From 8b7a9a249a63e066cff6e95db05a3158b4cc56cc Mon Sep 17 00:00:00 2001
From: Martin Uecker <muecker@gwdg.de>
Date: Sat, 7 Nov 2020 00:48:33 +0100
Subject: [PATCH] C Parser: Implement mixing of labels and code.

Implement mixing of labels and code as adopted for C2X
and process some std-attributes on labels.

2020-11-06  Martin Uecker  <muecker@gwdg.de>

gcc/
	* doc/extend.texi: Document mixing labels and code.
	* doc/invoke.texi: Likewise.

gcc/c/
	* c-parser.c (c_parser_label): Implement mixing of labels and code.
	(c_parser_all_labels): Likewise.

gcc/testsuite/
	* c-c++-common/attr-fallthrough-2.c: Update compiler flags.
	* c-c++-common/Wimplicit-fallthrough-20.c: Adapt test.
	* gcc.dg/20031223-1.c: Update compiler flags and adapt test.
	* gcc.dg/c11-labels-1.c: New test.
	* gcc.dg/c11-labels-2.c: New test.
	* gcc.dg/c11-labels-3.c: New test.
	* gcc.dg/c2x-attr-syntax-3.c: Adapt test.
	* gcc.dg/c2x-labels-1.c: New test.
	* gcc.dg/c2x-labels-2.c: New test.
	* gcc.dg/c2x-labels-3.c: New test.
	* gcc.dg/decl-9.c: Update compiler flags and add error.
	* gcc.dg/gomp/barrier-2.c: Update compiler flags and add warning.
	* gcc.dg/gomp/declare-simd-5.c: Update compiler flags and adapt test.
	* gcc.dg/gomp/declare-variant-2.c: Update compiler flags and add error.
	* gcc.dg/label-compound-stmt-1.c: Update compiler flags.
	* gcc.dg/parse-decl-after-label.c: Update compiler flags.
---
 gcc/c/c-parser.c                              | 105 ++++++------------
 gcc/doc/extend.texi                           |  15 ++-
 gcc/doc/invoke.texi                           |   2 +-
 .../c-c++-common/Wimplicit-fallthrough-20.c   |   6 +-
 .../c-c++-common/attr-fallthrough-2.c         |   2 +-
 gcc/testsuite/gcc.dg/20031223-1.c             |   5 +-
 gcc/testsuite/gcc.dg/c11-labels-1.c           |  15 +++
 gcc/testsuite/gcc.dg/c11-labels-2.c           |  15 +++
 gcc/testsuite/gcc.dg/c11-labels-3.c           |  15 +++
 gcc/testsuite/gcc.dg/c2x-attr-syntax-3.c      |   7 +-
 gcc/testsuite/gcc.dg/c2x-labels-1.c           |  23 ++++
 gcc/testsuite/gcc.dg/c2x-labels-2.c           |  15 +++
 gcc/testsuite/gcc.dg/c2x-labels-3.c           |  38 +++++++
 gcc/testsuite/gcc.dg/decl-9.c                 |   3 +-
 gcc/testsuite/gcc.dg/gomp/barrier-2.c         |   2 +
 gcc/testsuite/gcc.dg/gomp/declare-simd-5.c    |   3 +-
 gcc/testsuite/gcc.dg/gomp/declare-variant-2.c |   3 +-
 gcc/testsuite/gcc.dg/label-compound-stmt-1.c  |   2 +-
 gcc/testsuite/gcc.dg/parse-decl-after-label.c |   2 +-
 19 files changed, 188 insertions(+), 90 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/c11-labels-1.c
 create mode 100644 gcc/testsuite/gcc.dg/c11-labels-2.c
 create mode 100644 gcc/testsuite/gcc.dg/c11-labels-3.c
 create mode 100644 gcc/testsuite/gcc.dg/c2x-labels-1.c
 create mode 100644 gcc/testsuite/gcc.dg/c2x-labels-2.c
 create mode 100644 gcc/testsuite/gcc.dg/c2x-labels-3.c

