* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
@ 2022-02-16 7:16 Zhao Wei Liew
2022-02-16 16:59 ` Jason Merrill
0 siblings, 1 reply; 7+ messages in thread
From: Zhao Wei Liew @ 2022-02-16 7:16 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
[-- Attachment #1: Type: text/plain, Size: 3160 bytes --]
Before I start, sincere apologies for the email mishaps! I was setting up
an email client and somehow the emails I sent did not initially seem to
go through, but they actually did. You might have received several
duplicate emails as a result.
On Wed Feb 16, 2022 at 4:06 AM +08, Jason Merrill wrote:
> > Ah, I see. I found it a bit odd that gcc-commit-mklog auto-generated a
> > subject with "c:",
> > but I just went with it as I didn't know any better. Unfortunately, I
> > can't change it now on the current thread.
>
> That came from this line in the testcase:
>
> > +/* PR c/25689 */
>
> The PR should be c++/25689. Also, sometimes the bugzilla component
> isn't the same as the area of the compiler you're changing; the latter
> is what you want in the patch subject, so that the right people know to
> review it.
Oh, I see. Thanks for the explanation. I've fixed the line.
> > Ah, I didn't notice that. Sorry about that! I'm kinda new to the whole
> > mailing list setup so there are some kinks I have to iron out.
>
> FWIW it's often easier to send the patch as an attachment.
Alright, I'll send patches as attachments instead. I originally sent
them as text as it is easier to comment on them.
> > +/* 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));
>
> You can avoid it by calling suppress_warning on that MODIFY_EXPR in
> build_over_call.
Unfortunately, that also affects the warning for if (b1 = b2) just 5
lines above. Both expressions seem to generate the same tree structure.
v6: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590419.html
1. Check for error_mark_node in is_assignment_op_expr_pr.
2. Change "c:" to "c++:".
v5: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590393.html
Changes since v5:
1. Revert changes in v4.
2. Replace gcc_assert with a return NULL_TREE in extract_call_expr.
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 (.
[-- Attachment #2: 0001-c-Add-diagnostic-when-operator-is-used-as-truth-cond.patch --]
[-- Type: application/x-patch, Size: 5231 bytes --]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
2022-02-16 7:16 [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689] Zhao Wei Liew
@ 2022-02-16 16:59 ` Jason Merrill
2022-02-18 0:32 ` Zhao Wei Liew
0 siblings, 1 reply; 7+ messages in thread
From: Jason Merrill @ 2022-02-16 16:59 UTC (permalink / raw)
To: Zhao Wei Liew; +Cc: GCC Patches
On 2/16/22 02:16, Zhao Wei Liew wrote:
> On Wed Feb 16, 2022 at 4:06 AM +08, Jason Merrill wrote:
>>> Ah, I see. I found it a bit odd that gcc-commit-mklog auto-generated a
>>> subject with "c:",
>>> but I just went with it as I didn't know any better. Unfortunately, I
>>> can't change it now on the current thread.
>>
>> That came from this line in the testcase:
>>
>> > +/* PR c/25689 */
>>
>> The PR should be c++/25689. Also, sometimes the bugzilla component
>> isn't the same as the area of the compiler you're changing; the latter
>> is what you want in the patch subject, so that the right people know to
>> review it.
>
> Oh, I see. Thanks for the explanation. I've fixed the line.
>
>>> Ah, I didn't notice that. Sorry about that! I'm kinda new to the whole
>>> mailing list setup so there are some kinks I have to iron out.
>>
>> FWIW it's often easier to send the patch as an attachment.
>
> Alright, I'll send patches as attachments instead. I originally sent
> them as text as it is easier to comment on them.
It is a bit more of a hassle in this case because your mail sender
doesn't mark the patch as text, but rather application/mbox or
application/x-patch, so my mail reader for patch review (Thunderbird)
doesn't display it inline. I tried sending myself a patch through the
gmail web interface, and it used text/x-patch, which is OK; what are you
using to send?
Maybe renaming the file to .txt before sending would help?
>>> +/* 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));
>>
>> You can avoid it by calling suppress_warning on that MODIFY_EXPR in
>> build_over_call.
>
> Unfortunately, that also affects the warning for if (b1 = b2) just 5
> lines above. Both expressions seem to generate the same tree structure.
