[Bug gdb/30345] New: GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[Bug gdb/30345] New: GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[hluaw at connect dot ust.hk]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

            Bug ID: 30345
           Summary: GDB shows "That operation is not available on integers
                    of more than 8 bytes." when printing regular
                    variables.
           Product: gdb
           Version: 13.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: hluaw at connect dot ust.hk
  Target Milestone: ---

Given the following code:
#pragma pack(1)
struct {
  unsigned : 6;
  signed : 8;
  signed : 27;
  signed : 6;
  unsigned b : 14;
  signed : 4;
} c, d;
int d_1, e, f, k, aa, l, af, ag, ah, h, iab, i_5;
long m;

int main() {
  int l_212;
  int *r[42] = {&e, &l_212, &f, &e, &f, &f, &l_212, &e, &f, &l_212, &f};
  l_212 = (m = (d.b |= 0) | 0);
}

Compiled with Clang 15.0.7 with -O1 -g.

l_212 is then with the following DWARF information:
  Range 0x55555555461d-0x555555554628: a complex DWARF expression:
     0: DW_OP_breg0 0 [$rax]
     2: DW_OP_constu 4294967295
     8: DW_OP_and
     9: DW_OP_convert<DW_ATE_unsigned_72 [0x27]>
    14: DW_OP_convert<DW_ATE_unsigned_32 [0x2b]>
    19: DW_OP_stack_value
    [4-byte piece]
.

Break at 0x55555555461d where this DWARF expression takes effect:
(gdb) b *0x55555555461d
Breakpoint 1 at 0x55555555461d
(gdb) r
Starting program: /home/hluaw/debugger-bugs/unavail_op/a.out

Breakpoint 1, 0x000055555555461d in main () at r.c:16
16        l_212 = (m = (d.b |= 0) | 0);
(gdb) p l_212
That operation is not available on integers of more than 8 bytes.

To my understanding, this error message should only appear when using something
like print ((int128_t)1) << 64

It seems not right to yield this error when evaluating a normal variable.

-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug gdb/30345] GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |26909
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
This sequence:
     9: DW_OP_convert<DW_ATE_unsigned_72 [0x27]>
    14: DW_OP_convert<DW_ATE_unsigned_32 [0x2b]>

...probably is the problem, and is also somewhat pointless.
Arguably perhaps the GMP support should be extended into DWARF
expressions, but at the same time, doing it just to support
this kind of thing seems like a lot of work for little benefit.


Referenced Bugs:

https://sourceware.org/bugzilla/show_bug.cgi?id=26909
[Bug 26909] [meta] Debug Clang-built code
-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug gdb/30345] GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[hluaw at connect dot ust.hk]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

--- Comment #2 from LU Hongyi <hluaw at connect dot ust.hk> ---
(In reply to Tom Tromey from comment #1)
> This sequence:
>      9: DW_OP_convert<DW_ATE_unsigned_72 [0x27]>
>     14: DW_OP_convert<DW_ATE_unsigned_32 [0x2b]>
> 
> ...probably is the problem, and is also somewhat pointless.
> Arguably perhaps the GMP support should be extended into DWARF
> expressions, but at the same time, doing it just to support
> this kind of thing seems like a lot of work for little benefit.

GDB seems to have a loose support for DW_OP_convert?

Another bug #30319 I found also relates to this operator, which reports Type
Incompatible when it (actually?) compatible.

-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug gdb/30345] GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

--- Comment #3 from Tom Tromey <tromey at sourceware dot org> ---
(In reply to LU Hongyi from comment #2)

> GDB seems to have a loose support for DW_OP_convert?

It's more that gdb supports 64 bit types in DWARF expressions,
but nothing wider.  This is done primarily because, until
this bug report, nobody ever saw a wider type in a DWARF
expression.

> Another bug #30319 I found also relates to this operator, which reports Type
> Incompatible when it (actually?) compatible.

I've commented on that one now.

-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug gdb/30345] GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

--- Comment #4 from Tom Tromey <tromey at sourceware dot org> ---
Ah, I forgot that when implementing DW_OP_convert,
we converted the DWARF expression evaluator to be value-based.
With that and the work to make 128-bit values work, 
I think this may be fixed on git master.

I can't try it though as my clang emits different DWARF:

     0: DW_OP_breg0 0 [$rax]
     2: DW_OP_constu 4294967295
     8: DW_OP_and
     9: DW_OP_stack_value
    10: DW_OP_piece 4 (bytes)

Anyway this is probably a dup of bug# 30190.
Could you try your example with git master gdb?

-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug gdb/30345] GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[hluaw at connect dot ust.hk]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

LU Hongyi <hluaw at connect dot ust.hk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #5 from LU Hongyi <hluaw at connect dot ust.hk> ---
I tried master gdb, it works now.

-- 
You are receiving this mail because:
You are on the CC list for the bug.

[Bug gdb/30345] GDB shows "That operation is not available on integers of more than 8 bytes." when printing regular variables.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30345

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.1

-- 
You are receiving this mail because:
You are on the CC list for the bug.