c++, v2: Implement CWG 2654 - Un-deprecation of compound volatile assignments

  On Fri, Nov 11, 2022 at 08:43:04AM +0100, Jakub Jelinek wrote:
> 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?

Here is an updated patch that passed bootstrap/regtest, difference
is just a few further testsuite tweaks.

2022-11-13  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.
	* g++.dg/ext/vector25.C (foo): Don't expect a warning.
	* g++.dg/cpp1y/new1.C (test_unused): Likewise.



	Jakub
  

On 11/13/22 01:43, Jakub Jelinek wrote:
> On Fri, Nov 11, 2022 at 08:43:04AM +0100, Jakub Jelinek wrote:
>> 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?
> 
> Here is an updated patch that passed bootstrap/regtest, difference
> is just a few further testsuite tweaks.

OK.

> 2022-11-13  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.
> 	* g++.dg/ext/vector25.C (foo): Don't expect a warning.
> 	* g++.dg/cpp1y/new1.C (test_unused): 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 } }
> --- gcc/testsuite/g++.dg/ext/vector25.C.jj	2020-01-14 20:02:46.842608950 +0100
> +++ gcc/testsuite/g++.dg/ext/vector25.C	2022-11-12 09:18:20.654702399 +0100
> @@ -2,5 +2,5 @@ volatile int i __attribute__((vector_siz
>   
>   void foo()
>   {
> -  i += i; // { dg-warning "deprecated" "" { target c++2a } }
> +  i += i; // { dg-bogus "deprecated" }
>   }
> --- gcc/testsuite/g++.dg/cpp1y/new1.C.jj	2020-09-24 11:58:14.049056885 +0200
> +++ gcc/testsuite/g++.dg/cpp1y/new1.C	2022-11-12 09:16:49.349943682 +0100
> @@ -65,7 +65,7 @@ void
>   test_unused() {
>     volatile double d = 0.0;
>     double *p = new double ();
> -  d += 1.0; // { dg-warning "deprecated" "" { target c++2a } }
> +  d += 1.0;
>     delete p;
>   }
>   
> 
> 
> 	Jakub
>