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index da8278a8257..ecc3d2119fa 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -1521,7 +1521,7 @@ static void c_parser_initval (c_parser *, struct c_expr *,
 			      struct obstack *);
 static tree c_parser_compound_statement (c_parser *, location_t * = NULL);
 static location_t c_parser_compound_statement_nostart (c_parser *);
-static void c_parser_label (c_parser *);
+static void c_parser_label (c_parser *, tree);
 static void c_parser_statement (c_parser *, bool *, location_t * = NULL);
 static void c_parser_statement_after_labels (c_parser *, bool *,
 					     vec<tree> * = NULL);
@@ -5523,7 +5523,7 @@ c_parser_initval (c_parser *parser, struct c_expr *after,
 }
 
 /* Parse a compound statement (possibly a function body) (C90 6.6.2,
-   C99 6.8.2, C11 6.8.2).
+   C99 6.8.2, C11 6.8.2, C2X 6.8.2).
 
    compound-statement:
      { block-item-list[opt] }
@@ -5534,6 +5534,7 @@ c_parser_initval (c_parser *parser, struct c_expr *after,
      block-item-list block-item
 
    block-item:
+     label
      nested-declaration
      statement
 
@@ -5674,7 +5675,7 @@ c_parser_compound_statement_nostart (c_parser *parser)
     {
       location_t loc = c_parser_peek_token (parser)->location;
       loc = expansion_point_location_if_in_system_header (loc);
-      /* Standard attributes may start a statement or a declaration.  */
+      /* Standard attributes may start a label, statement or declaration.  */
       bool have_std_attrs
 	= c_parser_nth_token_starts_std_attributes (parser, 1);
       tree std_attrs = NULL_TREE;
@@ -5685,7 +5686,6 @@ c_parser_compound_statement_nostart (c_parser *parser)
 	  || (c_parser_next_token_is (parser, CPP_NAME)
 	      && c_parser_peek_2nd_token (parser)->type == CPP_COLON))
 	{
-	  c_warn_unused_attributes (std_attrs);
 	  if (c_parser_next_token_is_keyword (parser, RID_CASE))
 	    label_loc = c_parser_peek_2nd_token (parser)->location;
 	  else
@@ -5693,27 +5693,31 @@ c_parser_compound_statement_nostart (c_parser *parser)
 	  last_label = true;
 	  last_stmt = false;
 	  mark_valid_location_for_stdc_pragma (false);
-	  c_parser_label (parser);
+	  c_parser_label (parser, std_attrs);
 	}
-      else if (!last_label
-	       && (c_parser_next_tokens_start_declaration (parser)
-		   || (have_std_attrs
-		       && c_parser_next_token_is (parser, CPP_SEMICOLON))))
+      else if (c_parser_next_tokens_start_declaration (parser)
+	       || (have_std_attrs
+		   && c_parser_next_token_is (parser, CPP_SEMICOLON)))
 	{
-	  last_label = false;
+	  if (last_label)
+	    pedwarn_c11 (c_parser_peek_token (parser)->location, OPT_Wpedantic,
+			 "a label can only be part of a statement and "
+			 "a declaration is not a statement");
+
 	  mark_valid_location_for_stdc_pragma (false);
 	  bool fallthru_attr_p = false;
 	  c_parser_declaration_or_fndef (parser, true, !have_std_attrs,
 					 true, true, true, NULL,
 					 vNULL, have_std_attrs, std_attrs,
 					 NULL, &fallthru_attr_p);
+
 	  if (last_stmt && !fallthru_attr_p)
 	    pedwarn_c90 (loc, OPT_Wdeclaration_after_statement,
 			 "ISO C90 forbids mixed declarations and code");
 	  last_stmt = fallthru_attr_p;
+	  last_label = false;
 	}
-      else if (!last_label
-	       && c_parser_next_token_is_keyword (parser, RID_EXTENSION))
+      else if (c_parser_next_token_is_keyword (parser, RID_EXTENSION))
 	{
 	  /* __extension__ can start a declaration, but is also an
 	     unary operator that can start an expression.  Consume all
@@ -5796,7 +5800,7 @@ c_parser_compound_statement_nostart (c_parser *parser)
       parser->error = false;
     }
   if (last_label)
-    error_at (label_loc, "label at end of compound statement");
+    pedwarn_c11 (label_loc, OPT_Wpedantic, "label at end of compound statement");
   location_t endloc = c_parser_peek_token (parser)->location;
   c_parser_consume_token (parser);
   /* Restore the value we started with.  */
@@ -5812,19 +5816,29 @@ c_parser_compound_statement_nostart (c_parser *parser)
 static void
 c_parser_all_labels (c_parser *parser)
 {
+  tree std_attrs = NULL;
   if (c_parser_nth_token_starts_std_attributes (parser, 1))
     {
-      tree std_attrs = c_parser_std_attribute_specifier_sequence (parser);
+      std_attrs = c_parser_std_attribute_specifier_sequence (parser);
       if (c_parser_next_token_is (parser, CPP_SEMICOLON))
 	c_parser_error (parser, "expected statement");
-      else
-	c_warn_unused_attributes (std_attrs);
     }
   while (c_parser_next_token_is_keyword (parser, RID_CASE)
 	 || c_parser_next_token_is_keyword (parser, RID_DEFAULT)
 	 || (c_parser_next_token_is (parser, CPP_NAME)
 	     && c_parser_peek_2nd_token (parser)->type == CPP_COLON))
-    c_parser_label (parser);
+    {
+      c_parser_label (parser, std_attrs);
+      std_attrs = NULL;
+      if (c_parser_nth_token_starts_std_attributes (parser, 1))
+	{
+	  std_attrs = c_parser_std_attribute_specifier_sequence (parser);
+	  if (c_parser_next_token_is (parser, CPP_SEMICOLON))
+	    c_parser_error (parser, "expected statement");
+	}
+    }
+   if (std_attrs)
+     c_warn_unused_attributes (std_attrs);
 }
 
