FYI: Struct packing in mmreg.h

Thread View: borland.public.cppbuilder.multimedia

1 messages

[T] Back to Threads [V] Tree View [G] Group Articles

1 total messages Started by Frank K. Mon, 27 Aug 2001 18:59

#1177

Author: 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.

Thread Navigation

This is a paginated view of messages in the thread with full content displayed inline.

Messages are displayed in chronological order, with the original post highlighted in green.

Use pagination controls to navigate through all messages in large threads.

Back to All Threads