re PR c++/5520 (Add a warning to detect empty body of if statements (like in the C frontend))

2006-01-20  Dirk Mueller  <dmueller@suse.com>

        PR c++/5520
        * c-parser.c (c_parser_if_body): Use build_empty_stmt()
        instead of a special NOP marker.
        * c-typeck.c (c_finish_if_stmt): Remove obsoleted special
        NOP marker handling.
        * c-common.h (empty_body_warning): Add forward declaration.
        * c-common.c (empty_body_warning): Add (from c_finish_if_stmt).
        Now uses IS_EMPTY_STMT() instead of special NOP markers.

        * semantics.c (finish_if_stmt): Call empty_body_warning.
        * parser.c (cp_parser_implicitly_scoped_statement):
        Mark empty statement with an empty stmt.

        * g++.dg/warn/empty-body.C: New.

From-SVN: r110019

10 files changed, 79 insertions, 35 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4e21b29..0a23c22 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,14 @@
+2006-01-20  Dirk Mueller  <dmueller@suse.com>
+
+        PR c++/5520
+        * c-parser.c (c_parser_if_body): Use build_empty_stmt()
+        instead of a special NOP marker.
+        * c-typeck.c (c_finish_if_stmt): Remove obsoleted special
+        NOP marker handling.
+        * c-common.h (empty_body_warning): Add forward declaration.
+        * c-common.c (empty_body_warning): Add (from c_finish_if_stmt).
+        Now uses IS_EMPTY_STMT() instead of special NOP markers.
+
 2005-01-20  Paul Brook  <paul@codesourcery.com>
 
 	* Makefile.in (lang_checks): Keep going if mkdir fails.
diff --git a/gcc/c-common.c b/gcc/c-common.c
index 2a7c1e7..60035ea 100644
--- a/gcc/c-common.c
+++ b/gcc/c-common.c
@@ -994,6 +994,36 @@ strict_aliasing_warning(tree otype, tree type, tree expr)
     }
 }
 
+
+/* Print a warning about if (); or if () .. else; constructs
+   via the special empty statement node that we create.  INNER_THEN
+   and INNER_ELSE are the statement lists of the if and the else
+   block.  */
+
+void
+empty_body_warning (tree inner_then, tree inner_else)
+{
+  if (extra_warnings)
+    {
+      if (TREE_CODE (inner_then) == STATEMENT_LIST
+	  && STATEMENT_LIST_TAIL (inner_then))
+	inner_then = STATEMENT_LIST_TAIL (inner_then)->stmt;
+
+      if (inner_else && TREE_CODE (inner_else) == STATEMENT_LIST
+	  && STATEMENT_LIST_TAIL (inner_else))
+	inner_else = STATEMENT_LIST_TAIL (inner_else)->stmt;
+
+      if (IS_EMPTY_STMT (inner_then) && !inner_else)
+	warning (OPT_Wextra, "%Hempty body in an if-statement",
+		 EXPR_LOCUS (inner_then));
+
+      if (inner_else && IS_EMPTY_STMT (inner_else))
+	warning (OPT_Wextra, "%Hempty body in an else-statement",
+		 EXPR_LOCUS (inner_else));
+   }
+}
+
+  
 /* Nonzero if constant C has a value that is permissible
    for type TYPE (an INTEGER_TYPE).  */
 
diff --git a/gcc/c-common.h b/gcc/c-common.h
index 6da433c..ba7dc5c 100644
--- a/gcc/c-common.h
+++ b/gcc/c-common.h
@@ -655,6 +655,7 @@ extern tree fix_string_type (tree);
 struct varray_head_tag;
 extern void constant_expression_warning (tree);
 extern void strict_aliasing_warning(tree, tree, tree);
+extern void empty_body_warning (tree, tree);
 extern tree convert_and_check (tree, tree);
 extern void overflow_warning (tree);
 extern void unsigned_conversion_warning (tree, tree);
diff --git a/gcc/c-parser.c b/gcc/c-parser.c
index e594d1f..a5fa523 100644
--- a/gcc/c-parser.c
+++ b/gcc/c-parser.c
@@ -3804,7 +3804,7 @@ c_parser_if_body (c_parser *parser, bool *if_p)
     c_parser_label (parser);
   *if_p = c_parser_next_token_is_keyword (parser, RID_IF);
   if (extra_warnings && c_parser_next_token_is (parser, CPP_SEMICOLON))
-    add_stmt (build1 (NOP_EXPR, NULL_TREE, NULL_TREE));
+    add_stmt (build_empty_stmt ());
   c_parser_statement_after_labels (parser);
   return c_end_compound_stmt (block, flag_isoc99);
 }
diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index 06ffefd..c6f658b 100644
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -7186,36 +7186,7 @@ c_finish_if_stmt (location_t if_locus, tree cond, tree then_block,
 		  &if_locus);
     }
 
