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* [PATCH] c++: Implement CWG 2654 - Un-deprecation of compound volatile assignments
@ 2022-11-11  7:43 Jakub Jelinek
  2022-11-13 11:43 ` [PATCH] c++, v2: " Jakub Jelinek
  0 siblings, 1 reply; 3+ messages in thread
From: Jakub Jelinek @ 2022-11-11  7:43 UTC (permalink / raw)
  To: Jason Merrill; +Cc: gcc-patches

Hi!

Again, because stage1 close is near, posting the following patch
to implement CWG 2654.

Ok for trunk if it passes bootstrap/regtest and is voted into C++23
and C++20 as a DR?

2022-11-11  Jakub Jelinek  <jakub@redhat.com>

	* typeck.cc (cp_build_modify_expr): Implement CWG 2654
	- Un-deprecation of compound volatile assignments.  Remove
	-Wvolatile warning about compound volatile assignments.

	* g++.dg/cpp2a/volatile1.C (fn2, fn3, racoon): Adjust expected
	diagnostics.
	* g++.dg/cpp2a/volatile3.C (fn2, fn3, racoon): Likewise.
	* g++.dg/cpp2a/volatile5.C (f): Likewise.

--- gcc/cp/typeck.cc.jj	2022-11-09 11:22:42.617628059 +0100
+++ gcc/cp/typeck.cc	2022-11-10 23:19:00.394228067 +0100
@@ -9513,19 +9513,6 @@ cp_build_modify_expr (location_t loc, tr
 			 && MAYBE_CLASS_TYPE_P (TREE_TYPE (lhstype)))
 			|| MAYBE_CLASS_TYPE_P (lhstype)));
 
-	  /* An expression of the form E1 op= E2.  [expr.ass] says:
-	     "Such expressions are deprecated if E1 has volatile-qualified
-	     type and op is not one of the bitwise operators |, &, ^."
-	     We warn here rather than in cp_genericize_r because
-	     for compound assignments we are supposed to warn even if the
-	     assignment is a discarded-value expression.  */
-	  if (modifycode != BIT_AND_EXPR
-	      && modifycode != BIT_IOR_EXPR
-	      && modifycode != BIT_XOR_EXPR
-	      && (TREE_THIS_VOLATILE (lhs) || CP_TYPE_VOLATILE_P (lhstype)))
-	    warning_at (loc, OPT_Wvolatile,
-			"compound assignment with %<volatile%>-qualified left "
-			"operand is deprecated");
 	  /* Preevaluate the RHS to make sure its evaluation is complete
 	     before the lvalue-to-rvalue conversion of the LHS:
 
--- gcc/testsuite/g++.dg/cpp2a/volatile1.C.jj	2022-08-16 13:15:22.739043862 +0200
+++ gcc/testsuite/g++.dg/cpp2a/volatile1.C	2022-11-10 23:23:18.949717772 +0100
@@ -74,17 +74,17 @@ fn2 ()
   decltype(i = vi = 42) x3 = i;
 
   // Compound assignments.
-  vi += i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
-  vi -= i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
-  vi %= i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
+  vi += i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
+  vi -= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
+  vi %= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi ^= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi |= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi &= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
-  vi /= i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
+  vi /= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi = vi += 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
   vi += vi = 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
   i *= vi;
-  decltype(vi -= 42) x2 = vi; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
+  decltype(vi -= 42) x2 = vi; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 
   // Structured bindings.
   int a[] = { 10, 5 };
@@ -107,12 +107,12 @@ fn3 ()
   volatile U u;
   u.c = 42;
   i = u.c = 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
-  u.c += 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
+  u.c += 42; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 
   volatile T t;
   t.a = 3;
   j = t.a = 3; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
-  t.a += 3; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
+  t.a += 3; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 
   volatile int *src = &i;
   *src; // No assignment, don't warn.
@@ -135,7 +135,7 @@ void raccoon ()
   volatile T t, u;
   t = 42;
   u = t = 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
-  t += 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" "" { target c++20 } }
+  t += 42; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   t &= 42; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 }
 
--- gcc/testsuite/g++.dg/cpp2a/volatile3.C.jj	2022-08-16 13:15:22.753043682 +0200
+++ gcc/testsuite/g++.dg/cpp2a/volatile3.C	2022-11-10 23:24:24.781823998 +0100
@@ -75,17 +75,17 @@ fn2 ()
   decltype(i = vi = 42) x3 = i;
 
   // Compound assignments.
-  vi += i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
-  vi -= i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
-  vi %= i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
+  vi += i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
+  vi -= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
+  vi %= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi ^= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi |= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi &= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
-  vi /= i; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
+  vi /= i; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   vi = vi += 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
   vi += vi = 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
   i *= vi;
-  decltype(vi -= 42) x2 = vi; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
+  decltype(vi -= 42) x2 = vi; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 
   // Structured bindings.
   int a[] = { 10, 5 };
@@ -108,12 +108,12 @@ fn3 ()
   volatile U u;
   u.c = 42;
   i = u.c = 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
-  u.c += 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
+  u.c += 42; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 
   volatile T t;
   t.a = 3;
   j = t.a = 3; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
-  t.a += 3; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
+  t.a += 3; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 
   volatile int *src = &i;
   *src; // No assignment, don't warn.
@@ -136,7 +136,7 @@ void raccoon ()
   volatile T t, u;
   t = 42;
   u = t = 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
-  t += 42; // { dg-warning "assignment with .volatile.-qualified left operand is deprecated" }
+  t += 42; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
   t &= 42; // { dg-bogus "assignment with .volatile.-qualified left operand is deprecated" }
 }
 
--- gcc/testsuite/g++.dg/cpp2a/volatile5.C.jj	2022-08-16 13:15:22.778043359 +0200
+++ gcc/testsuite/g++.dg/cpp2a/volatile5.C	2022-11-10 23:25:07.445244776 +0100
@@ -7,7 +7,7 @@ void
 f (bool b)
 {
   (b ? x : y) = 1;
-  (b ? x : y) += 1; // { dg-warning "compound assignment" "" { target c++20 } }
+  (b ? x : y) += 1; // { dg-bogus "compound assignment" }
   z = (b ? x : y) = 1; // { dg-warning "using value of assignment" "" { target c++20 } }
   ((z = 2) ? x : y) = 1; // { dg-warning "using value of assignment" "" { target c++20 } }
   (b ? (x = 2) : y) = 1; // { dg-warning "using value of assignment" "" { target c++20 } }

	Jakub


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2022-11-11  7:43 [PATCH] c++: Implement CWG 2654 - Un-deprecation of compound volatile assignments Jakub Jelinek
2022-11-13 11:43 ` [PATCH] c++, v2: " Jakub Jelinek
2022-11-15 23:25   ` Jason Merrill

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