* buildsym.c (end_symtab): Document that end_symtab can return

NULL under non-error conditions.
 	* dwarfread.c (read_file_scope):  Guard against dereferencing NULL
 	returned from end_symtab for empty compilation units.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+Wed Aug 12 11:14:58 1992  Fred Fish  (fnf@cygnus.com)
+
+	* buildsym.c (end_symtab):  Document that end_symtab can return
+	NULL under non-error conditions.
+	* dwarfread.c (read_file_scope):  Guard against dereferencing NULL
+	returned from end_symtab for empty compilation units.
+
 Tue Aug 11 02:49:39 1992  John Gilmore  (gnu at cygnus.com)
 
 	* am29k-tdep.c:  Lint from DECstation compiler.

gdb/buildsym.c

@@ -549,7 +549,14 @@ start_symtab (name, dirname, start_addr)
    (creating struct block's for them), then make the struct symtab
    for that file and put it in the list of all such.
 
-   END_ADDR is the address of the end of the file's text.  */
+   END_ADDR is the address of the end of the file's text.
+
+   Note that it is possible for end_symtab() to return NULL.  In particular,
+   for the DWARF case at least, it will return NULL when it finds a
+   compilation unit that has exactly one DIE, a TAG_compile_unit DIE.  This
+   can happen when we link in an object file that was compiled from an empty
+   source file.  Returning NULL is probably not the correct thing to do,
+   because then gdb will never know about this empty file (FIXME). */
 
 struct symtab *
 end_symtab (end_addr, sort_pending, sort_linevec, objfile)

gdb/dwarfread.c

@@ -1662,19 +1662,22 @@ read_file_scope (dip, thisdie, enddie, objfile)
   decode_line_numbers (lnbase);
   process_dies (thisdie + dip -> die_length, enddie, objfile);
   symtab = end_symtab (dip -> at_high_pc, 0, 0, objfile);
-  /* FIXME:  The following may need to be expanded for other languages */
-  switch (dip -> at_language)
+  if (symtab != NULL)
     {
-      case LANG_C89:
-      case LANG_C:
-	symtab -> language = language_c;
-	break;
-      case LANG_C_PLUS_PLUS:
-	symtab -> language = language_cplus;
-	break;
-      default:
-	;
-    }
+      /* FIXME:  The following may need to be expanded for other languages */
+      switch (dip -> at_language)
+	{
+	  case LANG_C89:
+	  case LANG_C:
+	    symtab -> language = language_c;
+	    break;
+	  case LANG_C_PLUS_PLUS:
+	    symtab -> language = language_cplus;
+	    break;
+	  default:
+	    ;
+	}
+    }      
   do_cleanups (back_to);
   utypes = NULL;
   numutypes = 0;