re PR c/70436 (-Wparentheses missing ambiguous else warning)

	PR c/70436
	* c-parser.c (c_parser_statement_after_labels): Add IF_P argument and
	adjust callers.
	(c_parser_statement): Likewise.
	(c_parser_c99_block_statement): Likewise.
	(c_parser_while_statement): Likewise.
	(c_parser_for_statement): Likewise.
	(c_parser_if_body): Don't set IF_P here.
	(c_parser_if_statement): Add IF_P argument.  Set IF_P here.  Warn
	about dangling else here.
	* c-tree.h (c_finish_if_stmt): Adjust declaration.
	* c-typeck.c (c_finish_if_stmt): Remove NESTED_IF parameter.  Don't
	warn about dangling else here.

	* testsuite/gcc.dg/Wparentheses-12.c: New test.
	* testsuite/gcc.dg/Wparentheses-13.c: New test.

From-SVN: r234949

gcc/c/ChangeLog

+2016-04-13  Marek Polacek  <polacek@redhat.com>
+
+	PR c/70436
+	* c-parser.c (c_parser_statement_after_labels): Add IF_P argument and
+	adjust callers.
+	(c_parser_statement): Likewise.
+	(c_parser_c99_block_statement): Likewise.
+	(c_parser_while_statement): Likewise.
+	(c_parser_for_statement): Likewise.
+	(c_parser_if_body): Don't set IF_P here.
+	(c_parser_if_statement): Add IF_P argument.  Set IF_P here.  Warn
+	about dangling else here.
+	* c-tree.h (c_finish_if_stmt): Adjust declaration.
+	* c-typeck.c (c_finish_if_stmt): Remove NESTED_IF parameter.  Don't
+	warn about dangling else here.
+
 2016-04-04  Marek Polacek  <polacek@redhat.com>
 
 	PR c/70307

gcc/c/c-tree.h

@@ -641,7 +641,7 @@ extern tree build_asm_stmt (tree, tree);
 extern int c_types_compatible_p (tree, tree);
 extern tree c_begin_compound_stmt (bool);
 extern tree c_end_compound_stmt (location_t, tree, bool);
-extern void c_finish_if_stmt (location_t, tree, tree, tree, bool);
+extern void c_finish_if_stmt (location_t, tree, tree, tree);
 extern void c_finish_loop (location_t, tree, tree, tree, tree, tree, bool);
 extern tree c_begin_stmt_expr (void);
 extern tree c_finish_stmt_expr (location_t, tree);

gcc/c/c-typeck.c

@@ -9974,12 +9974,11 @@ c_finish_case (tree body, tree type)
 
 /* Emit an if statement.  IF_LOCUS is the location of the 'if'.  COND,
    THEN_BLOCK and ELSE_BLOCK are expressions to be used; ELSE_BLOCK
-   may be null.  NESTED_IF is true if THEN_BLOCK contains another IF
-   statement, and was not surrounded with parenthesis.  */
+   may be null.  */
 
 void
 c_finish_if_stmt (location_t if_locus, tree cond, tree then_block,
-		  tree else_block, bool nested_if)
+		  tree else_block)
 {
   tree stmt;
 
@@ -10011,39 +10010,6 @@ c_finish_if_stmt (location_t if_locus, tree cond, tree then_block,
 	  return;
 	}
     }
-  /* Diagnose an ambiguous else if if-then-else is nested inside if-then.  */
-  if (warn_parentheses && nested_if && else_block == NULL)
-    {
-      tree inner_if = then_block;
-
-      /* We know from the grammar productions that there is an IF nested
-	 within THEN_BLOCK.  Due to labels and c99 conditional declarations,
-	 it might not be exactly THEN_BLOCK, but should be the last
-	 non-container statement within.  */
-      while (1)
-	switch (TREE_CODE (inner_if))
-	  {
-	  case COND_EXPR:
-	    goto found;
-	  case BIND_EXPR:
-	    inner_if = BIND_EXPR_BODY (inner_if);
-	    break;
-	  case STATEMENT_LIST:
-	    inner_if = expr_last (then_block);
-	    break;
-	  case TRY_FINALLY_EXPR:
-	  case TRY_CATCH_EXPR:
-	    inner_if = TREE_OPERAND (inner_if, 0);
-	    break;
-	  default:
-	    gcc_unreachable ();
-	  }
-    found:
-
-      if (COND_EXPR_ELSE (inner_if))
-	 warning_at (if_locus, OPT_Wparentheses,
-		     "suggest explicit braces to avoid ambiguous %<else%>");
-    }
 
   stmt = build3 (COND_EXPR, void_type_node, cond, then_block, else_block);
   SET_EXPR_LOCATION (stmt, if_locus);

gcc/testsuite/ChangeLog

+2016-04-13  Marek Polacek  <polacek@redhat.com>
+
+	PR c/70436
+	* testsuite/gcc.dg/Wparentheses-12.c: New test.
+	* testsuite/gcc.dg/Wparentheses-13.c: New test.
+
 2016-04-13  Ilya Enkovich  <ilya.enkovich@intel.com>
 