 /* Parse a label (C90 6.6.1, C99 6.8.1, C11 6.8.1).
@@ -5846,9 +5860,8 @@ c_parser_all_labels (c_parser *parser)
    in the caller, to distinguish statements from declarations.  Any
    attribute-specifier-sequence after the label is parsed in this
    function.  */
-
 static void
-c_parser_label (c_parser *parser)
+c_parser_label (c_parser *parser, tree std_attrs)
 {
   location_t loc1 = c_parser_peek_token (parser)->location;
   tree label = NULL_TREE;
@@ -5898,8 +5911,13 @@ c_parser_label (c_parser *parser)
       if (tlab)
 	{
 	  decl_attributes (&tlab, attrs, 0);
+	  decl_attributes (&tlab, std_attrs, 0);
 	  label = add_stmt (build_stmt (loc1, LABEL_EXPR, tlab));
 	}
+      if (attrs
+	  && c_parser_next_tokens_start_declaration (parser))
+	  warning_at (loc2, OPT_Wattributes, "GNU-style attribute between"
+		      " label and declaration appertains to the label");
     }
   if (label)
     {
@@ -5907,55 +5925,6 @@ c_parser_label (c_parser *parser)
 	FALLTHROUGH_LABEL_P (LABEL_EXPR_LABEL (label)) = fallthrough_p;
       else
 	FALLTHROUGH_LABEL_P (CASE_LABEL (label)) = fallthrough_p;
-
-      /* Standard attributes are only allowed here if they start a
-	 statement, not a declaration (including the case of an
-	 attribute-declaration with only attributes).  */
-      bool have_std_attrs
-	= c_parser_nth_token_starts_std_attributes (parser, 1);
-      tree std_attrs = NULL_TREE;
-      if (have_std_attrs)
-	std_attrs = c_parser_std_attribute_specifier_sequence (parser);
-
-      /* Allow '__attribute__((fallthrough));'.  */
-      if (!have_std_attrs
-	  && c_parser_next_token_is_keyword (parser, RID_ATTRIBUTE))
-	{
-	  location_t loc = c_parser_peek_token (parser)->location;
-	  tree attrs = c_parser_gnu_attributes (parser);
-	  if (attribute_fallthrough_p (attrs))
-	    {
-	      if (c_parser_next_token_is (parser, CPP_SEMICOLON))
-		{
-		  tree fn = build_call_expr_internal_loc (loc,
-							  IFN_FALLTHROUGH,
-							  void_type_node, 0);
-		  add_stmt (fn);
-		}
-	      else
-		warning_at (loc, OPT_Wattributes, "%<fallthrough%> attribute "
-			    "not followed by %<;%>");
-	    }
-	  else if (attrs != NULL_TREE)
-	    warning_at (loc, OPT_Wattributes, "only attribute %<fallthrough%>"
-			" can be applied to a null statement");
-	}
-      if (c_parser_next_tokens_start_declaration (parser)
-	  || (have_std_attrs
-	      && c_parser_next_token_is (parser, CPP_SEMICOLON)))
-	{
-	  error_at (c_parser_peek_token (parser)->location,
-		    "a label can only be part of a statement and "
-		    "a declaration is not a statement");
-	  c_parser_declaration_or_fndef (parser, /*fndef_ok*/ false,
-					 /*static_assert_ok*/ true,
-					 /*empty_ok*/ true, /*nested*/ true,
-					 /*start_attr_ok*/ true, NULL,
-					 vNULL, have_std_attrs, std_attrs);
-	}
-      else if (std_attrs)
-	/* Nonempty attributes on the following statement are ignored.  */
-	c_warn_unused_attributes (std_attrs);
     }
 }
 
