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c++/9207: GCC3.2 arm prolog stack frame use before allocation with -Os

>Number:         9207
>Category:       c++
>Synopsis:       GCC3.2 arm prolog stack frame use before allocation with -Os
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jan 06 14:56:01 PST 2003
>Closed-Date:
>Last-Modified:
>Originator:     raymund hofmann
>Release:        gcc3.2
>Organization:
>Environment:
cygwin on 686 W2000 Machine
gcc3.2 built on it
>Description:
compiling the source with -Os gives a non interrupt-safe prolog like:

	.file	"topolino_bug.cpp"
	.text
	.align	2
	.global	_ZN10CMoveFrame4drawEb
	.type	_ZN10CMoveFrame4drawEb,function
_ZN10CMoveFrame4drawEb:
	@ args = 0, pretend = 0, frame = 68
	@ frame_needed = 1, uses_anonymous_args = 0
	mov	ip, sp
	stmfd	sp!, {r4, r5, r6, r7, r8, r9, sl, fp, ip, lr, pc}
	sub	fp, ip, #4
	str	r0, [fp, #-84]   *** store this * before
	sub	sp, sp, #72      *** stack is allocated
        ...
        ...

thus a IRQ/FIQ which stores data on the Stack on which this code is running can corrupt the data which was stored on the stack ("str	r0, [fp, #-84]") before the allocation ("sub sp, sp, #72").

Compiling without -Os gives a correct prolog first allocating and then using the stack frame.


>How-To-Repeat:
run 'bug.sh' on bash
>Fix:
workaround -mno-sched-prolog
>Release-Note:
>Audit-Trail:
>Unformatted:
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