[RFC PATCH] Really fix gdb/23010: SYMBOL_LANGUAGE != DICT_LANGUAGE assertion

[Keith Seitz <keiths at redhat dot com>]

This patch is another attempt at really fixing the multitude of assertions
being seen where symbols of one language are being added to symbol lists of
another language.

In short, this is happening because read_file_scope was reading DIEs without
having its language set. As a result, the default language, language_minimal,
was being passed to imported DIE trees and, in certain specific situations,
causing the SYMBOL_LANGUAGE != DICT_LANGUAGE assertion being widely reported.

For a more thorough explanation, see the following mailing list
post:

  https://sourceware.org/ml/gdb-patches/2018-05/msg00703.html

Since a test reproducer for this has been so elusive, this patch also adds a
wrapper function around add_symbol_to_list which asserts  when adding a symbol
of one language to a list containing symbols of a different language.

For this RFC, I have left both the assertion (which I prefer) and the
complaint variation in the patch. I will remove the unused bits upon
approval.

gdb/ChangeLog:

	PR gdb/23010
	* dwarf2read.c (dw2_add_symbol_to_list): New function.
	(fixup_go_packaging, new_symbol): Use dw2_add_symbol_to_list
	instead of add_symbol_to_list.
	(read_file_scope): Call prepare_one_comp_unit before reading
	any other DIEs.
---
 gdb/dwarf2read.c | 38 ++++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 1cabfbb0d4..04f22114f8 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -9701,6 +9701,33 @@ compute_delayed_physnames (struct dwarf2_cu *cu)
   cu->method_list.clear ();
 }
 
+/* A wrapper for add_symbol_to_list to issue a complaint if a symbol
+   with a different language is added to LISTHEAD.  */
+
+static inline void
+dw2_add_symbol_to_list (struct symbol *symbol, struct pending **listhead)
+{
+  /* Only complain if LISTHEAD already contains symbols of a different
+     language.  */
+#if USE_ASSERT
+  gdb_assert ((*listhead) == NULL
+	      || (*listhead)->nsyms == 0
+	      || (SYMBOL_LANGUAGE ((*listhead)->symbol[0])
+		  == SYMBOL_LANGUAGE (symbol)));
+#else
+  if ((*listhead) != NULL && (*listhead)->nsyms > 0
+      && SYMBOL_LANGUAGE ((*listhead)->symbol[0]) != SYMBOL_LANGUAGE (symbol))
+    {
+      complaint (_("recording symbol \"%s\" with language %s "
+		   "into list of langauge %s"), SYMBOL_LINKAGE_NAME (symbol),
+		 language_str (SYMBOL_LANGUAGE (symbol)),
+		 language_str (SYMBOL_LANGUAGE ((*listhead)->symbol[0])));
+    }
+#endif
+
+  add_symbol_to_list (symbol, listhead);
+}
+
 /* Go objects should be embedded in a DW_TAG_module DIE,
    and it's not clear if/how imported objects will appear.
    To keep Go support simple until that's worked out,
@@ -9772,7 +9799,7 @@ fixup_go_packaging (struct dwarf2_cu *cu)
       SYMBOL_ACLASS_INDEX (sym) = LOC_TYPEDEF;
       SYMBOL_TYPE (sym) = type;
 
-      add_symbol_to_list (sym, &global_symbols);
+      dw2_add_symbol_to_list (sym, &global_symbols);
 
       xfree (package_name);
     }
@@ -11438,6 +11465,7 @@ read_file_scope (struct die_info *die, struct dwarf2_cu *cu)
   struct die_info *child_die;
   CORE_ADDR baseaddr;
 
+  prepare_one_comp_unit (cu, die, cu->language);
   baseaddr = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
 
   get_scope_pc_bounds (die, &lowpc, &highpc, cu);
@@ -11450,8 +11478,6 @@ read_file_scope (struct die_info *die, struct dwarf2_cu *cu)
 
   file_and_directory fnd = find_file_and_directory (die, cu);
 
-  prepare_one_comp_unit (cu, die, cu->language);
-
   /* The XLCL doesn't generate DW_LANG_OpenCL because this attribute is not
      standardised yet.  As a workaround for the language detection we fall
      back to the DW_AT_producer string.  */
@@ -21208,7 +21234,7 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
 	  SYMBOL_TYPE (sym) = objfile_type (objfile)->builtin_core_addr;
 	  SYMBOL_DOMAIN (sym) = LABEL_DOMAIN;
 	  SYMBOL_ACLASS_INDEX (sym) = LOC_LABEL;
-	  add_symbol_to_list (sym, cu->list_in_scope);
+	  dw2_add_symbol_to_list (sym, cu->list_in_scope);
 	  break;
 	case DW_TAG_subprogram:
 	  /* SYMBOL_BLOCK_VALUE (sym) will be filled in later by
@@ -21466,7 +21492,7 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
 	case DW_TAG_common_block:
 	  SYMBOL_ACLASS_INDEX (sym) = LOC_COMMON_BLOCK;
 	  SYMBOL_DOMAIN (sym) = COMMON_BLOCK_DOMAIN;
-	  add_symbol_to_list (sym, cu->list_in_scope);
+	  dw2_add_symbol_to_list (sym, cu->list_in_scope);
 	  break;
 	default:
 	  /* Not a tag we recognize.  Hopefully we aren't processing
@@ -21486,7 +21512,7 @@ new_symbol (struct die_info *die, struct type *type, struct dwarf2_cu *cu,
 	}
 
       if (list_to_add != NULL)
-	add_symbol_to_list (sym, list_to_add);
+	dw2_add_symbol_to_list (sym, list_to_add);
 
       /* For the benefit of old versions of GCC, check for anonymous
 	 namespaces based on the demangled name.  */
-- 
2.13.6