diff mbox series

c: Add C2Y N3370 - Case range expressions support [PR117021]

Message ID ZyCzy3EqJmjWclk/@tucnak
State New
Headers
Series c: Add C2Y N3370 - Case range expressions support [PR117021] |

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Commit Message

Jakub Jelinek Oct. 29, 2024, 10:07 a.m. UTC 
  Hi!

The following patch adds the C2Y N3370 paper support.
We had the case ranges as a GNU extension for decades, so this patch
simply:
1) adds different diagnostics when it is used in C (depending on flag_isoc2y
   and pedantic and warn_c23_c2y_compat)
2) emits a pedwarn in C if in a range conversion changes the value of
   the low or high bounds and in that case doesn't emit -Woverflow and
   similar warnings anymore if the pedwarn has been diagnosed
3) changes the handling of empty ranges both in C and C++; previously
   we just warned but let the values be still looked up in the splay
   tree/entered into it (and let only gimplification throw away those
   empty cases), so e.g. case -6 ... -8: break; case -6: break;
   complained about duplicate case label.  But that actually isn't
   duplicate case label, case -6 ... -8: stands for nothing at all
   and that is how it is treated later on (thrown away)

Older version has been bootstrapped/regtested on x86_64-linux and i686-linux
successfully (without the last hunk in c_add_case_label and some of testcase
additions), ok for trunk if even this updated patch passes
bootstrap/regtest?

2024-10-29  Jakub Jelinek  <jakub@redhat.com>

	PR c/117021
gcc/c-family/
	* c-common.cc (c_add_case_label): Emit different diagnostics for C
	on case ranges.  Diagnose for C using pedwarn conversions of range
	expressions changing value and don't emit further conversion
	diagnostics if the pedwarn has been diagnosed.  For empty ranges
	bail out after emitting warning, don't add anything into splay
	trees nor add a CASE_LABEL_EXPR.
gcc/testsuite/
	* gcc.dg/switch-6.c: Expect different diagnostics.  Add -std=gnu23
	to dg-options.
	* gcc.dg/switch-7.c: Expect different diagnostics.  Add -std=c23
	to dg-options.
	* gcc.dg/gnu23-switch-1.c: New test.
	* gcc.dg/gnu23-switch-2.c: New test.
	* gcc.dg/c23-switch-1.c: New test.
	* gcc.dg/c2y-switch-1.c: New test.
	* gcc.dg/c2y-switch-2.c: New test.
	* gcc.dg/c2y-switch-3.c: New test.


	Jakub

Comments

Joseph Myers Oct. 29, 2024, 7:11 p.m. UTC | #1 
On Tue, 29 Oct 2024, Jakub Jelinek wrote:

> Hi!
> 
> The following patch adds the C2Y N3370 paper support.
> We had the case ranges as a GNU extension for decades, so this patch
> simply:
> 1) adds different diagnostics when it is used in C (depending on flag_isoc2y
>    and pedantic and warn_c23_c2y_compat)
> 2) emits a pedwarn in C if in a range conversion changes the value of
>    the low or high bounds and in that case doesn't emit -Woverflow and
>    similar warnings anymore if the pedwarn has been diagnosed
> 3) changes the handling of empty ranges both in C and C++; previously
>    we just warned but let the values be still looked up in the splay
>    tree/entered into it (and let only gimplification throw away those
>    empty cases), so e.g. case -6 ... -8: break; case -6: break;
>    complained about duplicate case label.  But that actually isn't
>    duplicate case label, case -6 ... -8: stands for nothing at all
>    and that is how it is treated later on (thrown away)
> 
> Older version has been bootstrapped/regtested on x86_64-linux and i686-linux
> successfully (without the last hunk in c_add_case_label and some of testcase
> additions), ok for trunk if even this updated patch passes
> bootstrap/regtest?

