Re: [PATCH 2/2] [gdb] Fix rethrow exception slicing in insert_bp_location

[Pedro Alves <pedro@palves.net>]

On 2022-10-24 5:43 p.m., Tom de Vries wrote:
> On 10/24/22 18:36, Pedro Alves wrote:
>> On 2022-10-24 9:49 a.m., Tom de Vries via Gdb-patches wrote:
>>
>>> +#define RETHROW_ON_TARGET_CLOSE_ERROR(E)                \
>>> +  do                                    \
>>> +    {                                    \
>>> +      if ((E).reason != 0)                        \
>>> +    {                                \
>>> +      /* Can't set the breakpoint.  */                \
>>> +                                    \
>>> +      if ((E).error == TARGET_CLOSE_ERROR)                \
>>> +        /* If the target has closed then it will have deleted any    \
>>> +           breakpoints inserted within the target inferior, as a    \
>>> +           result any further attempts to interact with the        \
>>> +           breakpoint objects is not possible.  Just rethrow the    \
>>> +           error.  Don't use E to rethrow, to prevent object    \
>>> +           slicing of the exception.  */                \
>>> +        throw;                            \
>>> +    }                                \
>>> +    } while (0)
>>
>> Is there a reason this is a macro instead of a function?
> 
> yes, the throw without expression.
> 
> Do you know of a way to do this using a function?

WDYM?  I believe it should Just Work.  E.g.:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <stdio.h>

struct excpt
{
};

struct excpt2 : excpt
{
};

void
rethrow ()
{
  throw;
}

int main ()
{
  try
    {
      try
	{
	  throw excpt2{};
	}
      catch (const excpt &)
	{
	  rethrow ();
	}
    }
  catch (const excpt2 &)
    {
      printf ("caught excpt2\n");
    }
  return 0;
}

$ g++ test_rethrow.cc -o test_rethrow
$ ./test_rethrow
caught excpt2
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~