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From: ham@Neon.Stanford.EDU (Peter R. Ham)
Newsgroups: comp.sys.mips
Subject: Can some one explain this compiler output?
Message-ID: <HAM.89Nov11161238@Neon.Stanford.EDU>
Date: 12 Nov 89 00:12:38 GMT
Sender: USENET News System <news@Neon.Stanford.EDU>
Distribution: comp
Organization: Stanford University
Lines: 49

Question: Why does cc allocate 24 bytes of stack for a non-leaf procedure
with no local variables when calling another procedure that accepts no
arguments?

Given this C code:

extern void bar();

void
foo()
{
  bar();
}

cc produces:

	.verstamp	1 31
	.text	
	.align	2
	.file	2 "test.c"
	.globl	foo
	.loc	2 6
 #   1	
 #   2	extern void bar();
 #   3	
 #   4	void
 #   5	foo()
 #   6	{
	.ent	foo 2
foo:
	.option	O2
	subu	$sp, 24
	sw	$31, 20($sp)
	.mask	0x80000000, -4
	.frame	$sp, 24, $31
	.loc	2 7
 #   7	  bar();
	jal	bar
	.loc	2 8
 #   8	}
	lw	$31, 20($sp)
	addu	$sp, 24
	j	$31
	.end	foo

--
Peter Ham			PO Box 3430	(h)(415) 322-4390
MS Computer Science Student	Stanford, CA	ham@cs.stanford.edu
Stanford University 		94309		(o)(415) 723-2067