On Tue, 15 Feb 2022 at 13:13, Jason Merrill <ja...@redhat.com> wrote:
>
> On 2/14/22 21:30, Zhao Wei Liew wrote:
> > On 14/02/2022, Jason Merrill <ja...@redhat.com> wrote:
> >>>
> >>> +/* Returns true if EXPR is a reference to an implicit
> >>> + call to operator=(). */
> >>> +static bool
> >>> +is_assignment_overload_ref_p (tree expr)
> >>> +{
> >>> + if (expr == NULL_TREE || !REFERENCE_REF_P (expr))
> >>> + return false;
> >>
> >> This will only warn about op= that returns a reference, which is not
> >> required.
> >>
> >
> > Ah I understand now. I added some new test cases for non-reference return
> > types
> > and copied some code from extract_call_expr that seems to do what we want.
>
> Good plan, but let's call extract_call_expr rather than copy from it.
>
I agree. However, I can't seem to call extract_call_expr directly
because it calls gcc_assert
to assert that the resulting expression is a CALL_EXPR or AGGR_INIT_EXPR.
Instead, I've extracted the non-assert-related code into a
extract_call_expr_noassert function
and called that instead in the new patch. Is that okay?
> > --- a/gcc/cp/semantics.cc
> > +++ b/gcc/cp/semantics.cc
> > @@ -815,6 +815,33 @@ finish_goto_stmt (tree destination)
> > return add_stmt (build_stmt (input_location, GOTO_EXPR, destination));
> > }
> >
> > +/* Returns true if CALL is a (possibly wrapped) CALL_EXPR
> > + to operator=() that is written as an operator expression. */
> > +static bool
> > +is_assignment_op_expr_p(tree call)
>
> Missing space before (
>
Thanks the catch. I've fixed that in the latest patch.
As always, thanks so much for your feedback!
------Everything below is v5 of the patch------
When compiling the following code with g++ -Wparentheses, GCC does not
warn on the if statement. For example, there is no warning for this code:
struct A {
A& operator=(int);
operator bool();
};
void f(A a) {
if (a = 0); // no warning
}
This is because a = 0 is a call to operator=, which GCC does not handle.
This patch fixes this issue by handling calls to operator= when deciding
to warn.
Bootstrapped and tested on x86_64-unknown-linux-gnu.
v4: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590379.html
Changes since v4:
1. Refactor the non-assert-related code out of extract_call_expr and
call that function instead to check for call expressions.
v3: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590310.html
Changes since v3:
1. Also handle COMPOUND_EXPRs and TARGET_EXPRs.
v2: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590236.html
Changes since v2:
1. Add more test cases in Wparentheses-31.C.
2. Refactor added logic to a function (is_assignment_overload_ref_p).
3. Use REFERENCE_REF_P instead of INDIRECT_REF_P.
v1: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590158.html
Changes since v1:
1. Use CALL_EXPR_OPERATOR_SYNTAX to avoid warnings for explicit
operator=() calls.
2. Use INDIRECT_REF_P to filter implicit operator=() calls.
3. Use cp_get_callee_fndecl_nofold.
4. Add spaces before (.
PR c/25689
gcc/cp/ChangeLog:
* call.cc (extract_call_expr): Refactor non-assert code to
extract_call_expr_noassert.
(extract_call_expr_noassert): Refactor non-assert code.
* cp-tree.h (extract_call_expr_noassert): Add prototype.
* semantics.cc (is_assignment_op_expr_p): Add function to check
if an expression is a call to an op= operator expression.
(maybe_convert_cond): Handle the case of a op= operator expression
for the -Wparentheses diagnostic.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wparentheses-31.C: New test.