OK.
diff mbox series

Patch

--- gcc/c-family/c-common.cc.jj	2024-10-29 09:06:12.529014618 +0100
+++ gcc/c-family/c-common.cc	2024-10-29 10:48:36.477959663 +0100
@@ -5186,13 +5186,41 @@  c_add_case_label (location_t loc, splay_
 
   /* Case ranges are a GNU extension.  */
   if (high_value)
-    pedwarn (loc, OPT_Wpedantic,
-	     "range expressions in switch statements are non-standard");
+    {
+      if (c_dialect_cxx ())
+	pedwarn (loc, OPT_Wpedantic,
+		 "range expressions in switch statements are non-standard");
+      else if (warn_c23_c2y_compat > 0)
+	{
+	  if (pedantic && !flag_isoc2y)
+	    pedwarn (loc, OPT_Wc23_c2y_compat,
+		     "ISO C does not support range expressions in switch "
+		     "statements before C2Y");
+	  else
+	    warning_at (loc, OPT_Wc23_c2y_compat,
+			"ISO C does not support range expressions in switch "
+			"statements before C2Y");
+	}
+      else if (warn_c23_c2y_compat && pedantic && !flag_isoc2y)
+	pedwarn (loc, OPT_Wpedantic,
+		 "ISO C does not support range expressions in switch "
+		 "statements before C2Y");
+    }
 
   type = TREE_TYPE (cond);
   if (low_value)
     {
       low_value = check_case_value (loc, low_value);
+      tree tem = NULL_TREE;
+      if (high_value
+	  && !c_dialect_cxx ()
+	  && low_value != error_mark_node
+	  && !int_fits_type_p (low_value, type)
+	  && pedwarn (loc, OPT_Wpedantic,
+		      "conversion of %qE to %qT in range expression changes "
+		      "value to %qE", low_value, type,
+		      (tem = fold_convert (type, low_value))))
+	low_value = tem;
       low_value = convert_and_check (loc, type, low_value);
       low_value = fold (low_value);
       if (low_value == error_mark_node)
@@ -5201,6 +5229,15 @@  c_add_case_label (location_t loc, splay_
   if (high_value)
     {
       high_value = check_case_value (loc, high_value);
+      tree tem = NULL_TREE;
+      if (!c_dialect_cxx ()
+	  && high_value != error_mark_node
+	  && !int_fits_type_p (high_value, type)
+	  && pedwarn (loc, OPT_Wpedantic,
+		      "conversion of %qE to %qT in range expression changes "
+		      "value to %qE", high_value, type,
+		      (tem = fold_convert (type, high_value))))
+	high_value = tem;
       high_value = convert_and_check (loc, type, high_value);
       high_value = fold (high_value);
       if (high_value == error_mark_node)
@@ -5215,7 +5252,10 @@  c_add_case_label (location_t loc, splay_
       if (tree_int_cst_equal (low_value, high_value))
 	high_value = NULL_TREE;
       else if (!tree_int_cst_lt (low_value, high_value))
-	warning_at (loc, 0, "empty range specified");
+	{
+	  warning_at (loc, 0, "empty range specified");
+	  goto error_out;
+	}
     }
 
   /* Look up the LOW_VALUE in the table of case labels we already
--- gcc/testsuite/gcc.dg/switch-6.c.jj	2024-10-29 09:01:53.563641337 +0100
+++ gcc/testsuite/gcc.dg/switch-6.c	2024-10-29 10:08:48.219414989 +0100
@@ -2,13 +2,13 @@ 
    for case ranges with -pedantic.  */
 /* Origin: Joseph Myers <joseph@codesourcery.com> */
 /* { dg-do compile } */
-/* { dg-options "-pedantic" } */
+/* { dg-options "-pedantic -std=gnu23" } */
 
 void
 f (int a)
 {
   switch (a)
     {
-    case 0 ... 0: ; /* { dg-warning "range expressions in switch statements are non-standard" } */
+    case 0 ... 0: ; /* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
     }
 }
--- gcc/testsuite/gcc.dg/switch-7.c.jj	2024-10-29 09:01:53.589640972 +0100
+++ gcc/testsuite/gcc.dg/switch-7.c	2024-10-29 10:08:48.219414989 +0100
@@ -2,13 +2,13 @@ 
    for case ranges with -pedantic-errors.  */
 /* Origin: Joseph Myers <joseph@codesourcery.com> */
 /* { dg-do compile } */
-/* { dg-options "-pedantic-errors" } */
+/* { dg-options "-pedantic-errors -std=c23" } */
 
