[sdcc-devel] [ sdcc-Bugs-3531687 ] Comparisons between bool and char broken

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Bugs item #3531687, was opened at 2012-06-03 10:16
Message generated for change (Comment added) made by mz-fuzzy
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 8
Private: No
Submitted By: Martin Matyas (mz-fuzzy)
Assigned to: Nobody/Anonymous (nobody)
Summary: Comparisons between bool and char broken

Initial Comment:
Sdcc generates wrong code for condition with conditional operator.

see sdccerr.lst:
- result of rows 57-61 is: acc is set if param a is nonzero. Then, on 62-65, acc is compared with result of conditional expression. This works wrong for flag=1 and a>1.
===================
int f(char a, char flag)
{
        if (a == (flag ? 1 : 0))
                return 0;
        return 1;
}
===================


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Comment By: Martin Matyas (mz-fuzzy)
Date: 2012-06-04 04:28

Message:
Philip,

for me, it's strange that you are writing about evaluating of "(flag ? 1 :
0)" as bool. It should be evaluated as "1" or "0" - meaning integers,
shouldn't it? But I'm not a compiler expert, just from a logical point of
view.

Martin

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Comment By: Philipp Klaus Krause (spth)
Date: 2012-06-04 03:17

Message:
This is even more serious:

1) The bug is not z80-specific, it affects all ports.
2) It affects all comparisons (equality, less-than, etc) between char (both
signed and unsigned) and bool.

In all these cases the char operand is cast to bool before comparing.

In your case we have the comparison == between the char a and the bool
(flag ? 1 : 0) resulting in a being cast to boolbefore the comparison.

Philipp


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Comment By: Martin Matyas (mz-fuzzy)
Date: 2012-06-03 10:18

Message:
... sorry, forgot to add:
SDCC :
mcs51/gbz80/z80/z180/r2k/r3ka/ds390/pic16/pic14/TININative/ds400/hc08/s08
3.1.5 #7827 (Jun  1 2012) (Linux)
command line:
sdcc -mz80 -c sdccerr.c

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Comment By: Martin Matyas (mz-fuzzy)
Date: 2012-06-03 10:16

Message:
prio 7 as a wrong code is generated silently

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