True, you would need to put the call to suppress_warning in build_new_op
around where CALL_EXPR_OPERATOR_SYNTAX is set.
Jason
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
2022-02-16 16:59 ` Jason Merrill
@ 2022-02-18 0:32 ` Zhao Wei Liew
2022-02-18 3:30 ` Zhao Wei Liew
0 siblings, 1 reply; 7+ messages in thread
From: Zhao Wei Liew @ 2022-02-18 0:32 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
On Thu, 17 Feb 2022 at 00:59, Jason Merrill <jason@redhat.com> wrote:
>
> On 2/16/22 02:16, Zhao Wei Liew wrote:
> > On Wed Feb 16, 2022 at 4:06 AM +08, Jason Merrill wrote:
> >>> Ah, I see. I found it a bit odd that gcc-commit-mklog auto-generated a
> >>> subject with "c:",
> >>> but I just went with it as I didn't know any better. Unfortunately, I
> >>> can't change it now on the current thread.
> >>
> >> That came from this line in the testcase:
> >>
> >> > +/* PR c/25689 */
> >>
> >> The PR should be c++/25689. Also, sometimes the bugzilla component
> >> isn't the same as the area of the compiler you're changing; the latter
> >> is what you want in the patch subject, so that the right people know to
> >> review it.
> >
> > Oh, I see. Thanks for the explanation. I've fixed the line.
> >
> >>> Ah, I didn't notice that. Sorry about that! I'm kinda new to the whole
> >>> mailing list setup so there are some kinks I have to iron out.
> >>
> >> FWIW it's often easier to send the patch as an attachment.
> >
> > Alright, I'll send patches as attachments instead. I originally sent
> > them as text as it is easier to comment on them.
>
> It is a bit more of a hassle in this case because your mail sender
> doesn't mark the patch as text, but rather application/mbox or
> application/x-patch, so my mail reader for patch review (Thunderbird)
> doesn't display it inline. I tried sending myself a patch through the
> gmail web interface, and it used text/x-patch, which is OK; what are you
> using to send?
>
> Maybe renaming the file to .txt before sending would help?
Hmm, in the end I used gmail to send the patch, so I'm not sure why it was
marked that way. I'll test it out again before sending another patch.
> >>> +/* 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));
> >>
> >> You can avoid it by calling suppress_warning on that MODIFY_EXPR in
> >> build_over_call.
> >
> > Unfortunately, that also affects the warning for if (b1 = b2) just 5
> > lines above. Both expressions seem to generate the same tree structure.
>
> True, you would need to put the call to suppress_warning in build_new_op
> around where CALL_EXPR_OPERATOR_SYNTAX is set.
It seems like that would suppress the warning for the case of if (b1 = b2)
instead of
if (b1.operator= (b2)). Do you mean to add the call to suppress_warning
in build_method_call instead?
This is what I've tried so far:
1. Call suppress_warning (result, ...) in the trivial_fn_p block in
build_new_op,
right above the comment "There won't be a CALL_EXPR" (line 6699).
This suppresses the warning for if (b1 = b2) but not for if
(b1.operator= (b2)).
2. Call suppress_warning (result, ...) in build_method_call, right after
the call to
build_over_call (line 11141). This suppresses the warning for if
(b1.operator= (b2))
and not if (b1 = b2).
Based on this, I think the 2nd option might be what we want here? Please
correct me if I'm
wrong. I'm also unsure if there are issues that might arise with this
change.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
2022-02-18 0:32 ` Zhao Wei Liew
@ 2022-02-18 3:30 ` Zhao Wei Liew
2022-03-11 22:15 ` Jason Merrill
0 siblings, 1 reply; 7+ messages in thread
From: Zhao Wei Liew @ 2022-02-18 3:30 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
[-- Attachment #1: Type: text/plain, Size: 3407 bytes --]
On Fri, 18 Feb 2022 at 08:32, Zhao Wei Liew <zhaoweiliew@gmail.com> wrote:
>
> > >>> +/* 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));
> > >>
> > >> You can avoid it by calling suppress_warning on that MODIFY_EXPR in
> > >> build_over_call.
> > >
> > > Unfortunately, that also affects the warning for if (b1 = b2) just 5
> > > lines above. Both expressions seem to generate the same tree structure.