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index e6a9bdf1099..5f1e3bf8a2e 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -55,7 +55,7 @@ extensions, accepted by GCC in C90 mode and in C++.
 * Designated Inits::    Labeling elements of initializers.
 * Case Ranges::         `case 1 ... 9' and such.
 * Cast to Union::       Casting to union type from any member of the union.
-* Mixed Declarations::  Mixing declarations and code.
+* Mixed Labels and Declarations::  Mixing declarations, labels and code.
 * Function Attributes:: Declaring that functions have no side effects,
                         or that they can never return.
 * Variable Attributes:: Specifying attributes of variables.
@@ -2353,15 +2353,17 @@ void hack (union foo);
 hack ((union foo) x);
 @end smallexample
 
-@node Mixed Declarations
-@section Mixed Declarations and Code
+@node Mixed Labels and Declarations
+@section Mixed Declarations, Labels and Code
 @cindex mixed declarations and code
 @cindex declarations, mixed with code
 @cindex code, mixed with declarations
 
 ISO C99 and ISO C++ allow declarations and code to be freely mixed
-within compound statements.  As an extension, GNU C also allows this in
-C90 mode.  For example, you could do:
+within compound statements.  ISO C2X allows labels to be
+placed before declarations and at the end of a compound statement.
+As an extension, GNU C also allows all this in C90 mode.  For example,
+you could do:
 
 @smallexample
 int i;
@@ -8630,7 +8632,8 @@ details of the exact syntax for using attributes.  Other attributes are
 available for functions (@pxref{Function Attributes}), variables 
 (@pxref{Variable Attributes}), enumerators (@pxref{Enumerator Attributes}),
 statements (@pxref{Statement Attributes}), and for types
-(@pxref{Type Attributes}).
+(@pxref{Type Attributes}). A label attribute followed
+by a declaration appertains to the label and not the declaration.
 
 This example uses the @code{cold} label attribute to indicate the 
 @code{ErrorHandling} branch is unlikely to be taken and that the
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 271373c381b..d2a188d7c75 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -7630,7 +7630,7 @@ except when the same as the default promotion.
 @opindex Wno-declaration-after-statement
 Warn when a declaration is found after a statement in a block.  This
 construct, known from C++, was introduced with ISO C99 and is by default
-allowed in GCC@.  It is not supported by ISO C90.  @xref{Mixed Declarations}.
+allowed in GCC@.  It is not supported by ISO C90.  @xref{Mixed Labels and Declarations}.
 
 @item -Wshadow
 @opindex Wshadow
diff --git a/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-20.c b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-20.c
index d37a840a0d9..810c331b19a 100644
--- a/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-20.c
+++ b/gcc/testsuite/c-c++-common/Wimplicit-fallthrough-20.c
@@ -27,13 +27,13 @@ g (int i)
   switch (i)
     {
     case -1:
-      __attribute__((used)); /* { dg-warning "ignored|only attribute" } */
+      __attribute__((used)); /* { dg-warning "empty declaration" } */
     default:
-      __attribute__((used)); /* { dg-warning "ignored|only attribute" } */
+      __attribute__((used)); /* { dg-warning "empty declaration" } */
     case 1:
       return 6;
     case 2 ... 4:
-      __attribute__((used)); /* { dg-warning "ignored|only attribute" } */
+      __attribute__((used)); /* { dg-warning "empty declaration" } */
     case 5:
       return 7;
     }
diff --git a/gcc/testsuite/c-c++-common/attr-fallthrough-2.c b/gcc/testsuite/c-c++-common/attr-fallthrough-2.c
index e8659e572ca..be61d5e6666 100644
--- a/gcc/testsuite/c-c++-common/attr-fallthrough-2.c
+++ b/gcc/testsuite/c-c++-common/attr-fallthrough-2.c
@@ -1,6 +1,6 @@
 /* PR c/7652 */
 /* { dg-do compile } */
-/* { dg-options "-Wall -Wextra -Wpedantic -Wno-unused -Wno-implicit-fallthrough" } */
+/* { dg-options "-Wall -Wextra -Wno-unused -Wno-implicit-fallthrough" } */
 
