🚀 go-pugleaf

	Several people have asked to see my minimal code example
for the Manx assembler bug.  Here is a shar file containing
lots of information, including the letters I wrote to Manx and
(long ago) to the Net.  I hope this posting is not too big.
Enjoy!

	It's probably best to read the two "letter" files to understand
what the rest of the files here are.  Basically, I have enclosed 2
programs called "good" and "bad".  "good" compiles and assembles, but
"bad" does not. The difference between good.c and bad.c is only 1
character.

	Enclosed are the 2 C files, the result of running "diff" on the
files, the assembler output from the 2 C files, the "diff" of the
assembler files, and my letters to Manx and to the Net.

Enjoy!

Dan Barrett	ins_adjb@jhunix.UUCP			UUCP
		barrett@cs.jhu.edu	(128.220.13.4)	ARPA
Dept. of Computer Science, Johns Hopkins University, Baltimore, MD  21218

# This is a shell archive.  Remove anything before this line,
# then unpack it by saving it in a file and typing "sh file".
#
# Wrapped by crabcake!barrett on Wed Oct  5 00:14:11 EDT 1988
# Contents:  asm.diffs bad.asm bad.c c.diffs error.message good.asm good.c
#	letter net.letter
 
echo x - asm.diffs
sed 's/^@//' > "asm.diffs" <<'@//E*O*F asm.diffs//'
THIS IS THE OUTPUT OF "DIFF BAD.ASM GOOD.ASM"
*********************************************

44c44
< ;		case 'x':	/* Change 'x' to ANY other character from   */
---
> ;		case 'y':	/* Change 'x' to ANY other character from   */
131a132
> 	dc.w	.29-.31-2
135,138c136,140
< 	cmp.l	#55,d0
< 	bcc	.29
< 	asl.l	#1,d0
< 	move.w	.30(pc,d0.w),d0
---
> 	cmp.l	#56,d0
> 	bcc	.29
> 	asl.l	#1,d0
> 	lea	.30,a0
> 	move.w	(a0,d0.w),d0
@//E*O*F asm.diffs//
chmod u=rw,g=r,o=r asm.diffs
 
echo x - bad.asm
sed 's/^@//' > "bad.asm" <<'@//E*O*F bad.asm//'
;:ts=8
;main()
;{
	public	_main
_main:
	link	a5,#.2
	movem.l	.3,-(sp)
;	char p;
;
;	p = 'g';
	move.b	#103,-1(a5)
;
;	switch(p) {
	move.b	-1(a5),d0
	ext.w	d0
	ext.l	d0
	bra	.4
;		case 'a':
@.6
;		case 'b':
@.7
;		case 'c':
@.8
;		case 'd':
@.9
;		case 'e': 
@.10
;		case 'f':
@.11
;		case 'g':
@.12
;		case 'h':
@.13
;		case 'i':
@.14
;		case 'j':
@.15
;		case 'k':
@.16
;		case 'l':
@.17
;		case 'm':
@.18
;		case 'x':	/* Change 'x' to ANY other character from   */
@.19
;				/* 'n' to 'z', or possibly others, and this */
;				/* compiles and assembles without error.    */
;		case 'B':	
@.20
;		case 'D':
@.21
;		case 'F':
@.22
;		case 'H':
@.23
;		case 'I':
@.24
;		case 'L':
@.25
;		case 'O':
@.26
;		case 'P':
@.27
;		case 'X':
@.28
;			break;
	bra	.5
;		default:
@.29
;			puts("foo");
	pea	.1+0
	jsr	_puts
	add.w	#4,sp
;			break;
	bra	.5
;	}
@.30
	dc.w	.20-.31-2
	dc.w	.29-.31-2
	dc.w	.21-.31-2
	dc.w	.29-.31-2
	dc.w	.22-.31-2
	dc.w	.29-.31-2
	dc.w	.23-.31-2
	dc.w	.24-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.25-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.26-.31-2
	dc.w	.27-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.28-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.6-.31-2
	dc.w	.7-.31-2
	dc.w	.8-.31-2
	dc.w	.9-.31-2
	dc.w	.10-.31-2
	dc.w	.11-.31-2
	dc.w	.12-.31-2
	dc.w	.13-.31-2
	dc.w	.14-.31-2
	dc.w	.15-.31-2
	dc.w	.16-.31-2
	dc.w	.17-.31-2
	dc.w	.18-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.19-.31-2
@.4
	sub.l	#66,d0
	cmp.l	#55,d0
	bcc	.29
	asl.l	#1,d0
	move.w	.30(pc,d0.w),d0
@.31
	jmp	(pc,d0.w)
@.5
;}
@.32
	movem.l	(sp)+,.3
	unlk	a5
	rts
@.2	equ	-2
@.3	reg	
@.1
	dc.b	102,111,111,0
	ds	0
	public	_puts
	public	.begin
	dseg
	end
@//E*O*F bad.asm//
chmod u=rw,g=r,o=r bad.asm
 
