[sdcc-devel] [ sdcc-Bugs-892400 ] Assign to bit var doesnt always work

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Bugs item #892400, was opened at 2004-02-07 16:49
Message generated for change (Comment added) made by stsp
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=100599&aid=892400&group_id=599

Category: Icode generator
Group: fixed
Status: Closed
Resolution: Fixed
Priority: 5
Submitted By: Stas Sergeev (stsp)
Assigned to: Erik Petrich (epetrich)
Summary: Assign to bit var doesnt always work

Initial Comment:
Hi.

There is a bug which makes assigning to a bit var to
generate a wrong code sometimes.
Here is an example:
---
volatile bit a;
idata unsigned char b;
struct {
 unsigned char c;
} tst;

char main()
{
  a = b;
  a = tst.c;
  return a;
}
---

Generated asm looks like this:
---
;bit.c:9: a = b;
;     genAssign
	mov	r0,#_b
	mov	a,@r0
	add	a,#0xff
	mov	_a,c
[that's correct]

;bit.c:10: a = tst.c;
;     genPointerGet
;     genNearPointerGet
	mov	r0,#_tst
;     genUnpackBits
	mov	a,@r0
	anl	a,#0x01     <--- BUG!
	add	a,#0xff
	mov	_a,c
---

Test-case is attached.

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>Comment By: Stas Sergeev (stsp)
Date: 2004-02-09 20:58

Message:
Logged In: YES 
user_id=501371

Hi Erik.
I have tested your fix. Yes, it produces the correct code
now, yet very very suspicious. I cant help feeling there is
a bug or two still here.
Here is an example that keeps me worried:
---
struct {
unsigned char a;
unsigned char b;
} tst1;
struct {
unsigned char c;
} tst2;

bit b1, b2, b3;

char main() {
  b1 = tst1.b;
  b2 = tst1.b;
  b3 = tst2.c;
  return 0;
}
---

The generated asm looks like this:
---
;struct.c:12: b1 = tst1.b;
;     genAssign
;     genAssign
	mov	a,0x0001 + _tst1
	add	a,#0xff
	mov	_b1,c
[ perfectly correct ]

;struct.c:13: b2 = tst1.b;
;     genAssign
	mov	a,0x0001 + _tst1
	add	a,#0xff
	mov	_b2,c
[ perfectly correct ]

;struct.c:14: b3 = tst2.c;
;     genPointerGet
;     genNearPointerGet
	mov	r0,#_tst2
	mov	a,@r0
	add	a,#0xff
	mov	_b3,c
[ why is that??? ]
---

So yes, the code is correct... But what's the idea there
behind the indirection in the third fragment? Almost
certainly a bug...
(OKey, now I am calling a perfectly valid code a bug,
what's next? :)
Test case is attached.

As a side-note: if you change "tst2" to "tst1" in that
example, so that the symbol is duplicated, the error
message is not perfect:
---
struct.c:7: error: Duplicate symbol 'tst1', symbol IGNORED
from type 'struct __00010000'
to type 'struct __00010001'
---
Something cryptical here definitely.

----------------------------------------------------------------------

Comment By: Stas Sergeev (stsp)
Date: 2004-02-08 17:36

Message:
Logged In: YES 
user_id=501371

Thanks, good to see it fixed.
This bug "bugged" me exactly when I was demonstrating
my program to the boss. Fortunately, got used to the
fact that the bugs are to be looked up in a generated
asm rather than in a source code, I was able to identify
and work around the problem before his patience run out:)

----------------------------------------------------------------------

Comment By: Erik Petrich (epetrich)
Date: 2004-02-08 12:00

Message:
Logged In: YES 
user_id=635249

Fixed in all of the code generators that have a type "bit"
separate from bitfields: src/mcs51/gen.c 1.192,
src/ds390/gen.c 1.214, src/pic/gen.c 1.89, src/pic16/gen.c 1.19


----------------------------------------------------------------------

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