 extern void bar (int);
 void
diff --git a/gcc/testsuite/gcc.dg/20031223-1.c b/gcc/testsuite/gcc.dg/20031223-1.c
index 68aa74ffe50..c529739e7ec 100644
--- a/gcc/testsuite/gcc.dg/20031223-1.c
+++ b/gcc/testsuite/gcc.dg/20031223-1.c
@@ -3,11 +3,10 @@
    because GCC was trying to expand the trees to rtl.  */
 
 /* { dg-do compile } */
-/* { dg-options "" } */
+/* { dg-options "-std=c17 -pedantic-errors" } */
 
 void f ()
 {
  l: int; /* { dg-error "a label can only be part of a statement and a declaration is not a statement" "not stmt" } */
- /* { dg-warning "useless type name in empty declaration" "type name" { target *-*-* } .-1 } */
- /* { dg-error "label at end of compound statement" "label" { target *-*-* } .-2 } */
+ /* { dg-error "useless type name in empty declaration" "type name" { target *-*-* } .-1 } */
 }
diff --git a/gcc/testsuite/gcc.dg/c11-labels-1.c b/gcc/testsuite/gcc.dg/c11-labels-1.c
new file mode 100644
index 00000000000..6350403bf38
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-labels-1.c
@@ -0,0 +1,15 @@
+/* Tests for labels before declarations and at ends of compound statements.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11" } */
+
+int f(int x) 
+{ 
+	goto b;
+	a: int i = 2 * x;
+           goto c;
+	b: goto a;
+	{ i *= 3; c: }
+	return i;
+        d:
+}
+
diff --git a/gcc/testsuite/gcc.dg/c11-labels-2.c b/gcc/testsuite/gcc.dg/c11-labels-2.c
new file mode 100644
index 00000000000..e9b492446b5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-labels-2.c
@@ -0,0 +1,15 @@
+/* Tests for labels before declarations and at ends of compound statements.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic" } */
+
+int f(int x) 
+{ 
+	goto b;
+	a: int i = 2 * x; 	/* { dg-warning "a label can only be part of a statement and a declaration is not a statement" } */
+           goto c;
+	b: goto a;
+	{ i *= 3; c: }		/* { dg-warning "label at end of compound statement" } */
+	return i;
+        d:			/* { dg-warning "label at end of compound statement" } */
+}
+
diff --git a/gcc/testsuite/gcc.dg/c11-labels-3.c b/gcc/testsuite/gcc.dg/c11-labels-3.c
new file mode 100644
index 00000000000..1e4be63af69
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c11-labels-3.c
@@ -0,0 +1,15 @@
+/* Tests for labels before declarations and at ends of compound statements.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+int f(int x) 
+{ 
+	goto b;
+	a: int i = 2 * x;	/* { dg-error "a label can only be part of a statement and a declaration is not a statement" } */
+           goto c;
+	b: goto a;
+	{ i *= 3; c: }		/* { dg-error "label at end of compound statement" } */
+	return i;
+        d:			/* { dg-error "label at end of compound statement" } */
+}
+
diff --git a/gcc/testsuite/gcc.dg/c2x-attr-syntax-3.c b/gcc/testsuite/gcc.dg/c2x-attr-syntax-3.c
index 1f883d825e0..2f0d9f60cc0 100644
--- a/gcc/testsuite/gcc.dg/c2x-attr-syntax-3.c
+++ b/gcc/testsuite/gcc.dg/c2x-attr-syntax-3.c
@@ -25,13 +25,14 @@ f2 (void)
 }
 
 /* Declarations, including attribute declarations, cannot appear after
-   labels.  */
+   labels when a statement is expected.  */
 
 void
 f3 (void)
 {
- x: [[]];; /* { dg-error "can only be part of a statement" } */
-}
+  if (1)
+    x: [[]]; /* { dg-error "expected" } */
+} 
 