 	* gcc.target/i386/avx512bw-kunpckdq-2.c: New test.

gcc/testsuite/gcc.dg/Wparentheses-12.c

+/* PR c/70436  */
+/* { dg-options "-Wparentheses" }  */
+
+int a, b, c;
+void bar (void);
+void baz (void);
+
+void
+foo (void)
+{
+  int i, j;
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    for (;;)
+      if (b)
+        bar ();
+      else
+        baz ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    while (1)
+      if (b)
+        bar ();
+      else
+        baz ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    while (1)
+      for (;;)
+        if (b)
+          bar ();
+        else
+          baz ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    while (1)
+      while (1)
+        if (b)
+          bar ();
+  else
+    baz ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    for (i = 0; i < 10; i++)
+      for (j = 0; j < 10; j++)
+        if (b)
+          bar ();
+  else
+    baz ();
+
+  if (a)
+    for (i = 0; i < 10; i++)
+      if (b) /* { dg-warning "ambiguous" }  */
+        for (j = 0; j < 10; j++)
+          if (c)
+            bar ();
+      else
+        baz ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    for (i = 0; i < 10; i++)
+      if (b)
+        for (j = 0; j < 10; j++)
+          if (c)
+            bar ();
+          else
+            baz ();
+  else
+    bar ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    for (;;)
+      if (b)
+        while (1)
+          if (a)
+            bar ();
+          else
+            baz ();
+      else
+        bar ();
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    for (;;)
+      if (b)
+        while (1)
+          {
+            if (a) { bar (); } else { baz (); }
+          }
+      else
+        bar ();
+
+  if (a)
+    for (;;)
+      if (b)
+        bar ();
+      else
+        baz ();
+  else bar ();
+
+  if (a)
+    while (1)
+      if (b)
+        bar ();
+      else
+        baz ();
+  else bar ();
+
+  if (a)
+    for (;;)
+      {
+        if (b)
+          bar ();
+        else
+          baz ();
+      }
+
+  if (a)
+    {
+      for (;;)
+        if (b)
+          bar ();
+    }
+  else baz ();
+
+  if (a)
+    do
+      if (b) bar (); else baz ();
+    while (b);
+
+  if (a)
+    do
+      if (b) bar ();
+    while (b);
+  else baz ();
+}

gcc/testsuite/gcc.dg/Wparentheses-13.c

+/* PR c/70436  */
+/* { dg-options "-Wparentheses" }  */
+
+int a, b, c;
+void bar (int);
+
+void
+foo (void)
+{
+  if (a) /* { dg-warning "ambiguous" }  */
+    if (b)
+      {
+	if (c)
+	  bar (0);
+      }
+    else
+      bar (1);
+
+  if (a > 0)
+    if (a > 1)
+      if (a > 2)
+	if (a > 3)
+	  if (a > 4)
+	    if (a > 5) /* { dg-warning "ambiguous" }  */
+	      if (a > 6)
+		while (1)
+		  bar (0);
+  else
+    bar (1);
+
+  if (a) /* { dg-warning "ambiguous" }  */
+    if (b)
+      switch (c);
+    else
+      bar (1);
+
+  switch (a)
+  {
+  default:
+    if (b) /* { dg-warning "ambiguous" }  */
+      if (c)
+	for (;;)
+          bar (0);
+    else
+      bar (1);
+  }
+
+  if (a) /* { dg-warning "ambiguous" }  */
+  if (a)
+    {
+      bar (2);
+    }
+  else
+    bar (3);
+
+  if (a)
+    do if (b) bar (4); while (1);
+  else bar (5);
+
+  do
+    {
+      if (a)
+        if (b) /* { dg-warning "ambiguous" }  */
+         if (c) for (;;) bar (6);
+     else bar (7);
+    } while (0);
+}