---
gcc/cp/call.cc | 11 +++-
gcc/cp/cp-tree.h | 1 +
gcc/cp/semantics.cc | 22 +++++++-
gcc/testsuite/g++.dg/warn/Wparentheses-31.C | 62 +++++++++++++++++++++
4 files changed, 94 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wparentheses-31.C
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index d6eed5ed83510..bead9d6b624c5 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7059,7 +7059,7 @@ build_op_subscript (const op_location_t &loc, tree obj,
convert_from_reference. */
tree
-extract_call_expr (tree call)
+extract_call_expr_noassert (tree call)
{
while (TREE_CODE (call) == COMPOUND_EXPR)
call = TREE_OPERAND (call, 1);
@@ -7090,6 +7090,15 @@ extract_call_expr (tree call)
default:;
}
+ return call;
+}
+
+/* Like extract_call_expr_noassert, but also asserts that
+ the extracted expression is indeed a call expression. */
+tree
+extract_call_expr (tree call)
+{
+ call = extract_call_expr_noassert (call);
gcc_assert (TREE_CODE (call) == CALL_EXPR
|| TREE_CODE (call) == AGGR_INIT_EXPR
|| call == error_mark_node);
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index f253b32c3f21d..19a7a9d2c9334 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6519,6 +6519,7 @@ extern bool null_ptr_cst_p (tree);
extern bool null_member_pointer_value_p (tree);
extern bool sufficient_parms_p (const_tree);
extern tree type_decays_to (tree);
+extern tree extract_call_expr_noassert (tree);
extern tree extract_call_expr (tree);
extern tree build_trivial_dtor_call (tree, bool = false);
extern bool ref_conv_binds_directly_p (tree, tree);
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 0cb17a6a8ab1c..008e554273aa3 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -815,6 +815,26 @@ finish_goto_stmt (tree destination)
return add_stmt (build_stmt (input_location, GOTO_EXPR, destination));
}
+/* Returns true if CALL is a (possibly wrapped) CALL_EXPR or AGGR_INIT_EXPR
+ to operator=() that is written as an operator expression. */
+static bool
+is_assignment_op_expr_p (tree call)
+{
+ if (call == NULL_TREE)
+ return false;
+
+ call = extract_call_expr_noassert (call);
+ if (call == NULL_TREE
+ || (TREE_CODE (call) != CALL_EXPR && TREE_CODE (call) != AGGR_INIT_EXPR)
+ || !CALL_EXPR_OPERATOR_SYNTAX (call))
+ return false;
+
+ tree fndecl = cp_get_callee_fndecl_nofold (call);
+ return fndecl != NULL_TREE
+ && DECL_ASSIGNMENT_OPERATOR_P (fndecl)
+ && DECL_OVERLOADED_OPERATOR_IS (fndecl, NOP_EXPR);
+}
+
/* COND is the condition-expression for an if, while, etc.,
statement. Convert it to a boolean value, if appropriate.
In addition, verify sequence points if -Wsequence-point is enabled. */
@@ -836,7 +856,7 @@ maybe_convert_cond (tree cond)
/* Do the conversion. */
cond = convert_from_reference (cond);
- if (TREE_CODE (cond) == MODIFY_EXPR
+ if ((TREE_CODE (cond) == MODIFY_EXPR || is_assignment_op_expr_p (cond))
&& warn_parentheses
&& !warning_suppressed_p (cond, OPT_Wparentheses)
&& warning_at (cp_expr_loc_or_input_loc (cond),
diff --git a/gcc/testsuite/g++.dg/warn/Wparentheses-31.C
b/gcc/testsuite/g++.dg/warn/Wparentheses-31.C
new file mode 100644
index 0000000000000..8d48ca5205782
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-31.C
@@ -0,0 +1,62 @@
+/* Test that -Wparentheses warns for struct/class assignments,
+ except for explicit calls to operator= (). */
+/* PR c/25689 */
+/* { dg-options "-Wparentheses" } */
+
+struct A
+{
+ A& operator= (int);
+ A operator= (double);
+ operator bool ();
+};
+
+struct B
+{
+ bool x;
+ B& operator= (int);
+ B operator= (double);
+ operator bool ();
+};
+
+struct C
+{
+ C& operator= (int);
+ virtual C operator= (double);
+ operator bool ();
+};
+
+/* Test empty class */
+void f1 (A a1, A a2)
+{
+ if (a1 = 0); /* { dg-warning "suggest parentheses" } */
+ if (a1 = 0.); /* { dg-warning "suggest parentheses" } */
+ if (a1.operator= (0));
+ if (a1.operator= (a2));
+
+ /* Ideally, we'd warn for empty classes using trivial operator= (below),
+ but we don't do so yet as it is a non-trivial COMPOUND_EXPR. */
+ // if (a1 = a2);
+}
+
+/* Test non-empty class */
+void f2(B b1, B b2)
+{
+ if (b1 = 0); /* { dg-warning "suggest parentheses" } */
+ if (b1 = 0.); /* { dg-warning "suggest parentheses" } */
+ if (b1 = b2); /* { dg-warning "suggest parentheses" } */
+ if (b1.operator= (0));
+
+ /* Ideally, we wouldn't warn for non-empty classes using trivial
+ operator= (below), but we currently do as it is a MODIFY_EXPR. */
+ // if (b1.operator= (b2));
+}
+
+/* Test class with vtable */
+void f3(C c1, C c2)
+{
+ if (c1 = 0); /* { dg-warning "suggest parentheses" } */
+ if (c1 = 0.); /* { dg-warning "suggest parentheses" } */
+ if (c1 = c2); /* { dg-warning "suggest parentheses" } */
+ if (c1.operator= (0));
+ if (c1.operator= (c2));
+}
--
2.35.1
