Re: Program terminated with SIGSEGV when trying to print an array element

Wu Zhou
2005-06-08T06:57:23Z

On Tue, 7 Jun 2005, Daniel Jacobowitz wrote:

> On Tue, Jun 07, 2005 at 04:58:10PM +0800, Wu Zhou wrote:
> > As far as I can see, the problem lies in that GDB take TYPE_CODE_PTR as
> > a function call as well. But in the above failing testcase, "a" is a
> > pointer to array type (Fortran treat formal parameter as pointer). Its
> > code is TYPE_CODE_PTR indeed, but it is not a function call.
> >
> > So maybe we need to change the code logic above. My thought is when the
> > code match TYPE_CODE_PTR, we first get its target_type. If it is
> > TYPE_CODE_ARRAY, we can goto multi_f77_subscript. If not, we can go on
> > with the orignial path. But I have one question on the original code:
> > in which circumstance should a function's code return TYPE_CODE_PTR,
> > isn't the code of a function always return TYPE_CODE_FUNC?
> >
> > Any thought on this? Any suggestions and comments are highly appreciated!
>
> You didn't mention what Fortran compiler was being used. Probably,
> whichever one it was, it generates debug information that GDB is not
> expecting.

I used g77-3.3.3 on PPC64, and gfortran-4.0.0 on Fedora 4 test 3 on i386.
Both failed (Illegal instruction on PPC64 and SEGV error on i386). I had
some look at the related debuginfo (array "a"), it is indeed an pointer
to array on both platform.

> It sounds like you're right; we should be checking the target type of
> the pointer. Can we end up with a pointer to a string, too?

Sure. But now I am having difficulty in one problem: given an struct value
with the type being TYPE_CODE_PTR, how to get the value of the array (or
string or whatever) it refer to? We need to know this to go on with the
following evaluation. I had thought that function "value_from_pointer"
will do this, but it turn out to be false. Anyone could help on this?

Thanks in advance.

Cheers
- Wu Zhou