Re: Newlib 1.8.1 vfprintf problem on embedded PowerPC

[Roger Williams <roger@coelacanth.com>]

>>>>> Scott Howard <scott@objsw.com> writes:

  > Printf works fine, but the startup code supplied with newlib (see
  > libgloss/rs6000/*crt0.S) doesn't clear memory in the 'sbss'
  > section to all zeros, it only clears the 'bss' section. This is
  > what's sending printf etc. into the weeds.

Well, that would certainly do it.  But this is what my crt0.S looks
like -- it certainly appears to clear sbss:

	/* clear bss and sbss */
	lwz	r6,.Lbss_start(r5)	/* calculate beginning of the BSS */
	lwz	r7,.Lend(r5)		/* calculate end of the BSS */
	add	r6,r6,r4		/* adjust pointers */
	add	r7,r7,r4

	cmplw	1,r6,r7
	bc	4,4,.Ldone1

	subf	r8,r6,r7		/* number of bytes to zero */
	srwi	r9,r8,2			/* number of words to zero */
	mtctr	r9
	li	r0,0			/* zero to clear memory */
	addi	r6,r6,-4		/* adjust so we can use stwu */
.Lloop:
	stwu	r0,4(r6)		/* zero bss */
	bdnz	.Lloop

.Ldone1:

	lwz	r6,.Lsbss_start(r5)	/* calculate beginning of the SBSS */
	lwz	r7,.Lsbss_end(r5)	/* calculate end of the SBSS */
	add	r6,r6,r4		/* adjust pointers */
	add	r7,r7,r4

	cmplw	1,r6,r7
	bc	4,4,.Ldone

	subf	r8,r6,r7		/* number of bytes to zero */
	srwi	r9,r8,2			/* number of words to zero */
	mtctr	r9
	li	r0,0			/* zero to clear memory */
	addi	r6,r6,-4		/* adjust so we can use stwu */
.Lloop2:
	stwu	r0,4(r6)		/* zero bss */
	bdnz	.Lloop2

.Ldone:

My map file shows

                0x0002c464                PROVIDE (__sbss_start, .)
                0x0002c46c                PROVIDE (__sbss_end, .)
                0x0002c470                PROVIDE (__bss_start, .)
                0x0002c498                PROVIDE (end, .)

which seems about right for my test code.  Do you see a bug?

-- 
Roger Williams                         finger me for my PGP public key
Coelacanth Engineering Inc    consulting & turnkey product development
Middleborough, Massachusetts           wireless * datacomm * DSP * ATE
tel +1 508 947-5585 * fax +1 508 861-0278 * http://www.coelacanth.com/
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