diff mbox series

c++: P2865R5, Remove Deprecated Array Comparisons from C++26 [PR117788]

Message ID 20241128020605.1401357-1-polacek@redhat.com
State New
Headers
Series c++: P2865R5, Remove Deprecated Array Comparisons from C++26 [PR117788] |

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Commit Message

Marek Polacek Nov. 28, 2024, 2:06 a.m. UTC 
  Not a bugfix, but this should only affect C++26.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8-- 
This patch implements P2865R5 by promoting the warning to error in C++26
only.  -Wno-array-compare shouldn't disable the error, so adjust the call
sites as well.

In C++20 we should warn even without -Wall.  Jason fixed this in r15-5713
but let's add a test that doesn't use -Wall.

	PR c++/117788

gcc/c-family/ChangeLog:

	* c-warn.cc (do_warn_array_compare): Emit an error in C++26.

gcc/cp/ChangeLog:

	* typeck.cc (cp_build_binary_op) <case EQ_EXPR>: Don't check
	warn_array_compare.  Check tf_warning_or_error instead of just
	tf_warning.
	<case LE_EXPR>: Likewise.

gcc/testsuite/ChangeLog:

	* c-c++-common/Warray-compare-1.c: Expect an error in C++26.
	* c-c++-common/Warray-compare-2.c: Likewise.
	* c-c++-common/Warray-compare-3.c: Likewise.
	* c-c++-common/Warray-compare-4.c: New test.
	* g++.dg/tree-ssa/pr15791-1.C: Expect an error in C++26.
---
 gcc/c-family/c-warn.cc                        | 25 +++++++---
 gcc/cp/typeck.cc                              | 10 ++--
 gcc/testsuite/c-c++-common/Warray-compare-1.c | 21 +++++---
 gcc/testsuite/c-c++-common/Warray-compare-2.c | 21 +++++---
 gcc/testsuite/c-c++-common/Warray-compare-3.c |  7 +--
 gcc/testsuite/c-c++-common/Warray-compare-4.c | 50 +++++++++++++++++++
 gcc/testsuite/g++.dg/tree-ssa/pr15791-1.C     |  2 +-
 7 files changed, 106 insertions(+), 30 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/Warray-compare-4.c


base-commit: 1046c32de4956c3d706a2ff8683582fd21b8f360

Comments

Jason Merrill Nov. 28, 2024, 5:04 p.m. UTC | #1 
On 11/27/24 9:06 PM, Marek Polacek wrote:
> Not a bugfix, but this should only affect C++26.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> -- >8--
> This patch implements P2865R5 by promoting the warning to error in C++26
> only.  -Wno-array-compare shouldn't disable the error, so adjust the call
> sites as well.

I think it's fine for -Wno-array-compare to suppress the error (and
-Wno-error=array-compare to reduce it to a warning), so how about 
DK_PERMERROR rather than DK_ERROR?

We also need SFINAE for this when !tf_warning_or_error.

Jason
diff mbox series

Patch

diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index 05d6e37edae..acda9a3ee3d 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -3818,8 +3818,9 @@  maybe_warn_sizeof_array_div (location_t loc, tree arr, tree arr_type,
 
 /* Warn about C++20 [depr.array.comp] array comparisons: "Equality
    and relational comparisons between two operands of array type are
-   deprecated."  We also warn in C and earlier C++ standards.  CODE is
-   the code for this comparison, OP0 and OP1 are the operands.  */
+   deprecated."  In C++26 this is an error.  We also warn in C and earlier
+   C++ standards.  CODE is the code for this comparison, OP0 and OP1 are
+   the operands.  */
 
 void
 do_warn_array_compare (location_t location, tree_code code, tree op0, tree op1)
@@ -3832,10 +3833,22 @@  do_warn_array_compare (location_t location, tree_code code, tree op0, tree op1)
     op1 = TREE_OPERAND (op1, 0);
 
