c++: Implement P2327R1 - De-deprecating volatile compound operations

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.

2022-08-16  Jakub Jelinek  <jakub@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.

diff --git a/gcc/cp/expr.cc b/gcc/cp/expr.cc
index 56fc11f..f3e155b 100644 (file)
--- a/gcc/cp/expr.cc
+++ b/gcc/cp/expr.cc
@@ -220,7 +220,7 @@ mark_use (tree expr, bool rvalue_p, bool read_p,
     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 read_p,
              && !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.  */

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 15548e5..6b38c8c 100644 (file)
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -9136,10 +9136,14 @@ cp_build_modify_expr (location_t loc, tree lhs, enum tree_code modifycode,
 
          /* 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");

diff --git a/gcc/testsuite/g++.dg/cpp2a/volatile1.C b/gcc/testsuite/g++.dg/cpp2a/volatile1.C
index 7ea6b47..a0264a4 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp2a/volatile1.C
+++ b/gcc/testsuite/g++.dg/cpp2a/volatile1.C
@@ -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

diff --git a/gcc/testsuite/g++.dg/cpp2a/volatile3.C b/gcc/testsuite/g++.dg/cpp2a/volatile3.C
index f10a297..58816dc 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp2a/volatile3.C
+++ b/gcc/testsuite/g++.dg/cpp2a/volatile3.C
@@ -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

diff --git a/gcc/testsuite/g++.dg/cpp2a/volatile5.C b/gcc/testsuite/g++.dg/cpp2a/volatile5.C
index 1f9d238..3684be9 100644 (file)
--- a/gcc/testsuite/g++.dg/cpp2a/volatile5.C
+++ b/gcc/testsuite/g++.dg/cpp2a/volatile5.C
@@ -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 } }
 }