 void
 f (int a)
 {
   switch (a)
     {
-    case 0 ... 0: ; /* { dg-error "range expressions in switch statements are non-standard" } */
+    case 0 ... 0: ; /* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
     }
 }
--- gcc/testsuite/gcc.dg/gnu23-switch-1.c.jj	2024-10-29 10:08:48.219414989 +0100
+++ gcc/testsuite/gcc.dg/gnu23-switch-1.c	2024-10-29 10:53:34.859778641 +0100
@@ -0,0 +1,100 @@ 
+/* C2Y N3370 - Case range expressions.  */
+/* { dg-do compile } */
+/* { dg-options "-std=gnu23 -pedantic -W -Wall" } */
+
+enum E { F = 10, G = 20 };
+
+void
+foo (unsigned x)
+{
+  switch (x)
+    {
+    case -1:
+      break;
+    case ~0U + 1ULL:			/* { dg-warning "conversion from 'long long unsigned int' to 'unsigned int' changes value from '\[0-9]*' to '0'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+bar (unsigned x)
+{
+  switch (x)
+    {
+    case -2 ... -1:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '-2' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+					/* { dg-warning "conversion of '-1' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-2 } */
+      break;
+    case ~0U + 1ULL ... ~0U + 2ULL:	/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '0'" "" { target *-*-* } .-1 } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '1'" "" { target *-*-* } .-2 } */
+      break;
+    case 70 ... 70:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+      break;
+    case 80 ... 78:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -4 ... -4:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '-4' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+      break;
+    case ~0U + 6ULL ... ~0U + 6ULL:	/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '5'" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+baz (unsigned char x)
+{
+  switch (x)
+    {
+    case -32 ... -30:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "case label value is less than minimum value for type" "" { target *-*-* } .-1 } */
+      break;
+    case -31:				/* { dg-error "duplicate case value" } */
+      break;
+    case -42:				/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -43 ... -41:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "duplicate \\\(or overlapping\\\) case value" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+qux (int x)
+{
+  switch (x)
+    {
+    case -6 ... -8:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -6:
+      break;
+    case -7:
+      break;
+    case -8:
+      break;
+    case F...G:				/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+      break;
+    case -10:
+      break;
+    case -10 ... -11:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -14 ... -15:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -14 ... -15:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
--- gcc/testsuite/gcc.dg/gnu23-switch-2.c.jj	2024-10-29 10:08:48.220414975 +0100
+++ gcc/testsuite/gcc.dg/gnu23-switch-2.c	2024-10-29 10:53:41.986678747 +0100
@@ -0,0 +1,89 @@ 
+/* C2Y N3370 - Case range expressions.  */
+/* { dg-do compile } */
+/* { dg-options "-std=gnu23 -pedantic -W -Wall -Wno-c23-c2y-compat" } */
+
+enum E { F = 10, G = 20 };
+
+void
+foo (unsigned x)
+{
+  switch (x)
+    {
+    case -1:
+      break;
+    case ~0U + 1ULL:			/* { dg-warning "conversion from 'long long unsigned int' to 'unsigned int' changes value from '\[0-9]*' to '0'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+bar (unsigned x)
+{
+  switch (x)
+    {
+    case -2 ... -1:			/* { dg-warning "conversion of '-2' to 'unsigned int' in range expression changes value to '\[0-9]*'" } */
+					/* { dg-warning "conversion of '-1' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+      break;
+    case ~0U + 1ULL ... ~0U + 2ULL:	/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '0'" } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '1'" "" { target *-*-* } .-1 } */
+      break;
+    case 70 ... 70:
+      break;
+    case 80 ... 78:			/* { dg-warning "empty range specified" } */
+      break;
+    case -4 ... -4:			/* { dg-warning "conversion of '-4' to 'unsigned int' in range expression changes value to '\[0-9]*'" } */
+      break;
+    case ~0U + 6ULL ... ~0U + 6ULL:	/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '5'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+baz (unsigned char x)
+{
+  switch (x)
+    {
+    case -32 ... -30:			/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -31:				/* { dg-error "duplicate case value" } */
+      break;
+    case -42:				/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -43 ... -41:			/* { dg-error "duplicate \\\(or overlapping\\\) case value" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+qux (int x)
