FYI: Struct packing in mmreg.h

Article View: borland.public.cppbuilder.multimedia

Article #1177

Back to borland.public.cppbuilder.multimedia Previous Next

#1177

From: Frank K.
Date: Mon, 27 Aug 2001 18:59

20 lines
1545 bytes

I recently upgraded to BCB 5. One project, which uses the ACM, no
longer functioned correctly after rebuilding in BCB 5.

I traced the problem to mmreg.h failure to invoke #pragma pack(1)
which packs structs on byte boundaries. Specifically, the WAVEFORMAT
structures for compressed formats, MPEGLAYER3WAVEFORMAT for example,
inserted two extra bytes at the boundary between the WAVEFORMATEX
member and the tag specific fields.

The line #if !defined( RC_INVOKED ) && defined( _MSC_VER ) at the top
of mmreg.h causes the problem. Since _MSC_VER is not defined by BCB
#pragma pack(1) is never invoked.

Simply adding

#ifndef _MSC_VER
#define _MSC_VER 1020
#endif

to the top of mmreg.h solves the problem.

Technical Details

Message-ID: <3b8a9884.15186507@forums.inprise.com>

Path:

arc1-ca.pugleaf.net!archiver1.google.com!newsfeed.google.com!sn-xit-02!supernews.com!newsfeed.direct.ca!look.ca!xmission!news-hog.berkeley.edu!ucberkeley!nntp-relay.ihug.net!newsfeeds.ihug.co.nz!ihug.co.nz!dnews

Show Full Headers

Complete Article Headers

X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 10d0fc,455c920401c8dfea,start
X-Google-Attributes: gid10d0fc,public
X-Google-ArrivalTime: 2001-08-27 12:07:08 PST
From: Frank K.
Newsgroups: borland.public.cppbuilder.multimedia
Subject: FYI: Struct packing in mmreg.h
Date: Mon, 27 Aug 2001 18:59:54 GMT
Message-ID: <3b8a9884.15186507@forums.inprise.com>
X-Newsreader: Forte Agent 1.5/32.451
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
NNTP-Posting-Host: 24.116.70.142
X-Trace: dnews 998938711 24.116.70.142 (27 Aug 2001 11:58:31 -0700)
Lines: 22
Path: arc1-ca.pugleaf.net!archiver1.google.com!newsfeed.google.com!sn-xit-02!supernews.com!newsfeed.direct.ca!look.ca!xmission!news-hog.berkeley.edu!ucberkeley!nntp-relay.ihug.net!newsfeeds.ihug.co.nz!ihug.co.nz!dnews