Remove null_block_symbol

This removes null_block_symbol.  It seemed simpler to me to change
initializations and returns to use value initialization rather than
null_block_symbol.  This also fixes up a few spots where
initialization was done piecemeal.

gdb/ChangeLog
2019-03-24  Tom Tromey  <tom@tromey.com>

	* ada-lang.c (standard_lookup): Simplify initialization.
	(ada_lookup_symbol_nonlocal): Simplify return.
	* solib-spu.c (spu_lookup_lib_symbol): Simplify return.
	* solib-darwin.c (darwin_lookup_lib_symbol): Simplify return.
	* solib-svr4.c (elf_lookup_lib_symbol): Simplify return.
	* rust-lang.c (rust_lookup_symbol_nonlocal): Simplify
	initialization.
	* solib.c (solib_global_lookup): Simplify.
	* symtab.c (null_block_symbol): Remove.
	(symbol_cache_lookup): Simplify returns.
	(lookup_language_this): Simplify returns.
	(lookup_symbol_aux): Simplify return.
	(lookup_local_symbol): Simplify returns.
	(lookup_global_symbol_from_objfile): Simplify return.
	(lookup_symbol_in_objfile_symtabs)
	(lookup_symbol_in_objfile_from_linkage_name): Simplify return.
	(lookup_symbol_via_quick_fns, lookup_symbol_in_static_block)
	(lookup_static_symbol, lookup_global_symbol): Simplify return.
	* cp-namespace.c (cp_lookup_bare_symbol)
	(cp_search_static_and_baseclasses, cp_lookup_symbol_via_imports)
	(cp_lookup_symbol_via_all_imports, cp_lookup_nested_symbol_1)
	(cp_lookup_nested_symbol): Don't use null_block_symbol.
	(cp_lookup_symbol_via_imports): Simplify initialization.
	(find_symbol_in_baseclass): Likewise.
	* symtab.h (null_block_symbol): Remove.
	* d-namespace.c (d_lookup_symbol): Don't use null_block_symbol.
	(d_lookup_nested_symbol, d_lookup_symbol_imports)
	(d_lookup_symbol_module): Likewise.
	(find_symbol_in_baseclass): Simplify initialization.

Author: tromey

gdb/ChangeLog

@@ -1,3 +1,35 @@
+2019-03-24  Tom Tromey  <tom@tromey.com>
+
+	* ada-lang.c (standard_lookup): Simplify initialization.
+	(ada_lookup_symbol_nonlocal): Simplify return.
+	* solib-spu.c (spu_lookup_lib_symbol): Simplify return.
+	* solib-darwin.c (darwin_lookup_lib_symbol): Simplify return.
+	* solib-svr4.c (elf_lookup_lib_symbol): Simplify return.
+	* rust-lang.c (rust_lookup_symbol_nonlocal): Simplify
+	initialization.
+	* solib.c (solib_global_lookup): Simplify.
+	* symtab.c (null_block_symbol): Remove.
+	(symbol_cache_lookup): Simplify returns.
+	(lookup_language_this): Simplify returns.
+	(lookup_symbol_aux): Simplify return.
+	(lookup_local_symbol): Simplify returns.
+	(lookup_global_symbol_from_objfile): Simplify return.
+	(lookup_symbol_in_objfile_symtabs)
+	(lookup_symbol_in_objfile_from_linkage_name): Simplify return.
+	(lookup_symbol_via_quick_fns, lookup_symbol_in_static_block)
+	(lookup_static_symbol, lookup_global_symbol): Simplify return.
+	* cp-namespace.c (cp_lookup_bare_symbol)
+	(cp_search_static_and_baseclasses, cp_lookup_symbol_via_imports)
+	(cp_lookup_symbol_via_all_imports, cp_lookup_nested_symbol_1)
+	(cp_lookup_nested_symbol): Don't use null_block_symbol.
+	(cp_lookup_symbol_via_imports): Simplify initialization.
+	(find_symbol_in_baseclass): Likewise.
+	* symtab.h (null_block_symbol): Remove.
+	* d-namespace.c (d_lookup_symbol): Don't use null_block_symbol.
+	(d_lookup_nested_symbol, d_lookup_symbol_imports)
+	(d_lookup_symbol_module): Likewise.
+	(find_symbol_in_baseclass): Simplify initialization.
+
 2019-03-24  Tom Tromey  <tom@tromey.com>
 