+{
+  switch (x)
+    {
+    case -6 ... -8:			/* { dg-warning "empty range specified" } */
+      break;
+    case -6:
+      break;
+    case -7:
+      break;
+    case -8:
+      break;
+    case F...G:
+      break;
+    case -10:
+      break;
+    case -10 ... -11:			/* { dg-warning "empty range specified" } */
+      break;
+    case -14 ... -15:			/* { dg-warning "empty range specified" } */
+      break;
+    case -14 ... -15:			/* { dg-warning "empty range specified" } */
+      break;
+    default:
+      break;
+    }
+}
--- gcc/testsuite/gcc.dg/c23-switch-1.c.jj	2024-10-29 10:08:48.220414975 +0100
+++ gcc/testsuite/gcc.dg/c23-switch-1.c	2024-10-29 10:53:22.527951496 +0100
@@ -0,0 +1,100 @@ 
+/* C2Y N3370 - Case range expressions.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23 -pedantic-errors -W -Wall" } */
+
+enum E { F = 10, G = 20 };
+
+void
+foo (unsigned x)
+{
+  switch (x)
+    {
+    case -1:
+      break;
+    case ~0U + 1ULL:			/* { dg-warning "conversion from 'long long unsigned int' to 'unsigned int' changes value from '\[0-9]*' to '0'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+bar (unsigned x)
+{
+  switch (x)
+    {
+    case -2 ... -1:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "conversion of '-2' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+					/* { dg-error "conversion of '-1' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-2 } */
+      break;
+    case ~0U + 1ULL ... ~0U + 2ULL:	/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '0'" "" { target *-*-* } .-1 } */
+					/* { dg-error "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '1'" "" { target *-*-* } .-2 } */
+      break;
+    case 70 ... 70:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+      break;
+    case 80 ... 78:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -4 ... -4:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "conversion of '-4' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+      break;
+    case ~0U + 6ULL ... ~0U + 6ULL:	/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '5'" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+baz (unsigned char x)
+{
+  switch (x)
+    {
+    case -32 ... -30:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "case label value is less than minimum value for type" "" { target *-*-* } .-1 } */
+      break;
+    case -31:				/* { dg-error "duplicate case value" } */
+      break;
+    case -42:				/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -43 ... -41:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "duplicate \\\(or overlapping\\\) case value" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+qux (int x)
+{
+  switch (x)
+    {
+    case -6 ... -8:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -6:
+      break;
+    case -7:
+      break;
+    case -8:
+      break;
+    case F...G:				/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+      break;
+    case -10:
+      break;
+    case -10 ... -11:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -14 ... -15:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -14 ... -15:			/* { dg-error "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
--- gcc/testsuite/gcc.dg/c2y-switch-1.c.jj	2024-10-29 10:08:48.220414975 +0100
+++ gcc/testsuite/gcc.dg/c2y-switch-1.c	2024-10-29 10:52:13.440919866 +0100
@@ -0,0 +1,89 @@ 
+/* C2Y N3370 - Case range expressions.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2y -pedantic -W -Wall" } */
+
+enum E { F = 10, G = 20 };
+
+void
+foo (unsigned x)
+{
+  switch (x)
+    {
+    case -1:
+      break;
+    case ~0U + 1ULL:			/* { dg-warning "conversion from 'long long unsigned int' to 'unsigned int' changes value from '\[0-9]*' to '0'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+bar (unsigned x)
+{
+  switch (x)
+    {
+    case -2 ... -1:			/* { dg-warning "conversion of '-2' to 'unsigned int' in range expression changes value to '\[0-9]*'" } */
+					/* { dg-warning "conversion of '-1' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+      break;
+    case ~0U + 1ULL ... ~0U + 2ULL:	/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '0'" } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '1'" "" { target *-*-* } .-1 } */
+      break;
+    case 70 ... 70:
+      break;
+    case 80 ... 78:			/* { dg-warning "empty range specified" } */
+      break;
+    case -4 ... -4:			/* { dg-warning "conversion of '-4' to 'unsigned int' in range expression changes value to '\[0-9]*'" } */
+      break;
+    case ~0U + 6ULL ... ~0U + 6ULL:	/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '5'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+baz (unsigned char x)
+{
