From:	Harald Jeszenszky <harald DOT jeszenszky AT oeaw DOT ac DOT at>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Arbitrary variable order ?
Date:	Thu, 06 Jul 2000 09:22:28 +0200
Organization:	Technische Universitaet Graz, Austria
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Message-ID:	<396433B4.4370ADC2@oeaw.ac.at>
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To:	djgpp AT delorie DOT com
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Hello,

I've ported a large program to DJGPP and I can compile and run it
without any problems. The program uses two variables (lets say
copy_start, and copy_end) for copying some data from memory to a buffer.
The variables are declared as follows:

	...
	int copy_start;
	int variable_1;
	...
	int variable_n;
	int copy_end;
	...

The statement

	memcpy(buffer, &copy_start, &copy_end - &copy_start - 1);

should copy the contents of variable_1 to variable_n to the buffer. This
works fine on the old platform but fails with DJGPP.

After comparing the map files it turned out that, on the old platform,
the varibles are having the same order in memory as they are declared.
In the DJGPP version the variables are stored in arbitrary order in 
memory !!! The address of the variable copy_end was less than the
address of the variable copy_start !!!

Is there a way to force the compiler to map the variables in memory in
the same order as they are declared?

Thanks in advance

Harald (harald DOT jeszenszky AT oeaw DOT ac DOT at)

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