 	* expression.h: Don't include symtab.h.

gdb/ada-lang.c

@@ -4758,7 +4758,7 @@ standard_lookup (const char *name, const struct block *block,
                  domain_enum domain)
 {
   /* Initialize it just to avoid a GCC false warning.  */
-  struct block_symbol sym = {NULL, NULL};
+  struct block_symbol sym = {};
 
   if (lookup_cached_symbol (name, domain, &sym.symbol, NULL))
     return sym.symbol;
@@ -5918,7 +5918,7 @@ ada_lookup_symbol_nonlocal (const struct language_defn *langdef,
 	return sym;
     }
 
-  return (struct block_symbol) {NULL, NULL};
+  return {};
 }
 
 

gdb/cp-namespace.c

@@ -217,15 +217,15 @@ cp_lookup_bare_symbol (const struct language_defn *langdef,
 	lang_this = lookup_language_this (langdef, block);
 
       if (lang_this.symbol == NULL)
-	return null_block_symbol;
+	return {};
 
 
       type = check_typedef (TYPE_TARGET_TYPE (SYMBOL_TYPE (lang_this.symbol)));
       /* If TYPE_NAME is NULL, abandon trying to find this symbol.
 	 This can happen for lambda functions compiled with clang++,
 	 which outputs no name for the container class.  */
       if (TYPE_NAME (type) == NULL)
-	return null_block_symbol;
+	return {};
 
       /* Look for symbol NAME in this class.  */
       sym = cp_lookup_nested_symbol (type, name, block, domain);
@@ -252,7 +252,7 @@ cp_search_static_and_baseclasses (const char *name,
 {
   /* Check for malformed input.  */
   if (prefix_len + 2 > strlen (name) || name[prefix_len + 1] != ':')
-    return null_block_symbol;
+    return {};
 
   /* The class, namespace or function name is everything up to and
      including PREFIX_LEN.  */
@@ -272,7 +272,7 @@ cp_search_static_and_baseclasses (const char *name,
   if (scope_sym.symbol == NULL)
     scope_sym = lookup_global_symbol (scope.c_str (), block, VAR_DOMAIN);
   if (scope_sym.symbol == NULL)
-    return null_block_symbol;
+    return {};
 
   struct type *scope_type = SYMBOL_TYPE (scope_sym.symbol);
 
@@ -379,13 +379,10 @@ cp_lookup_symbol_via_imports (const char *scope,
 			      const int search_parents)
 {
   struct using_direct *current;
-  struct block_symbol sym;
+  struct block_symbol sym = {};
   int len;
   int directive_match;
 
-  sym.symbol = NULL;
-  sym.block = NULL;
-
   /* First, try to find the symbol in the given namespace if requested.  */
   if (search_scope_first)
     sym = cp_lookup_symbol_in_namespace (scope, name,
@@ -476,7 +473,7 @@ cp_lookup_symbol_via_imports (const char *scope,
 	}
     }
 
-  return null_block_symbol;
+  return {};
 }
 
 /* Helper function that searches an array of symbols for one named NAME.  */
@@ -621,7 +618,7 @@ cp_lookup_symbol_via_all_imports (const char *scope, const char *name,
       block = BLOCK_SUPERBLOCK (block);
     }
 
-  return null_block_symbol;
+  return {};
 }
 
 /* Searches for NAME in the current namespace, and by applying
@@ -808,10 +805,7 @@ find_symbol_in_baseclass (struct type *parent_type, const char *name,
 			  int is_in_anonymous)
 {
   int i;
-  struct block_symbol sym;
-
-  sym.symbol = NULL;
-  sym.block = NULL;
+  struct block_symbol sym = {};
 
   for (i = 0; i < TYPE_N_BASECLASSES (parent_type); ++i)
     {
@@ -902,7 +896,7 @@ cp_lookup_nested_symbol_1 (struct type *container_type,
 	return sym;
     }
 