echo x - bad.c
sed 's/^@//' > "bad.c" <<'@//E*O*F bad.c//'
main()
{
	char p;

	p = 'g';

	switch(p) {
		case 'a':
		case 'b':
		case 'c':
		case 'd':
		case 'e': 
		case 'f':
		case 'g':
		case 'h':
		case 'i':
		case 'j':
		case 'k':
		case 'l':
		case 'm':
		case 'x':	/* Change 'x' to ANY other character from   */
				/* 'n' to 'z', or possibly others, and this */
				/* compiles and assembles without error.    */
		case 'B':	
		case 'D':
		case 'F':
		case 'H':
		case 'I':
		case 'L':
		case 'O':
		case 'P':
		case 'X':
			break;
		default:
			puts("foo");
			break;
	}
}
@//E*O*F bad.c//
chmod u=rw,g=r,o=r bad.c
 
echo x - c.diffs
sed 's/^@//' > "c.diffs" <<'@//E*O*F c.diffs//'
THIS IS THE OUTPUT OF "DIFF BAD.C GOOD.C".
******************************************

21c21
< 		case 'x':	/* Change 'x' to ANY other character from   */
---
> 		case 'y':	/* Change 'x' to ANY other character from   */
@//E*O*F c.diffs//
chmod u=rw,g=r,o=r c.diffs
 
echo x - error.message
sed 's/^@//' > "error.message" <<'@//E*O*F error.message//'
       move.w  .41(pc,d0.w),d0
                             ^
ram:ctmpA21.056: 784: ***ERROR - Pc relative out of byte range, -130.
1 errors
@//E*O*F error.message//
chmod u=rw,g=r,o=r error.message
 
echo x - good.asm
sed 's/^@//' > "good.asm" <<'@//E*O*F good.asm//'
;:ts=8
;main()
;{
	public	_main
_main:
	link	a5,#.2
	movem.l	.3,-(sp)
;	char p;
;
;	p = 'g';
	move.b	#103,-1(a5)
;
;	switch(p) {
	move.b	-1(a5),d0
	ext.w	d0
	ext.l	d0
	bra	.4
;		case 'a':
@.6
;		case 'b':
@.7
;		case 'c':
@.8
;		case 'd':
@.9
;		case 'e': 
@.10
;		case 'f':
@.11
;		case 'g':
@.12
;		case 'h':
@.13
;		case 'i':
@.14
;		case 'j':
@.15
;		case 'k':
@.16
;		case 'l':
@.17
;		case 'm':
@.18
;		case 'y':	/* Change 'x' to ANY other character from   */
@.19
;				/* 'n' to 'z', or possibly others, and this */
;				/* compiles and assembles without error.    */
;		case 'B':	
@.20
;		case 'D':
@.21
;		case 'F':
@.22
;		case 'H':
@.23
;		case 'I':
@.24
;		case 'L':
@.25
;		case 'O':
@.26
;		case 'P':
@.27
;		case 'X':
@.28
;			break;
	bra	.5
;		default:
@.29
;			puts("foo");
	pea	.1+0
	jsr	_puts
	add.w	#4,sp
;			break;
	bra	.5
;	}
@.30
	dc.w	.20-.31-2
	dc.w	.29-.31-2
	dc.w	.21-.31-2
	dc.w	.29-.31-2
	dc.w	.22-.31-2
	dc.w	.29-.31-2
	dc.w	.23-.31-2
	dc.w	.24-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.25-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.26-.31-2
	dc.w	.27-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.28-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.6-.31-2
	dc.w	.7-.31-2
	dc.w	.8-.31-2
	dc.w	.9-.31-2
	dc.w	.10-.31-2
	dc.w	.11-.31-2
	dc.w	.12-.31-2
	dc.w	.13-.31-2
	dc.w	.14-.31-2
	dc.w	.15-.31-2
	dc.w	.16-.31-2
	dc.w	.17-.31-2
	dc.w	.18-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.29-.31-2
	dc.w	.19-.31-2
@.4
	sub.l	#66,d0
	cmp.l	#56,d0
	bcc	.29
	asl.l	#1,d0
	lea	.30,a0
	move.w	(a0,d0.w),d0
@.31
	jmp	(pc,d0.w)
@.5
;}
@.32
	movem.l	(sp)+,.3
	unlk	a5
	rts
@.2	equ	-2
@.3	reg	
@.1
	dc.b	102,111,111,0
	ds	0
	public	_puts
	public	.begin
	dseg
	end
@//E*O*F good.asm//
chmod u=rw,g=r,o=r good.asm
 
