shafik added a comment.
In D85376#2209638 <https://reviews.llvm.org/D85376#2209638>, @labath wrote:
> This manifested itself for variables in registers because those end up being
> described as `eValueTypeScalar`, is that so?
>
> If that's the case, then I think this would also manifest for variables
> described via `DW_OP_constu 0xdead, DW_OP_stack_value`. And if *that* is
> true, then this could be tested a lot simpler by having a global variable
> described by DW_OP_stack_value and "target variable"-ing it -- no makefiles,
> no python, just a simple .s file. And it would run on all platforms, not just
> darwin.
>
> `test/Shell/SymbolFile/DWARF/DW_OP_piece-struct.s` tests a very similar thing
> in precisely this way. I suspect you could just take that test as a template
> and replace the struct definition with one that contains bitfieds.
This sounds like a great approach, I have unfortunately been struggling to get
a test case that works. It looks like I am hitting another bug, I am not
surprised b/c using slight variations on this code I have found other three
other bugs with how we deal with `DW_OP_piece`, `DW_OP_bit_piece` and I think
`DW_AT_const_value` respectively.
I have been working w/ this:
#include <stdio.h>
typedef union
{
unsigned raw;
struct
{
unsigned a : 8;
unsigned b : 8;
unsigned c : 6;
unsigned d : 2;
unsigned e : 6;
unsigned f : 2;
} ;
} U;
static U ug= (U)(unsigned)0x0;
void f(U u) {
printf( "%d\n", u.raw);
return;
}
int main() {
ug.raw = 0x64A40101;
f(ug);
printf( "%d\n", ug.raw);
}
and compiling as using `clang -O1 -gdwarf-4` but we obtain bad values:
(lldb) target variable ug
(U) ug = {
raw = 3395301392
= (a = 16, b = 48, c = 32, d = 1, e = 10, f = 3)
}
I tried generating assembly and manually adjusting the debug info but I was not
able to get very far there.
FYI this was the DWARF expression it was generating:
DW_AT_location (DW_OP_addr 0x100002010, DW_OP_deref_size 0x1,
DW_OP_constu 0x64a40101, DW_OP_mul, DW_OP_lit0, DW_OP_plus, DW_OP_stack_value)
If you can come up w/ a way to generate a test that produces correct values I
am happy to use it!
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