On Mon, Aug 15, 2022 at 12:31:10PM +0200, Jakub Jelinek wrote:
> Hi!
>
> From what I can see, this has been voted in as a DR and as it means
> we warn less often than before in -std={gnu,c}++2{0,3} modes or with
> -Wvolatile, I wonder if it shouldn't be backported to affected release
> branches as well.
I'd say so.
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Can't approve but LGTM.
> 2022-08-15 Jakub Jelinek <ja...@redhat.com>
>
> * typeck.cc (cp_build_modify_expr): Implement
> P2327R1 - De-deprecating volatile compound operations. Don't warn
> for |=, &= or ^= with volatile lhs.
> * expr.cc (mark_use) <case MODIFY_EXPR>: Adjust warning wording,
> leave out simple.
>
> * g++.dg/cpp2a/volatile1.C: Adjust for de-deprecation of volatile
> compound |=, &= and ^= operations.
> * g++.dg/cpp2a/volatile3.C: Likewise.
> * g++.dg/cpp2a/volatile5.C: Likewise.
>
> --- gcc/cp/typeck.cc.jj 2022-06-17 17:36:19.689107831 +0200
> +++ gcc/cp/typeck.cc 2022-08-14 11:14:15.368316963 +0200
> @@ -9136,10 +9136,14 @@ cp_build_modify_expr (location_t loc, tr
>
> /* An expression of the form E1 op= E2. [expr.ass] says:
> "Such expressions are deprecated if E1 has volatile-qualified
> - type." We warn here rather than in cp_genericize_r because
> + 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 (TREE_THIS_VOLATILE (lhs) || CP_TYPE_VOLATILE_P (lhstype))
> + 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");
> --- gcc/cp/expr.cc.jj 2022-06-27 11:18:02.268063761 +0200
> +++ gcc/cp/expr.cc 2022-08-14 11:41:37.555649422 +0200
> @@ -220,7 +220,7 @@ mark_use (tree expr, bool rvalue_p, bool
> case MODIFY_EXPR:
> {
> tree lhs = TREE_OPERAND (expr, 0);
> - /* [expr.ass] "A simple assignment whose left operand is of
> + /* [expr.ass] "An assignment whose left operand is of
> a volatile-qualified type is deprecated unless the assignment
> is either a discarded-value expression or appears in an
> unevaluated context." */
> @@ -230,7 +230,7 @@ mark_use (tree expr, bool rvalue_p, bool
> && !TREE_THIS_VOLATILE (expr))
> {
> if (warning_at (location_of (expr), OPT_Wvolatile,
> - "using value of simple assignment with "
> + "using value of assignment with "
> "%<volatile%>-qualified left operand is "
> "deprecated"))
> /* Make sure not to warn about this assignment again. */
> --- gcc/testsuite/g++.dg/cpp2a/volatile1.C.jj 2020-07-28 15:39:10.013756159
> +0200
> +++ gcc/testsuite/g++.dg/cpp2a/volatile1.C 2022-08-14 11:46:42.721626890
> +0200
> @@ -56,6 +56,9 @@ fn2 ()
> vi = i;
> vi = i = 42;
> i = vi = 42; // { dg-warning "assignment with .volatile.-qualified left
> operand is deprecated" "" { target c++20 } }
> + i = vi |= 42; // { dg-warning "using value of assignment with
> .volatile.-qualified left operand is deprecated" "" { target c++20 } }
> + i = vi &= 42; // { dg-warning "using value of assignment with
> .volatile.-qualified left operand is deprecated" "" { target c++20 } }
> + i = vi ^= 42; // { dg-warning "using value of 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 = 42, 45);
> (i = vi = 42, 10); // { dg-warning "assignment with .volatile.-qualified
> left operand is deprecated" "" { target c++20 } }
> @@ -74,8 +77,9 @@ fn2 ()
> 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-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-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 } }
> vi += vi = 42; // { dg-warning "assignment with .volatile.-qualified left
> operand is deprecated" "" { target c++20 } }
> @@ -131,7 +135,8 @@ 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-warning "assignment with .volatile.-qualified left
> operand is deprecated" "" { target c++20 } }
> + t &= 42; // { dg-bogus "assignment with .volatile.-qualified left operand
> is deprecated" }
> }
>
> void
> --- gcc/testsuite/g++.dg/cpp2a/volatile3.C.jj 2020-01-12 11:54:37.149402305
> +0100
> +++ gcc/testsuite/g++.dg/cpp2a/volatile3.C 2022-08-14 11:47:05.691324132
> +0200
> @@ -57,6 +57,9 @@ fn2 ()
> vi = i;
> vi = i = 42;
> i = vi = 42; // { dg-warning "assignment with .volatile.-qualified left
> operand is deprecated" }
> + i = vi |= 42; // { dg-warning "using value of assignment with
> .volatile.-qualified left operand is deprecated" }
> + i = vi &= 42; // { dg-warning "using value of assignment with
> .volatile.-qualified left operand is deprecated" }
> + i = vi ^= 42; // { dg-warning "using value of assignment with
> .volatile.-qualified left operand is deprecated" }
> &(vi = i); // { dg-warning "assignment with .volatile.-qualified left
> operand is deprecated" }
> (vi = 42, 45);
> (i = vi = 42, 10); // { dg-warning "assignment with .volatile.-qualified
> left operand is deprecated" }
> @@ -75,8 +78,9 @@ fn2 ()
> 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-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-warning "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" }
> @@ -132,7 +136,8 @@ 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-warning "assignment with .volatile.-qualified left
> operand is deprecated" }
> + t &= 42; // { dg-bogus "assignment with .volatile.-qualified left operand
> is deprecated" }
> }
>
> void
> --- gcc/testsuite/g++.dg/cpp2a/volatile5.C.jj 2021-02-08 19:07:33.110166905
> +0100
> +++ gcc/testsuite/g++.dg/cpp2a/volatile5.C 2022-08-14 11:42:47.779723765
> +0200
> @@ -8,8 +8,8 @@ f (bool b)
> {
> (b ? x : y) = 1;
> (b ? x : y) += 1; // { dg-warning "compound assignment" "" { target c++20
> } }
> - z = (b ? x : y) = 1; // { dg-warning "using value of simple assignment" ""
> { target c++20 } }
> - ((z = 2) ? x : y) = 1; // { dg-warning "using value of simple assignment"
> "" { target c++20 } }
> - (b ? (x = 2) : y) = 1; // { dg-warning "using value of simple assignment"
> "" { target c++20 } }
> - (b ? x : (y = 5)) = 1; // { dg-warning "using value of simple assignment"
> "" { target c++20 } }
> + 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 } }
> + (b ? x : (y = 5)) = 1; // { dg-warning "using value of assignment" "" {
> target c++20 } }
> }
>
> Jakub
>
Marek