-  /* Diagnose ";" via the special empty statement node that we create.  */
-  if (extra_warnings)
-    {
-      tree *inner_then = &then_block, *inner_else = &else_block;
-
-      if (TREE_CODE (*inner_then) == STATEMENT_LIST
-	  && STATEMENT_LIST_TAIL (*inner_then))
-	inner_then = &STATEMENT_LIST_TAIL (*inner_then)->stmt;
-      if (*inner_else && TREE_CODE (*inner_else) == STATEMENT_LIST
-	  && STATEMENT_LIST_TAIL (*inner_else))
-	inner_else = &STATEMENT_LIST_TAIL (*inner_else)->stmt;
-
-      if (TREE_CODE (*inner_then) == NOP_EXPR && !TREE_TYPE (*inner_then))
-	{
-	  if (!*inner_else)
-	    warning (0, "%Hempty body in an if-statement",
-		     EXPR_LOCUS (*inner_then));
-
-	  *inner_then = alloc_stmt_list ();
-	}
-      if (*inner_else
-	  && TREE_CODE (*inner_else) == NOP_EXPR
-	  && !TREE_TYPE (*inner_else))
-	{
-	  warning (0, "%Hempty body in an else-statement",
-		   EXPR_LOCUS (*inner_else));
-
-	  *inner_else = alloc_stmt_list ();
-	}
-    }
+  empty_body_warning (then_block, else_block);
 
   stmt = build3 (COND_EXPR, void_type_node, cond, then_block, else_block);
   SET_EXPR_LOCATION (stmt, if_locus);
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 5fabf49..b54d930 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2006-01-20  Dirk Mueller  <dmueller@suse.com>
+
+        PR c++/5520
+        * semantics.c (finish_if_stmt): Call empty_body_warning.
+        * parser.c (cp_parser_implicitly_scoped_statement):
+        Mark empty statement with an empty stmt.
+
 2006-01-19  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/22136
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index d2b41e5..cf19fbf 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -6827,8 +6827,17 @@ cp_parser_implicitly_scoped_statement (cp_parser* parser)
 {
   tree statement;
 
+  /* Mark if () ; with a special NOP_EXPR.  */
+  if (cp_lexer_next_token_is (parser->lexer, CPP_SEMICOLON))
+    {
+      cp_lexer_consume_token (parser->lexer);
+      statement = add_stmt (build_empty_stmt ());
+    }
+  /* if a compound is opened, we simply parse the statement directly.  */
+  else if (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE))
+    statement = cp_parser_compound_statement (parser, NULL, false);
   /* If the token is not a `{', then we must take special action.  */
-  if (cp_lexer_next_token_is_not (parser->lexer, CPP_OPEN_BRACE))
+  else
     {
       /* Create a compound-statement.  */
       statement = begin_compound_stmt (0);
@@ -6837,9 +6846,6 @@ cp_parser_implicitly_scoped_statement (cp_parser* parser)
       /* Finish the dummy compound-statement.  */
       finish_compound_stmt (statement);
     }
-  /* Otherwise, we simply parse the statement directly.  */
-  else
-    statement = cp_parser_compound_statement (parser, NULL, false);
 
   /* Return the statement.  */
   return statement;
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 512b789..6121d43 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -670,6 +670,7 @@ finish_if_stmt (tree if_stmt)
   TREE_CHAIN (if_stmt) = NULL;
   add_stmt (do_poplevel (scope));
   finish_stmt ();
+  empty_body_warning (THEN_CLAUSE (if_stmt), ELSE_CLAUSE (if_stmt));
 }
 
 /* Begin a while-statement.  Returns a newly created WHILE_STMT if
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b41928e..c0cc342 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-01-20  Dirk Mueller  <dmueller@suse.com>
+
+        PR c++/5520
+        * g++.dg/warn/empty-body.C: New.
+
 2006-01-19  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/22136
diff --git a/gcc/testsuite/g++.dg/warn/empty-body.C b/gcc/testsuite/g++.dg/warn/empty-body.C
new file mode 100644
index 0000000..6ca8900
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/empty-body.C
@@ -0,0 +1,12 @@
+// PR c++/5520
+// { dg-options "-O2 -Wextra" }
+
+void breakme()
+{
+  if(1) ;   // { dg-warning "empty body" }
+  if(1) {}  // { dg-bogus "empty body" }
+  if(1) (void)0; // { dg-bogus "empty body" }
+  if(1) {} else; // { dg-warning "empty body" }
+  if(1) {} else (void)0; // // { dg-bogus "empty body" }
+  if(1) ;  else (void)0; // // { dg-bogus "empty body" }
+}