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From: cbramix AT libero DOT it (Carlo)
Newsgroups: comp.os.msdos.djgpp
Subject: problem with assembly constraints
Date: 19 Nov 2003 15:59:41 -0800
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Hello everyone,

I'm asking your help for solving a strange problem.
Let's take this code:

static void function_1(void)
{
	printf("function 1 called\n");
}

void function_2(void)
{
	asm (" jmp _function_1 ");
}

This is a very simple example about what I want to do.
At the end of function_2() I want to call function_1().
My optimization is:

	jmp function_1

instead of:

	call function_1
	ret

This is an optimization done by newer GCC versions too when it
compiles the source.
But for some reasons I must do it myself.
The real problem happens when the global optimizer find that
function_1() doesn't seem to be used, and since it's declared as
"static" it removes it!!!
And the final result is that function_1() is missing.
I haven't this problems with my old GCC 2.7.2.1, so I tried to do some
tests...

I changed to:

	asm (" jmp %0 " ::"i"(function_1) );

but without success, because GCC converts it to:

	jmp $_function_1

and the '$' character stops AS.EXE during assembling.
I'm weak about constraints usage, can you give me some suggestions for
correcting this line?

Sincerely,

Carlo