   auto_diagnostic_group d;
-  if (warning_at (location, OPT_Warray_compare,
-		  (c_dialect_cxx () && cxx_dialect >= cxx20)
-		  ? G_("comparison between two arrays is deprecated in C++20")
-		  : G_("comparison between two arrays")))
+  diagnostic_t kind = DK_WARNING;
+  const char *msg;
+  if (c_dialect_cxx () && cxx_dialect >= cxx20)
+    {
+      /* P2865R5 made this comparison ill-formed in C++26.  */
+      if (cxx_dialect >= cxx26)
+	{
+	  msg = G_("comparison between two arrays is not allowed in C++26");
+	  kind = DK_ERROR;
+	}
+      else
+	msg = G_("comparison between two arrays is deprecated in C++20");
+    }
+  else
+    msg = G_("comparison between two arrays");
+  if (emit_diagnostic (kind, location, OPT_Warray_compare, msg))
     {
       /* C doesn't allow +arr.  */
       if (c_dialect_cxx ())
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 102a8ed131c..c3895eb5fb2 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -5816,7 +5816,7 @@  cp_build_binary_op (const op_location_t &location,
 	warning_at (location, OPT_Wfloat_equal,
 		    "comparing floating-point with %<==%> "
 		    "or %<!=%> is unsafe");
-      if (complain & tf_warning)
+      if (complain & tf_warning_or_error)
 	{
 	  tree stripped_orig_op0 = tree_strip_any_location_wrapper (orig_op0);
 	  tree stripped_orig_op1 = tree_strip_any_location_wrapper (orig_op1);
@@ -5827,8 +5827,7 @@  cp_build_binary_op (const op_location_t &location,
 	    warning_at (location, OPT_Waddress,
 			"comparison with string literal results in "
 			"unspecified behavior");
-	  else if (warn_array_compare
-		   && TREE_CODE (TREE_TYPE (orig_op0)) == ARRAY_TYPE
+	  else if (TREE_CODE (TREE_TYPE (orig_op0)) == ARRAY_TYPE
 		   && TREE_CODE (TREE_TYPE (orig_op1)) == ARRAY_TYPE)
 	    do_warn_array_compare (location, code, stripped_orig_op0,
 				   stripped_orig_op1);
@@ -6111,11 +6110,10 @@  cp_build_binary_op (const op_location_t &location,
 			"comparison with string literal results "
 			"in unspecified behavior");
 	}
-      else if (warn_array_compare
-	       && TREE_CODE (TREE_TYPE (orig_op0)) == ARRAY_TYPE
+      else if (TREE_CODE (TREE_TYPE (orig_op0)) == ARRAY_TYPE
 	       && TREE_CODE (TREE_TYPE (orig_op1)) == ARRAY_TYPE
 	       && code != SPACESHIP_EXPR
-	       && (complain & tf_warning))
+	       && (complain & tf_warning_or_error))
 	do_warn_array_compare (location, code,
 			       tree_strip_any_location_wrapper (orig_op0),
 			       tree_strip_any_location_wrapper (orig_op1));
diff --git a/gcc/testsuite/c-c++-common/Warray-compare-1.c b/gcc/testsuite/c-c++-common/Warray-compare-1.c
index 922396c0a1a..90191ecd056 100644
--- a/gcc/testsuite/c-c++-common/Warray-compare-1.c
+++ b/gcc/testsuite/c-c++-common/Warray-compare-1.c
@@ -14,12 +14,18 @@  int arr4[2][2];
 bool
 g ()
 {
-  bool b = arr1 == arr2; /* { dg-warning "comparison between two arrays" } */
-  b &= arr1 != arr2; /* { dg-warning "comparison between two arrays" } */
-  b &= arr1 > arr2; /* { dg-warning "comparison between two arrays" } */
-  b &= arr1 >= arr2; /* { dg-warning "comparison between two arrays" } */
-  b &= arr1 < arr2; /* { dg-warning "comparison between two arrays" } */
-  b &= arr1 <= arr2; /* { dg-warning "comparison between two arrays" } */
+  bool b = arr1 == arr2; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 != arr2; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 > arr2; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 >= arr2; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 < arr2; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 <= arr2; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
 #ifdef __cplusplus
   b &= +arr1 == +arr2;
   b &= +arr1 != +arr2;
@@ -35,7 +41,8 @@  g ()
   b &= &arr1[0] < &arr2[0];
   b &= &arr1[0] <= &arr2[0];
 
-  b &= arr3 == arr4; /* { dg-warning "comparison between two arrays" } */
+  b &= arr3 == arr4; /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
 
 #if defined(__cplusplus) && __cplusplus > 201703L
   auto cmp = arr1 <=> arr2; /* { dg-error "invalid operands" "" { target c++20 } } */
diff --git a/gcc/testsuite/c-c++-common/Warray-compare-2.c b/gcc/testsuite/c-c++-common/Warray-compare-2.c
index b3688e69b37..c5af1409eb7 100644
--- a/gcc/testsuite/c-c++-common/Warray-compare-2.c
+++ b/gcc/testsuite/c-c++-common/Warray-compare-2.c
@@ -14,12 +14,18 @@  int arr4[2][2];
 bool
 g ()
 {
-  bool b = arr1 == arr2; /* { dg-bogus "comparison between two arrays" } */
-  b &= arr1 != arr2; /* { dg-bogus "comparison between two arrays" } */
-  b &= arr1 > arr2; /* { dg-bogus "comparison between two arrays" } */
-  b &= arr1 >= arr2; /* { dg-bogus "comparison between two arrays" } */
-  b &= arr1 < arr2; /* { dg-bogus "comparison between two arrays" } */
-  b &= arr1 <= arr2; /* { dg-bogus "comparison between two arrays" } */
+  bool b = arr1 == arr2; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 != arr2; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 > arr2; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 >= arr2; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 < arr2; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 <= arr2; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
 #ifdef __cplusplus
   b &= +arr1 == +arr2;
   b &= +arr1 != +arr2;
@@ -35,7 +41,8 @@  g ()
   b &= &arr1[0] < &arr2[0];
   b &= &arr1[0] <= &arr2[0];
 