 /* Prefix attributes cannot appear on type names.  */
 
diff --git a/gcc/testsuite/gcc.dg/c2x-labels-1.c b/gcc/testsuite/gcc.dg/c2x-labels-1.c
new file mode 100644
index 00000000000..439cf7834ee
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-labels-1.c
@@ -0,0 +1,23 @@
+/* Tests for labels before declarations and at ends of compound statements.  */
+/* { dg-do run } */
+/* { dg-options "-std=c2x -pedantic-errors" } */
+
+int f(int x) 
+{ 
+	goto b;
+	a: int i = 2 * x;
+	aa: int u = 0; int v = 0;
+           goto c;
+	b: goto a;
+	{ i *= 3; c: }
+	return i + u + v;
+        d:
+}
+
+int main(void)
+{
+	if (2 != f(1))
+		__builtin_abort();
+
+	return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/c2x-labels-2.c b/gcc/testsuite/gcc.dg/c2x-labels-2.c
new file mode 100644
index 00000000000..bd010e9ecfb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-labels-2.c
@@ -0,0 +1,15 @@
+/* Tests for labels before declarations and at ends of compound statements.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -Wc11-c2x-compat" } */
+
+int f(int x) 
+{ 
+	goto b;
+	a: int i = 2 * x;	/* { dg-warning "a label can only be part of a statement and a declaration is not a statement" } */
+           goto c;
+	b: goto a;
+	{ i *= 3; c: }		/* { dg-warning "label at end of compound statement" } */
+	return i;
+        d:			/* { dg-warning "label at end of compound statement" } */
+}
+
diff --git a/gcc/testsuite/gcc.dg/c2x-labels-3.c b/gcc/testsuite/gcc.dg/c2x-labels-3.c
new file mode 100644
index 00000000000..159116db186
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c2x-labels-3.c
@@ -0,0 +1,38 @@
+/* Tests for labels before declarations and at ends of compound statements
+ * in combination with attributes. */
+/* { dg-do compile } */
+/* { dg-options "-std=c2x -Wall" } */
+
+int f(void) 
+{ 
+	goto b;
+	a: int i = 0;
+	aa: __attribute__((unused)) int u = 0; int v = 0;	/* { dg-warning "GNU-style attribute between label and declaration appertains to the label" } */
+           goto c;
+	{ c: }
+	b: goto a;
+	return i + u + v;
+        d: __attribute__((unused)) (void)0;
+        e: __attribute__((unused))
+}
+
+int g(void) 
+{ 
+	goto b;
+	a: int i = 0;
+	[[maybe_unused]] aa: int u = 0; int v = 0;
+           goto c;
+	{ c: }
+	b: goto a;
+	return i + u + v;
+        [[maybe_unused]] d: (void)0;
+        [[maybe_unused]] e:
+}
+
+void h(void)
+{
+	[[maybe_unused]] a: [[maybe_unused]] b: [[maybe_unused]] int x;
+
+	if (1)
+		[[maybe_unused]] c: [[maybe_unused]] d: (void)0;
+}
diff --git a/gcc/testsuite/gcc.dg/decl-9.c b/gcc/testsuite/gcc.dg/decl-9.c
index eeca8e05e14..9bb15609d83 100644
--- a/gcc/testsuite/gcc.dg/decl-9.c
+++ b/gcc/testsuite/gcc.dg/decl-9.c
@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-std=gnu89" } */
+/* { dg-options "-std=gnu89 -pedantic-errors" } */
 
 w *x; /* { dg-error "unknown type name 'w'" } */
 
@@ -12,6 +12,7 @@ int f1()
   int d, e;
   d * e; /* { dg-bogus "unknown type name 'd'" } */
   g * h; /* { dg-error "unknown type name 'g'" } */
+  /* { dg-error "mixed declarations" "" { target *-*-* } .-1 } */
   g i;   /* { dg-error "unknown type name 'g'" } */
 }
 
diff --git a/gcc/testsuite/gcc.dg/gomp/barrier-2.c b/gcc/testsuite/gcc.dg/gomp/barrier-2.c
index 5a7091946c4..c0d62f572bb 100644
--- a/gcc/testsuite/gcc.dg/gomp/barrier-2.c
+++ b/gcc/testsuite/gcc.dg/gomp/barrier-2.c
@@ -1,4 +1,5 @@
 /* { dg-do compile } */
+/* { dg-options "-Wall -std=c17 -fopenmp -pedantic-errors" } */
 
