Re: [Tinycc-devel] x86_64: second struct va_arg fails

[shinichiro hamaji]

On Thu, Dec 16, 2010 at 9:06 AM, Henry Kroll <address@hidden> wrote:
> On Wed, 2010-12-15 at 03:07 +0100, grischka wrote:
>> Henry Kroll wrote:
>> > x86_64 fails to copy the second struct passed to va_arg.
>> >
>> > static struct myspace {
>> >     short int profile;
>> > } bob = { 42 };
>> >
>> > void badfunc(int eek, ...) {
>> >     va_list ack;
>> >     int validate;
>> >     struct myspace george, bill;
>> >     va_start(ack, eek);
>> >         bill     = va_arg(ack, struct myspace);
>> >         george   = va_arg(ack, struct myspace);
>> >         validate = va_arg(ack, int);
>> > [...]
>> > int main(int argc, char **argv) {
>> >     badfunc(0, bob, bob, bob.profile);
>> > [...]
>>
>> This line from tcc's include/stdarg.h might give a hint:
>>      /* XXX: this lacks the support of aggregated types. */                  
>> \
>>
>> I have no idea though how such support would look like.
>>
>> Btw. on win64 it does not work either.  I must have misunderstood
>> something about the structures part of the calling conventions.
>>
>> --- grischka
>>
>>
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>
> This passes some hurried tests I threw at it, but I'm sure it needs more
> type checking. I used the attached test program to generate a map of
> ap->overflow_arg_area for various sized structures.

This is one of my TODO. I think the easiest way would be adding a
builtin function like __builtin_aggregate_types_p and using it in
stdarg.h. I hesitated to do this because any other compilers don't
have such extensions. A better way would be defining __builtin_va_arg
just like GCC. I guess I will have some spare time this year end. I'll
try working on this if no one don't fix.