-  return null_block_symbol;
+  return {};
 }
 
 /* Look up a symbol named NESTED_NAME that is nested inside the C++
@@ -979,7 +973,7 @@ cp_lookup_nested_symbol (struct type *parent_type,
 			      "cp_lookup_nested_symbol (...) = NULL"
 			      " (func/method)\n");
 	}
-      return null_block_symbol;
+      return {};
 
     default:
       internal_error (__FILE__, __LINE__,

gdb/d-namespace.c

@@ -127,7 +127,7 @@ d_lookup_symbol (const struct language_defn *langdef,
 
 	  lang_this = lookup_language_this (language_def (language_d), block);
 	  if (lang_this.symbol == NULL)
-	    return null_block_symbol;
+	    return {};
 
 	  type = check_typedef (TYPE_TARGET_TYPE (SYMBOL_TYPE (lang_this.symbol)));
 	  classname = TYPE_NAME (type);
@@ -147,7 +147,7 @@ d_lookup_symbol (const struct language_defn *langdef,
 	 more that can be done.  */
       class_sym = lookup_global_symbol (classname.c_str (), block, domain);
       if (class_sym.symbol == NULL)
-	return null_block_symbol;
+	return {};
 
       /* Look for a symbol named NESTED in this class.  */
       sym = d_lookup_nested_symbol (SYMBOL_TYPE (class_sym.symbol),
@@ -246,12 +246,9 @@ static struct block_symbol
 find_symbol_in_baseclass (struct type *parent_type, const char *name,
 			  const struct block *block)
 {
-  struct block_symbol sym;
+  struct block_symbol sym = {};
   int i;
 
-  sym.symbol = NULL;
-  sym.block = NULL;
-
   for (i = 0; i < TYPE_N_BASECLASSES (parent_type); ++i)
     {
       struct type *base_type = TYPE_BASECLASS (parent_type, i);
@@ -349,7 +346,7 @@ d_lookup_nested_symbol (struct type *parent_type,
 
     case TYPE_CODE_FUNC:
     case TYPE_CODE_METHOD:
-      return null_block_symbol;
+      return {};
 
     default:
       gdb_assert_not_reached ("called with non-aggregate type.");
@@ -464,7 +461,7 @@ d_lookup_symbol_imports (const char *scope, const char *name,
 	}
     }
 
-  return null_block_symbol;
+  return {};
 }
 
 /* Searches for NAME in the current module, and by applying relevant
@@ -496,7 +493,7 @@ d_lookup_symbol_module (const char *scope, const char *name,
       block = BLOCK_SUPERBLOCK (block);
     }
 
-  return null_block_symbol;
+  return {};
 }
 
 /* The D-specific version of name lookup for static and global names

gdb/rust-lang.c

@@ -2020,7 +2020,7 @@ rust_lookup_symbol_nonlocal (const struct language_defn *langdef,
 			     const struct block *block,
 			     const domain_enum domain)
 {
-  struct block_symbol result = {NULL, NULL};
+  struct block_symbol result = {};
 
   if (symbol_lookup_debug)
     {

gdb/solib-darwin.c

@@ -653,7 +653,7 @@ darwin_lookup_lib_symbol (struct objfile *objfile,
 			  const char *name,
 			  const domain_enum domain)
 {
-  return (struct block_symbol) {NULL, NULL};
+  return {};
 }
 
 static gdb_bfd_ref_ptr

gdb/solib-spu.c

@@ -397,7 +397,7 @@ spu_lookup_lib_symbol (struct objfile *objfile,
 
   if (svr4_so_ops.lookup_lib_global_symbol != NULL)
     return svr4_so_ops.lookup_lib_global_symbol (objfile, name, domain);
-  return (struct block_symbol) {NULL, NULL};
+  return {};
 }
 
 /* Enable shared library breakpoint.  */

gdb/solib-svr4.c

@@ -3204,7 +3204,7 @@ elf_lookup_lib_symbol (struct objfile *objfile,
     }
 
   if (abfd == NULL || scan_dyntag (DT_SYMBOLIC, abfd, NULL, NULL) != 1)
-    return (struct block_symbol) {NULL, NULL};
+    return {};
 
   return lookup_global_symbol_from_objfile (objfile, name, domain);
 }

gdb/solib.c

@@ -1457,7 +1457,7 @@ solib_global_lookup (struct objfile *objfile,
 
   if (ops->lookup_lib_global_symbol != NULL)
     return ops->lookup_lib_global_symbol (objfile, name, domain);
-  return (struct block_symbol) {NULL, NULL};
+  return {};
 }
 
 /* Lookup the value for a specific symbol from dynamic symbol table.  Look