Re: [PATCH] gdb/testsuite: Fix typos in infcall-nested-structs.c

Tom de Vries
2019-10-10T20:26:41Z

On 10-10-2019 20:30, Tom de Vries wrote:
> On 10-10-2019 19:24, Andreas Arnez wrote:
>> On Thu, Oct 10 2019, Tom de Vries wrote:
>>
>>> I see these new failures on x86_64-linux:
>>> ...
>>> FAIL: gdb.base/infcall-nested-structs.exp: l=c++: types-tc-tf: p/d
>>> check_arg_struct_02_01 (ref_val_struct_02_01)
>>> FAIL: gdb.base/infcall-nested-structs.exp: l=c++: types-ts-tf: p/d
>>> check_arg_struct_02_01 (ref_val_struct_02_01)
>>> FAIL: gdb.base/infcall-nested-structs.exp: l=c++: types-ti-tf: p/d
>>> check_arg_struct_02_01 (ref_val_struct_02_01)
>>> ...
>>
>> Maybe the test case caught a real bug then, right? Or do you see a
>> problem with the test case?
>
> I think it's a real bug.
>
> I've minimized the types-ti-tf FAIL to:
> ...
> $ cat test.c
> typedef int ti;
> typedef float tf;
> struct struct_02_01
> {
> struct { } es1;
> struct {
> struct {
> ti a;
> tf b;
> } s1;
> } s2;
> };
>
> struct struct_02_01 ref_val_struct_02_01 = {
> {},
> {
> {
> 'a',
> 'b'
> }
> }
> };
>
> int cmp_struct_02_01 (struct struct_02_01 a, struct struct_02_01 b)
> { return a.s2.s1.a == b.s2.s1.a && a.s2.s1.b == b.s2.s1.b; }
>
> int
> check_arg_struct_02_01 (struct struct_02_01 arg) {
> return cmp_struct_02_01 (arg, ref_val_struct_02_01);
> }
>
> int
> main (void)
> {
> return check_arg_struct_02_01 (ref_val_struct_02_01);
> }
> $ g++ test.c -g
> $ ./a.out; echo $?
> 1
> $ gdb a.out -batch -ex start -ex "p check_arg_struct_02_01
> (ref_val_struct_02_01)"
> Temporary breakpoint 1 at 0x400563: file test.c, line 35.
>
> Temporary breakpoint 1, main () at test.c:35
> 35 return check_arg_struct_02_01 (ref_val_struct_02_01);
> $1 = 0
> ...
>

The discrepancy is that the code generated by gcc passes the struct in
registers %rdi and %xmm0, but amd64_push_arguments classifies the struct as:
...
(gdb) p theclass
$57 = {AMD64_INTEGER, AMD64_INTEGER}
...
and therefore passes it in %rdi and %rsi.

Thanks,
- Tom