Re: [PATCH] c++, v2: Implement CWG 2654 - Un-deprecation of compound volatile assignments

Tue, 15 Nov 2022 15:25:49 -0800 

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  <ja...@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

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