Re: sizeof evaluates expression to compute size?

On Wed, Sep 16, 2015 at 07:56:32AM -0700, Joel Brobecker wrote:
> >   Is it true that gdb evaluates the expression in a "print
> >   sizeof(expression)" to figure out the size?
> 
> Yes; it actually evaluates the entire expression (including the use
> of the sizeof operator).
> 
> >   For one expression on the ARM target 
> > 
> >      print sizeof((char*)(s->m)
> 
> The expression is incomplete; but with the expression you gave and
> assuming we're just missing a closing parenthesis, I don't see why
> it would need to allocate memory in the inferior. Perhaps you've found
> a bug.

Here's a more complete testcase.

typedef struct tagFoo
{
    int x;
    char arr[10];
} Foo;

Foo *pFoo;
int main()
{
  return 1;
}

Compiling with
$ gcc test.c -O0 -g3

and then starting gdb (native x86_64, v7.10) gives
$ gdb a.out
>>> print sizeof((char*)pFoo->arr) 
evaluation of this expression requires the target program to be active

Starting the program, putting a breakpoint on malloc, and then executing
the above command  causes the breakpoint to be hit.

Evaluation works fine without the cast to char*
>>> print sizeof(pFoo->arr)
$2 = 10

Should I file a bug?

Regards
Senthil