> >
> > True, you would need to put the call to suppress_warning in build_new_op
> > around where CALL_EXPR_OPERATOR_SYNTAX is set.
>
> It seems like that would suppress the warning for the case of if (b1 = b2) instead of
> if (b1.operator= (b2)). Do you mean to add the call to suppress_warning
> in build_method_call instead?
>
> This is what I've tried so far:
>
> 1. Call suppress_warning (result, ...) in the trivial_fn_p block in build_new_op,
> right above the comment "There won't be a CALL_EXPR" (line 6699).
> This suppresses the warning for if (b1 = b2) but not for if (b1.operator= (b2)).
>
> 2. Call suppress_warning (result, ...) in build_method_call, right after the call to
> build_over_call (line 11141). This suppresses the warning for if (b1.operator= (b2))
> and not if (b1 = b2).
>
> Based on this, I think the 2nd option might be what we want here? Please correct me if I'm
> wrong. I'm also unsure if there are issues that might arise with this change.
To better illustrate the 2nd option, I've attached it as a patch v8.
How does it look?
v7: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590464.html
Changes since v7:
1. Suppress -Wparentheses warnings in build_new_method_call.
2. Uncomment the test case for if (b1.operator= (b2)).
v6: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590419.html
Changes since v6:
1. Check for error_mark_node in is_assignment_op_expr_pr.
2. Change "c:" to "c++:".
v5: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590393.html
Changes since v5:
1. Revert changes in v4.
2. Replace gcc_assert with a return NULL_TREE in extract_call_expr.
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 (.
[-- Attachment #2: 0001-c-Add-diagnostic-when-operator-is-used-as-truth-cond.patch --]
[-- Type: text/x-patch, Size: 5608 bytes --]
From ef4cfecca64b2cb199a5d3979fe99f8c9bd0f414 Mon Sep 17 00:00:00 2001
From: Zhao Wei Liew <zhaoweiliew@gmail.com>
Date: Tue, 15 Feb 2022 17:44:29 +0800
Subject: [PATCH] c++: Add diagnostic when operator= is used as truth cond
[PR25689]
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.
PR c++/25689
gcc/cp/ChangeLog:
* call.cc (extract_call_expr): Return a NULL_TREE on failure
instead of asserting.
* 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.
Signed-off-by: Zhao Wei Liew <zhaoweiliew@gmail.com>
---
gcc/cp/call.cc | 12 +++--
gcc/cp/semantics.cc | 22 +++++++-
gcc/testsuite/g++.dg/warn/Wparentheses-31.C | 59 +++++++++++++++++++++
3 files changed, 89 insertions(+), 4 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 d6eed5ed835..caf22e02b39 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7090,9 +7090,10 @@ extract_call_expr (tree call)
default:;
}
- gcc_assert (TREE_CODE (call) == CALL_EXPR
- || TREE_CODE (call) == AGGR_INIT_EXPR
- || call == error_mark_node);
+ if (TREE_CODE (call) != CALL_EXPR
+ && TREE_CODE (call) != AGGR_INIT_EXPR
+ && call != error_mark_node)
+ return NULL_TREE;
return call;
}
@@ -11137,6 +11138,11 @@ build_new_method_call (tree instance, tree fns, vec<tree, va_gc> **args,
*fn_p = fn;
/* Build the actual CALL_EXPR. */
call = build_over_call (cand, flags, complain);
+
+ /* Suppress warnings for if (my_struct.operator= (x)) where
+ my_struct is implicitly converted to bool. */
+ suppress_warning (call, OPT_Wparentheses);
+
/* In an expression of the form `a->f()' where `f' turns
out to be a static member function, `a' is
none-the-less evaluated. */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 0cb17a6a8ab..9cd88715417 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 (call);
+ if (call == NULL_TREE
+ || call == error_mark_node
+ || !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 00000000000..6b5ce3c0e6b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-31.C
@@ -0,0 +1,59 @@
+/* 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));
+ 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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
2022-02-18 3:30 ` Zhao Wei Liew
@ 2022-03-11 22:15 ` Jason Merrill
2022-03-13 23:43 ` Zhao Wei Liew
0 siblings, 1 reply; 7+ messages in thread
From: Jason Merrill @ 2022-03-11 22:15 UTC (permalink / raw)
To: Zhao Wei Liew; +Cc: GCC Patches
On 2/17/22 23:30, Zhao Wei Liew wrote:
> On Fri, 18 Feb 2022 at 08:32, Zhao Wei Liew <zhaoweiliew@gmail.com> wrote:
>>
>>>>>> +/* 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));
>>>>>
>>>>> You can avoid it by calling suppress_warning on that MODIFY_EXPR in
>>>>> build_over_call.