echo x - good.c
sed 's/^@//' > "good.c" <<'@//E*O*F good.c//'
main()
{
	char p;

	p = 'g';

	switch(p) {
		case 'a':
		case 'b':
		case 'c':
		case 'd':
		case 'e': 
		case 'f':
		case 'g':
		case 'h':
		case 'i':
		case 'j':
		case 'k':
		case 'l':
		case 'm':
		case 'y':	/* Change 'x' to ANY other character from   */
				/* 'n' to 'z', or possibly others, and this */
				/* compiles and assembles without error.    */
		case 'B':	
		case 'D':
		case 'F':
		case 'H':
		case 'I':
		case 'L':
		case 'O':
		case 'P':
		case 'X':
			break;
		default:
			puts("foo");
			break;
	}
}
@//E*O*F good.c//
chmod u=rw,g=r,o=r good.c
 
echo x - letter
sed 's/^@//' > "letter" <<'@//E*O*F letter//'
@.ps 11
@.vs 12
@.sp 5
@.TS
expand center;
lp+3 rp-1
lp-1 rp-1.
\fBDANIEL J. BARRETT\fR	Home: (301) 889-3934
Computer Science Department, Johns Hopkins University, Baltimore, MD  21218	Work: (301) 338-7784
_
@.TE

@.ce 1
\fI\n(mo/\n(dy/\n(yr\fR




@.ps 12
@.vs 13
@.ad b
@.nh
@.nf
Manx Technical Support
\fIAttn: Dorothy\fR
@.fi

Dear Tech Support:

I have discovered a very strange bug in your Amiga C compiler, versions
3.4 and 3.6A.  This is 100% definitely a compiler bug and not a user
error. I discussed this bug on 3/1/88 with a very helpful tech person
named Dorothy.  I have now isolated the bug and herein provide a simple
program that generates it.

In the pages that follow, I have documented the bug extensively.  The
program \fBbad.c\fR demonstrates the bug, and the program \fBgood.c\fR
demonstrates a non-buggy version.  The difference between \fBgood.c\fR
and \fBbad.c\fR is only \fIone character!!\fR

Here is a summary of the bug.  \fBgood.c\fR compiles without error.  For
\fBbad.c\fR, however, the assembler flags the following line and refuses
to continue:

@.nf
@.in +5
       move.w  .30(pc,d0.w),d0

ram:ctmpA21.056: 784: ***ERROR - Pc relative out of byte range, -130.
1 errors

@.in -5
@.fi

\fBbad.c\fR contains the line \fIcase 'x':\fR, and \fBgood.c\fR has the
line \fIcase 'y':\fR instead.  This is the only difference between the
two programs.  Yet, one program compiles and the other doesn't!  I tried
compiling with all sorts of compiler options (particularly +P) but the
bug remains.  You will find the assembler output of the two programs
very interesting.

