[Bug exp/26519] New: wrong type used when printing value

[Bug exp/26519] New: wrong type used when printing value

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26519

            Bug ID: 26519
           Summary: wrong type used when printing value
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: exp
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Consider the following test-case:
...
$ cat test.c
struct ab
{
  int a;
  int b;
};

extern void bar (void *p);
extern void foo (struct ab *);

int
main (void)
{
  struct ab ab;
  struct { float a, b; } f = { 1.1, 2.1 };
  bar (&f);
  foo (&ab);
  return 0;
}
$ cat test2.c
struct ab;

void
foo (struct ab *p)
{
}
$ cat test3.c
struct ab;

extern void bar2(struct ab *);

void
bar (struct ab *p)
{
  bar2 (p);
}
$ cat test4.c
struct ab {
  float a;
  float b;
};

void
bar2 (struct ab *p)
{

}
...

Compiled like this:
...
$ gcc -g test.c test2.c test3.c test4.c
...

When we run to bar and print "*p"
...
$ gdb -batch -iex "set language c" a.out -ex "b bar" -ex run -ex "p *p"
Breakpoint 1 at 0x4004ef: file test3.c, line 8.

Breakpoint 1, bar (p=0x7fffffffdc00) at test3.c:8
8         bar2 (p);
$1 = {a = 1066192077, b = 1074161254}
...
we use the type struct ab from test.c to print *p, which is incorrect.

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[Bug exp/26519] wrong type used when printing value

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26519

Tom Tromey <tromey at sourceware dot org> changed:

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

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
I don't think gdb has any way to know which one to pick.
It guesses, but maybe it should error instead.

I think there's another bug about making

print * ('test4.c:struct ab' *) p

... work.

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[Bug exp/26519] wrong type used when printing value

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26519

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom Tromey from comment #1)
> I don't think gdb has any way to know which one to pick.

Agreed.

> It guesses, but maybe it should error instead.
> 

In case of C++, I think guessing is fine due to ODR.

But I think for C, we should indeed error.

Or perhaps, prompt to choose which variant (although you mentioned in PR25769
that you wanted to get rid of those prompts).

> I think there's another bug about making
> 
> print * ('test4.c:struct ab' *) p
> 
> ... work.

I see.  I found PR22718, perhaps that's the one you meant.

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