Hi TCC-fans,
Think I found a bug in the implementation of _Bool in return values in version
0.9.27, found on i386, probably applies to x86_64, and possibly others as well:
Since sizeof(_Bool) == 1 as implemented in TCC, I believe this comment in
i386-gen.c applies:
"extend the return value to the whole register if necessary
visual studio and gcc do not always set the whole eax register
when assigning the return value of a function"
The scenario that broke for me was calling a function that only set the AL
register on return, leaving the rest of EAX undefined, yet TCC checked the
whole of EAX for the _Bool return value (true came out correct, but false
tested as true when the undefined-bits were non-0)
Assigning the _Bool return value to a _Bool variable and then checking that
variable instead of the return value is one confirmed workaround (the emitted
TCC code then uses just AL to generate a full EAX before checking EAX), but I
think I have found the proper fix:
Add "case VT_BOOL:" as shown here, just after line 365 of i386-gen.c:
switch (rt & VT_BTYPE) {
case VT_BYTE:
case VT_BOOL:
This modification fixed the problem I was having, I *think* the line in
x86_64-gen.c that needs to change for the equivalent there is this (@ line 934):
else if (bt == VT_BYTE || bt == VT_BOOL)
Sorry, I don't know the other architectures or TCC in general well enough to
comment on other places that may also need this fix.
Best regards,
Louis
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