. >How-To-Repeat: #include <stdio.h> #include <linux/types.h> struct test2 { __u32 v1; __u32 v2; __u64 v3; __u16 v4_5; __u16 v6; __u32 v7; } __attribute__ ((__packed__)); struct test { __u32 v1; __u32 v2; __u64 v3; union { __u16 v4; __u16 v5; } u; __u16 v6; __u32 v7; } __attribute__ ((__packed__)); int main( void ) { printf( "sizeof( struct test ) = %d\n", sizeof( struct test ) ); printf( "sizeof( struct test2 ) = %d\n", sizeof( struct test2 ) ); } Output for ARM: sizeof( struct test ) = 26 sizeof( struct test2 ) = 24 (without __attribute__ ((__packed__)), sizeof( struct test ) = 28) Output for other tested arches (see desc. for list): sizeof( struct test ) = 24 sizeof( struct test2 ) = 24 (results are the same without __attribute__ ((__packed__)) ) >Fix: >Release-Note: >Audit-Trail: >Unformatted:
next reply other threads:[~2001-05-21 22:26 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2001-05-21 22:26 jeffm [this message] 2001-05-21 22:56 Neil Booth
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