+  switch (x)
+    {
+    case -32 ... -30:			/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -31:				/* { dg-error "duplicate case value" } */
+      break;
+    case -42:				/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -43 ... -41:			/* { dg-error "duplicate \\\(or overlapping\\\) case value" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+qux (int x)
+{
+  switch (x)
+    {
+    case -6 ... -8:			/* { dg-warning "empty range specified" } */
+      break;
+    case -6:
+      break;
+    case -7:
+      break;
+    case -8:
+      break;
+    case F...G:
+      break;
+    case -10:
+      break;
+    case -10 ... -11:			/* { dg-warning "empty range specified" } */
+      break;
+    case -14 ... -15:			/* { dg-warning "empty range specified" } */
+      break;
+    case -14 ... -15:			/* { dg-warning "empty range specified" } */
+      break;
+    default:
+      break;
+    }
+}
--- gcc/testsuite/gcc.dg/c2y-switch-2.c.jj	2024-10-29 10:08:48.220414975 +0100
+++ gcc/testsuite/gcc.dg/c2y-switch-2.c	2024-10-29 10:52:54.576343283 +0100
@@ -0,0 +1,100 @@ 
+/* C2Y N3370 - Case range expressions.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c2y -pedantic -W -Wall -Wc23-c2y-compat" } */
+
+enum E { F = 10, G = 20 };
+
+void
+foo (unsigned x)
+{
+  switch (x)
+    {
+    case -1:
+      break;
+    case ~0U + 1ULL:			/* { dg-warning "conversion from 'long long unsigned int' to 'unsigned int' changes value from '\[0-9]*' to '0'" } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+bar (unsigned x)
+{
+  switch (x)
+    {
+    case -2 ... -1:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '-2' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+					/* { dg-warning "conversion of '-1' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-2 } */
+      break;
+    case ~0U + 1ULL ... ~0U + 2ULL:	/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '0'" "" { target *-*-* } .-1 } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '1'" "" { target *-*-* } .-2 } */
+      break;
+    case 70 ... 70:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+      break;
+    case 80 ... 78:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -4 ... -4:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '-4' to 'unsigned int' in range expression changes value to '\[0-9]*'" "" { target *-*-* } .-1 } */
+      break;
+    case ~0U + 6ULL ... ~0U + 6ULL:	/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "conversion of '\[0-9]*' to 'unsigned int' in range expression changes value to '5'" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+baz (unsigned char x)
+{
+  switch (x)
+    {
+    case -32 ... -30:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "case label value is less than minimum value for type" "" { target *-*-* } .-1 } */
+      break;
+    case -31:				/* { dg-error "duplicate case value" } */
+      break;
+    case -42:				/* { dg-warning "case label value is less than minimum value for type" } */
+      break;
+    case -43 ... -41:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-error "duplicate \\\(or overlapping\\\) case value" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
+
+void
+qux (int x)
+{
+  switch (x)
+    {
+    case -6 ... -8:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -6:
+      break;
+    case -7:
+      break;
+    case -8:
+      break;
+    case F...G:				/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+      break;
+    case -10:
+      break;
+    case -10 ... -11:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -14 ... -15:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    case -14 ... -15:			/* { dg-warning "ISO C does not support range expressions in switch statements before C2Y" } */
+					/* { dg-warning "empty range specified" "" { target *-*-* } .-1 } */
+      break;
+    default:
+      break;
+    }
+}
--- gcc/testsuite/gcc.dg/c2y-switch-3.c.jj	2024-10-29 10:21:51.261442070 +0100
+++ gcc/testsuite/gcc.dg/c2y-switch-3.c	2024-10-29 10:55:27.757196207 +0100
@@ -0,0 +1,40 @@ 
+/* C2Y N3370 - Case range expressions.  */
+/* { dg-do run } */
+/* { dg-options "-std=c2y -pedantic-errors" } */
+
+extern void abort ();
+
+void
+foo (int x)
+{
+  switch (x)
+    {
+    case -42 ... 42:
+      if (x < -42 || x > 42)
+        abort ();
+      break;
+    case 43 ... 43:
+      if (x != 43)
+        abort ();
+      break;
+    case 44:
+      if (x != 44)
+        abort ();
+      break;
+    case 45 ... 46:
+      if (x < 45 || x > 46)
+        abort ();
+      break;
+    default:
+      if (x >= -42 && x <= 46)
+        abort ();
+      break;
+    }
+}
+
+int
+main ()
+{
+  for (int i = -44; i <= 48; ++i)
+    foo (i);
+}