-  b &= arr3 == arr4; /* { dg-bogus "comparison between two arrays" } */
+  b &= arr3 == arr4; /* { dg-bogus "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
 
 #if defined(__cplusplus) && __cplusplus > 201703L
   auto cmp = arr1 <=> arr2; /* { dg-error "invalid operands" "" { target c++20 } } */
diff --git a/gcc/testsuite/c-c++-common/Warray-compare-3.c b/gcc/testsuite/c-c++-common/Warray-compare-3.c
index 4725aa2b38b..afcc934010e 100644
--- a/gcc/testsuite/c-c++-common/Warray-compare-3.c
+++ b/gcc/testsuite/c-c++-common/Warray-compare-3.c
@@ -7,7 +7,8 @@  int a[32][32], b[32][32];
 int
 foo (int x, int y)
 {
-  return (x ? a : b) == (y ? a : b); /* { dg-warning "comparison between two arrays" } */
-/* { dg-message "use '&\\\(\[^\n\r]*\\\)\\\[0\\\] == &\\\(\[^\n\r]*\\\)\\\[0\\\]' to compare the addresses" "" { target c } .-1 } */
-/* { dg-message "use unary '\\\+' which decays operands to pointers or '&\\\(\[^\n\r]*\\\)\\\[0\\\] == &\\\(\[^\n\r]*\\\)\\\[0\\\]' to compare the addresses" "" { target c++ } .-2 } */
+  return (x ? a : b) == (y ? a : b); /* { dg-warning "comparison between two arrays" "" { target { c || c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+/* { dg-message "use '&\\\(\[^\n\r]*\\\)\\\[0\\\] == &\\\(\[^\n\r]*\\\)\\\[0\\\]' to compare the addresses" "" { target c } .-2 } */
+/* { dg-message "use unary '\\\+' which decays operands to pointers or '&\\\(\[^\n\r]*\\\)\\\[0\\\] == &\\\(\[^\n\r]*\\\)\\\[0\\\]' to compare the addresses" "" { target c++ } .-3 } */
 }
diff --git a/gcc/testsuite/c-c++-common/Warray-compare-4.c b/gcc/testsuite/c-c++-common/Warray-compare-4.c
new file mode 100644
index 00000000000..8cfb4b2ffe6
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/Warray-compare-4.c
@@ -0,0 +1,50 @@ 
+/* PR c++/97573 */
+/* { dg-do compile } */
+
+#ifndef __cplusplus
+# define bool _Bool
+#endif
+
+int arr1[5];
+int arr2[5];
+int arr3[2][2];
+int arr4[2][2];
+
+bool
+g ()
+{
+  bool b = arr1 == arr2; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 != arr2; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 > arr2; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 >= arr2; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 < arr2; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+  b &= arr1 <= arr2; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+#ifdef __cplusplus
+  b &= +arr1 == +arr2;
+  b &= +arr1 != +arr2;
+  b &= +arr1 > +arr2;
+  b &= +arr1 >= +arr2;
+  b &= +arr1 < +arr2;
+  b &= +arr1 <= +arr2;
+#endif
+  b &= &arr1[0] == &arr2[0];
+  b &= &arr1[0] != &arr2[0];
+  b &= &arr1[0] > &arr2[0];
+  b &= &arr1[0] >= &arr2[0];
+  b &= &arr1[0] < &arr2[0];
+  b &= &arr1[0] <= &arr2[0];
+
+  b &= arr3 == arr4; /* { dg-warning "comparison between two arrays" "" { target { c++20 && c++23_down } } } */
+/* { dg-error "comparison between two arrays" "" { target c++26 } .-1 } */
+
+#if defined(__cplusplus) && __cplusplus > 201703L
+  auto cmp = arr1 <=> arr2; /* { dg-error "invalid operands" "" { target c++20 } } */
+#endif
+  return b;
+}
diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr15791-1.C b/gcc/testsuite/g++.dg/tree-ssa/pr15791-1.C
index 9905851ee7c..8a18f013ff4 100644
--- a/gcc/testsuite/g++.dg/tree-ssa/pr15791-1.C
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr15791-1.C
@@ -13,7 +13,7 @@  int main ()
     link_error ();
   if (b == &b[2])
     link_error ();
-  if (b != b)
+  if (b != b)  // { dg-error "comparison between two arrays" "" { target c++26 } }
     link_error ();
   if (&x.b[1] == &x.b[0])
     link_error ();