[PATCH][gdb/symtab] Handle invalid partial DIE reference

[Tom de Vries <tdevries@suse.de>]

Hi,

When reverting commit 9cfd2b89bd "[gdb/testsuite] Fix
gdb.arch/amd64-entry-value-paramref.S", we run into an internal-error:
...
(gdb) file amd64-entry-value-paramref^M
Reading symbols from amd64-entry-value-paramref...^M
src/gdb/dwarf2/read.c:18903: internal-error: could not find partial DIE
  0x1b7 in cache [from module amd64-entry-value-paramref]^M

A problem internal to GDB has been detected,^M
further debugging may prove unreliable.^M
...
because of invalid dwarf.

In contrast, when using -readnow, we have:
...
(gdb) file -readnow amd64-entry-value-paramref
Reading symbols from amd64-entry-value-paramref...
Expanding full symbols from amd64-entry-value-paramref...
Dwarf Error: Cannot find DIE at 0x1b7 referenced from DIE at 0x11a \
  [in module amd64-entry-value-paramref]
(gdb)
...

Change the internal error into a Dwarf Error, such that we have:
...
(gdb) file amd64-entry-value-paramref^M
Reading symbols from amd64-entry-value-paramref...^M
Dwarf Error: Cannot not find DIE at 0x1b7 \
  [from module amd64-entry-value-paramref]^M
^M
(No debugging symbols found in amd64-entry-value-paramref)^M
(gdb)
...

Build and tested on x86_64-linux.

Any comments?

Thanks,
- Tom

[gdb/symtab] Handle invalid partial DIE reference

gdb/ChangeLog:

2020-07-24  Tom de Vries  <tdevries@suse.de>

	PR symtab/23270
	* dwarf2/read.c (find_partial_die): Change internal error into Dwarf
	Error.

---
 gdb/dwarf2/read.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 39ed455def..7726f193da 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -18900,9 +18900,7 @@ find_partial_die (sect_offset sect_off, int offset_in_dwz, struct dwarf2_cu *cu)
     }
 
   if (pd == NULL)
-    internal_error (__FILE__, __LINE__,
-		    _("could not find partial DIE %s "
-		      "in cache [from module %s]\n"),
+    error (_("Dwarf Error: Cannot not find DIE at %s [from module %s]\n"),
 		    sect_offset_str (sect_off), bfd_get_filename (objfile->obfd));
   return { cu, pd };
 }