Mention CU offset for <artifical> if verbose

  Hi,

Say we're debugging a test-case with CUs with name "<artificial>", meaning
not originating from a single file compilation, and use the verbose setting:
...
$ gdb -iex "set verbose on" -batch cc1
Reading symbols from cc1...
Reading in symbols for <artificial>... \
  and /tmp/trunk/gcc/attribs.c... \
  ...
  and /tmp/trunk/gcc/tree-ssa-reassoc.c... \
  done.
...

From the "/tmp/trunk/gcc/attribs.c" message, it's clear which CU is loaded.  But
that's not the case for the "<artificial>" message.

The message uses the filename field of struct partial_symtab, which is
documented like this:
...
  /* Name of the source file which this partial_symtab defines,
     or if the psymtab is anonymous then a descriptive name for
     debugging purposes, or "".  It must not be NULL.  */
...

So, fix this by setting the filename field to a more descriptive name than
"<artificial>", by appending the CU offset.

This way, we print instead:
...
$ gdb -iex "set verbose on" -batch cc1
Reading symbols from cc1...
Reading in symbols for <artificial>@0x41146d9 \
  and /tmp/trunk/gcc/attribs.c... \
  ... \
  and /tmp/trunk/gcc/tree-ssa-reassoc.c... \
  done.
...

Build and reg-tested on x86_64-linux.

OK for trunk?

Thanks,
- Tom

[gdb] Mention CU offset for <artifical> if verbose

gdb/ChangeLog:

2020-02-07  Tom de Vries  <tdevries@suse.de>

	* dwarf2read.c (create_partial_symtab): Append CU offset to filename
	if it matches "<artificial>".

---
 gdb/dwarf2read.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
  

On Fri, Feb 7, 2020 at 6:34 AM Tom de Vries <tdevries@suse.de> wrote:


> diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
> index dafe01d94a..28ade424fd 100644
> --- a/gdb/dwarf2read.c
> +++ b/gdb/dwarf2read.c
> @@ -8020,6 +8020,20 @@ create_partial_symtab (struct dwarf2_per_cu_data *per_cu, const char *name)
>    struct objfile *objfile = per_cu->dwarf2_per_objfile->objfile;
>    dwarf2_psymtab *pst;
>
> +  const char *artificial = "<artificial>";

This may not matter but I'd use static const char artificial[] = "..."

> +  if (strcmp (name, artificial) == 0)
> +    {
> +      sect_offset cu_offset = per_cu->sect_off;
> +      const char *cu_offset_str = sect_offset_str (cu_offset);
> +      const char *sep = "@";
> +      char *new_name = (char *) xmalloc (strlen (artificial) + strlen (sep)
> +                                        + strlen (cu_offset_str) + 1);
> +      strcpy (new_name, artificial);
> +      strcat (new_name, sep);
> +      strcat (new_name, cu_offset_str);

Use concat() instead of malloc/strcpy/strcat?

> +      name = new_name;
> +    }
> +
>    pst = new dwarf2_psymtab (name, objfile, 0);
>
>    pst->psymtabs_addrmap_supported = true;