[dwarf] Anonymous nested function causes SEGV during psymbol read

According to the DWARF3 standard, a function always has a name attribute
(Section 3.3 - Subroutine and Entry Point Entries).  The only exception
is when a DW_AT_abstract_origin attribute is provided, in which case
the name may be inherited from the referenced DIE.

The problem occured because our compiler generated a subprogram DIE
for a nested function where the name attribute was missing (and no
abstract-origin either).  Our code in add_partial_symbol is not
prepared to deal with the situation, and happily just tries  to compute
the length of the (NULL) function name.

This normally cannot happen, because there is already a guard in
scan_partial_symbols, where we (silently!) ignore anonymous dies,
including anonymous subprograms. Unfortunately, there is a flaw that
affects Ada and other languages that allow nested subprograms. For
nested subprograms, we do not go through scan_partial_symbols and
thus we are missing the name check.

This patch adds the name check in the nested subprogram case. It also
adds a complaint which is emitted during the psymtab->symtab conversion
phase.

gdb/ChangeLog:

        * dwarf2read.c (add_partial_subprogram): Make sure the subprogram
        DIE has a name before creating the associated partial symbol.
        (read_func_scope): Emit a complaint if the subprogram does not
        have a name or when we can't extract the subprogram PC bounds.

gdb/testsuite/ChangeLog:

        * gdb.dwarf2/dw2-anonymous-func.S: New file.
        * gdb.dwarf2/dw2-anonymous-func.exp: New testcase.

Tested on x86_64-linux, no regression.  Note that the testcase also
verifies that the psymtab->symtab conversion does not crash (this is
the purpose of the "list file1.txt:1" test.

1 files changed, 22 insertions, 5 deletions

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 3789d09..92cda0e6 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -2583,7 +2583,11 @@ add_partial_subprogram (struct partial_die_info *pdi,
 				 cu->per_cu->psymtab);
 	    }
           if (!pdi->is_declaration)
-            add_partial_symbol (pdi, cu);
+	    /* Ignore subprogram DIEs that do not have a name, they are
+	       illegal.  Do not emit a complaint at this point, we will
+	       do so when we convert this psymtab into a symtab.  */
+	    if (pdi->name)
+	      add_partial_symbol (pdi, cu);
         }
     }
   
@@ -3867,10 +3871,23 @@ read_func_scope (struct die_info *die, struct dwarf2_cu *cu)
 
   name = dwarf2_name (die, cu);
 
-  /* Ignore functions with missing or empty names and functions with
-     missing or invalid low and high pc attributes.  */
-  if (name == NULL || !dwarf2_get_pc_bounds (die, &lowpc, &highpc, cu, NULL))
-    return;
+  /* Ignore functions with missing or empty names.  These are actually
+     illegal according to the DWARF standard.  */
+  if (name == NULL)
+    {
+      complaint (&symfile_complaints,
+                 _("missing name for subprogram DIE at %d"), die->offset);
+      return;
+    }
+
+  /* Ignore functions with missing or invalid low and high pc attributes.  */
+  if (!dwarf2_get_pc_bounds (die, &lowpc, &highpc, cu, NULL))
+    {
+      complaint (&symfile_complaints,
+                 _("cannot get low and high bounds for subprogram DIE at %d"),
+                 die->offset);
+      return;
+    }
 
   lowpc += baseaddr;
   highpc += baseaddr;