 void f1(void)
 {
@@ -16,6 +17,7 @@ void f1(void)
 void f2(void)
 {
   label:       /* { dg-error "label at end of compound statement" } */
+    /* { dg-warning "defined but not used" "" { target *-*-* } .-1 } */
     #pragma omp barrier		/* { dg-error "may only be used in compound statements" } */
 }
 
diff --git a/gcc/testsuite/gcc.dg/gomp/declare-simd-5.c b/gcc/testsuite/gcc.dg/gomp/declare-simd-5.c
index fe236525d62..b9a4161c0c9 100644
--- a/gcc/testsuite/gcc.dg/gomp/declare-simd-5.c
+++ b/gcc/testsuite/gcc.dg/gomp/declare-simd-5.c
@@ -1,5 +1,6 @@
 /* Test parsing of #pragma omp declare simd */
 /* { dg-do compile } */
+/* { dg-options "-std=c17 -fopenmp -pedantic-errors" } */
 
 int
 f1 (int x)
@@ -14,7 +15,7 @@ f1 (int x)
 lab:
     #pragma omp declare simd simdlen (8) aligned (b : 8 * sizeof (int))
     extern int f5 (int a, int *b, int c);	/* { dg-error "must be followed by function declaration or definition" } */
-    x++;					/* { dg-error "expected expression before" "" { target *-*-* } .-1 } */
+    x++;					/* { dg-error "a label can only be part of a statement and a declaration is not a statement" "" { target *-*-* } .-1 } */
   }
   return x;
 }
diff --git a/gcc/testsuite/gcc.dg/gomp/declare-variant-2.c b/gcc/testsuite/gcc.dg/gomp/declare-variant-2.c
index 701d83b0ec3..39c2c1d40ee 100644
--- a/gcc/testsuite/gcc.dg/gomp/declare-variant-2.c
+++ b/gcc/testsuite/gcc.dg/gomp/declare-variant-2.c
@@ -1,5 +1,6 @@
 /* Test parsing of #pragma omp declare variant */
 /* { dg-do compile } */
+/* { dg-options "-std=c17 -fopenmp -pedantic-errors" } */
 
 int f0 (int, int *, int);
 
@@ -16,7 +17,7 @@ f1 (int x)
 lab:
     #pragma omp declare variant (fn0) match (user={condition(0)})
     extern int f5 (int a, int *b, int c);	/* { dg-error "must be followed by function declaration or definition" } */
-    x++;					/* { dg-error "expected expression before" "" { target *-*-* } .-1 } */
+    x++;					/* { dg-error "a label can only be part of a statement and a declaration is not a statement" "" { target *-*-* } .-1 } */
   }
   return x;
 }
diff --git a/gcc/testsuite/gcc.dg/label-compound-stmt-1.c b/gcc/testsuite/gcc.dg/label-compound-stmt-1.c
index 2f8fa4e65c2..2ae2b82ef1c 100644
--- a/gcc/testsuite/gcc.dg/label-compound-stmt-1.c
+++ b/gcc/testsuite/gcc.dg/label-compound-stmt-1.c
@@ -1,7 +1,7 @@
 /* Test that labels at ends of compound statements are hard errors.  */
 /* Origin: Joseph Myers <jsm@polyomino.org.uk> */
 /* { dg-do compile } */
-/* { dg-options "" } */
+/* { dg-options "-std=c17 -pedantic-errors" } */
 
 void f(void) { g: } /* { dg-bogus "warning" "warning in place of error" } */
 /* { dg-error "label|parse|syntax" "label at end of compound statement" { target *-*-* } .-1 } */
diff --git a/gcc/testsuite/gcc.dg/parse-decl-after-label.c b/gcc/testsuite/gcc.dg/parse-decl-after-label.c
index 9c9886a108f..6e2a047eb2e 100644
--- a/gcc/testsuite/gcc.dg/parse-decl-after-label.c
+++ b/gcc/testsuite/gcc.dg/parse-decl-after-label.c
@@ -1,6 +1,6 @@
 /* PR 29062 
 { dg-do compile }
-{ dg-options "-fsyntax-only" }
+{ dg-options "-std=c17 -pedantic-errors -fsyntax-only" }
 */
 
 int f(int x)
-- 
2.30.2