The rest of this letter includes the following:

@.nf
@.in +5
The source code for \fBbad.c\fR and \fBgood.c\fR;
The output of \fBdiff bad.c good.c\fR;
The output of \fBcc -AT bad.c\fR and \fBcc -AT good.c\fR;  (maybe +P too... I forget.)
The output of \fBdiff bad.asm good.asm\fR.
@.in -5
@.fi

I hope you find this useful!

@.in +28
@.nf
Sincerely,



Daniel J. Barrett
@//E*O*F letter//
chmod u=rw,g=r,o=r letter
 
echo x - net.letter
sed 's/^@//' > "net.letter" <<'@//E*O*F net.letter//'
	I have found a VERY VERY VERY weird bug in Manx 3.6A (and
earlier versions too).  I have reported it to Manx, and I thought
I'd describe it here.

	The following program fails to compile and assemble properly.
You get the error message:

       move.w  .30(pc,d0.w),d0
                             ^
ram:ctmpA21.056: 784: ***ERROR - Pc relative out of byte range, -130.
1 errors

However, if you make the small change described in the program, it
compiles fine.  The difference is only ONE CHARACTER CONSTANT!!!

The assembler output of the compiler, for the bad program and the
good program, differs in the following way.  (Output of the
"diff" program.)

44c44
< ;		case 'x':	/* Change 'x' to ANY other character from   */
---
> ;		case 'y':	/* Change 'x' to ANY other character from   */
131a132
> 	dc.w	.29-.31-2
135,138c136,140
< 	cmp.l	#55,d0
< 	bcc	.29
< 	asl.l	#1,d0
< 	move.w	.30(pc,d0.w),d0		<===THIS IS THE BAD INSTRUCTION
---
> 	cmp.l	#56,d0
> 	bcc	.29
> 	asl.l	#1,d0
> 	lea	.30,a0
> 	move.w	(a0,d0.w),d0

	Can anyone explain why this weird bug might happen??

--------------------------bad.c:  cut here---------------------------
main()
{
	char p;

	p = 'g';

	switch(p) {
		case 'a':
		case 'b':
		case 'c':
		case 'd':
		case 'e': 
		case 'f':
		case 'g':
		case 'h':
		case 'i':
		case 'j':
		case 'k':
		case 'l':
		case 'm':
		case 'x':	/* Change 'x' to ANY other character from   */
				/* 'n' to 'z', or possibly others, and this */
				/* compiles and assembles without error.    */
		case 'B':	
		case 'D':
		case 'F':
		case 'H':
		case 'I':
		case 'L':
		case 'O':
		case 'P':
		case 'X':
			break;
		default:
			puts("foo");
			break;
	}
}

@//E*O*F net.letter//
chmod u=rw,g=r,o=r net.letter
 
echo Inspecting for damage in transit...
temp=/tmp/shar$$; dtemp=/tmp/.shar$$
trap "rm -f $temp $dtemp; exit" 0 1 2 3 15
cat > $temp <<\!!!
      20      70     420 asm.diffs
     155     322    1929 bad.asm
      38      87     522 bad.c
       7      35     219 c.diffs
       4      16     141 error.message
     157     326    1954 good.asm
      38      87     522 good.c
      81     309    1944 letter
      79     269    1667 net.letter
     579    1521    9318 total
!!!
wc  asm.diffs bad.asm bad.c c.diffs error.message good.asm good.c letter net.letter | sed 's=[^ ]*/==' | diff -b $temp - >$dtemp
if [ -s $dtemp ]
then echo "Ouch [diff of wc output]:" ; cat $dtemp
else echo "No problems found."
fi
exit 0
-- 
Dan Barrett	ins_adjb@jhunix.UUCP			UUCP
		barrett@cs.jhu.edu	(128.220.13.4)	ARPA
Dept. of Computer Science, Johns Hopkins University, Baltimore, MD  21218