Re: make #pragma pack() implementation consistent with other compilers(PR c/7054)

["Joseph S. Myers" <jsm at polyomino dot org dot uk>]

On Wed, 7 Jul 2004, Jan Beulich wrote:

> 2004-07-07 Jan Beulich <jbeulich@novell.com>
> 
> 	PR c/7054
> 	* tree.h (initial_max_fld_align): Declare
> 	* stor-layout.c (initial_max_fld_align): Define and initialize.
> 	(maximum_field_alignment): Initialize to the same value.
> 	* common.opt: Add -fpack-struct= variant of switch.
> 	* opts.c: Handle -fpack-struct= variant of switch.
> 	* c-pragma.c: Change #pragma pack() handling so that is becomes
> 	compatible to other compilers: accept individual 'push'
> argument,
> 	make final pop restore (command line) default, correct
> interaction
> 	of push/pop and sole specification of a new alignment (so that
> the
> 	sequence #pragma pack(push) - #pragma pack(<n>) becomes
> identical
> 	to #pragma pack(push, <n>).
> 	* testsuite/gcc.dg/pack-test-2.c: Adjust to permit and check
> 	#pragma pack(push).

We can't consider patches without proper documentation.  This needs (a)  
documentation for the new command-line option syntax, (b) documentation
for the pragma changes (and it seems for the pragma itself, which as you
evidently understand what it's meant to do at present you're best placed
to write), (c) for what seems to be a new target macro
DEFAULT_PACK_STRUCT.

> /home/jbeulich/src/gcc/mainline/2004-07-05.10.09/gcc/testsuite/g++.dg/abi/vbase10.C	2004-01-08
> 04:32:11.000000000 +0100
> +++
> 2004-07-05.10.09/gcc/testsuite/g++.dg/abi/vbase10.C	2004-05-27
> 10:57:09.000000000 +0200

Not mentioned in the ChangeLog entry.  Why is this testcase being changed?

> /home/jbeulich/src/gcc/mainline/2004-07-05.10.09/gcc/testsuite/gcc.dg/Wpadded.c	2003-06-10
> 01:04:50.000000000 +0200
> +++ 2004-07-05.10.09/gcc/testsuite/gcc.dg/Wpadded.c	2004-05-26
> 15:38:24.000000000 +0200

Likewise.

> /home/jbeulich/src/gcc/mainline/2004-07-05.10.09/gcc/testsuite/gcc.dg/c99-flex-array-4.c	2002-08-17
> 16:48:28.000000000 +0200
> +++
> 2004-07-05.10.09/gcc/testsuite/gcc.dg/c99-flex-array-4.c	2004-05-26
> 17:19:15.000000000 +0200

Likewise.  It seems clearly inappropriate for standards testcases to have
any special options like you're adding.  (But this testcase is expected to
become obsolete, as the draft C99 TC2 (N1060) would remove the defective
requirement from the standard.)

-- 
Joseph S. Myers               http://www.srcf.ucam.org/~jsm28/gcc/
    jsm@polyomino.org.uk (personal mail)
    jsm28@gcc.gnu.org (Bugzilla assignments and CCs)