>>>>
>>>> Unfortunately, that also affects the warning for if (b1 = b2) just 5
>>>> lines above. Both expressions seem to generate the same tree structure.
>>>
>>> True, you would need to put the call to suppress_warning in build_new_op
>>> around where CALL_EXPR_OPERATOR_SYNTAX is set.
>>
>> It seems like that would suppress the warning for the case of if (b1 = b2) instead of
>> if (b1.operator= (b2)). Do you mean to add the call to suppress_warning
>> in build_method_call instead?
>>
>> This is what I've tried so far:
>>
>> 1. Call suppress_warning (result, ...) in the trivial_fn_p block in build_new_op,
>> right above the comment "There won't be a CALL_EXPR" (line 6699).
>> This suppresses the warning for if (b1 = b2) but not for if (b1.operator= (b2)).
>>
>> 2. Call suppress_warning (result, ...) in build_method_call, right after the call to
>> build_over_call (line 11141). This suppresses the warning for if (b1.operator= (b2))
>> and not if (b1 = b2).
>>
>> Based on this, I think the 2nd option might be what we want here? Please correct me if I'm
>> wrong. I'm also unsure if there are issues that might arise with this change.
>
> To better illustrate the 2nd option, I've attached it as a patch v8.
> How does it look?
It looks good, but unfortunately regresses some other warning tests,
such as Wnonnull5.C. Please remember to run the regression tests before
sending a patch (https://gcc.gnu.org/contribute.html#testing).
This seems to be a complicated problem with suppress_warning, which
means your call to suppress_warning effectively silences all later
warnings, not just -Wparentheses.
You should be able to work around this issue by only calling
suppress_warning in the specific case we're interested in, i.e. when
warn_parentheses is enabled and "call" is a MODIFY_EXPR.
> v7: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590464.html
> Changes since v7:
> 1. Suppress -Wparentheses warnings in build_new_method_call.
> 2. Uncomment the test case for if (b1.operator= (b2)).
>
> v6: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590419.html
> Changes since v6:
> 1. Check for error_mark_node in is_assignment_op_expr_pr.
> 2. Change "c:" to "c++:".
>
> v5: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590393.html
> Changes since v5:
> 1. Revert changes in v4.
> 2. Replace gcc_assert with a return NULL_TREE in extract_call_expr.
>
> 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 (.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
2022-03-11 22:15 ` Jason Merrill
@ 2022-03-13 23:43 ` Zhao Wei Liew
2022-03-24 22:12 ` Jason Merrill
0 siblings, 1 reply; 7+ messages in thread
From: Zhao Wei Liew @ 2022-03-13 23:43 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
[-- Attachment #1: Type: text/plain, Size: 2456 bytes --]
On Sat, 12 Mar 2022 at 06:15, Jason Merrill <jason@redhat.com> wrote:
> It looks good, but unfortunately regresses some other warning tests,
> such as Wnonnull5.C. Please remember to run the regression tests before
> sending a patch (https://gcc.gnu.org/contribute.html#testing).
>
> This seems to be a complicated problem with suppress_warning, which
> means your call to suppress_warning effectively silences all later
> warnings, not just -Wparentheses.
>
> You should be able to work around this issue by only calling
> suppress_warning in the specific case we're interested in, i.e. when
> warn_parentheses is enabled and "call" is a MODIFY_EXPR.
My apologies. I've fixed the issue as you suggested and run the regression tests
to ensure no test regressions. The new patch (v9) is attached.
v8: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590570.html
Changes since v8:
1. Fix a test regression by calling suppress_warning only when "call"
is a MODIFY_EXPR.
v7: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590464.html
Changes since v7:
1. Suppress -Wparentheses warnings in build_new_method_call.
2. Uncomment the test case for if (b1.operator= (b2)).
v6: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590419.html
Changes since v6:
1. Check for error_mark_node in is_assignment_op_expr_pr.
2. Change "c:" to "c++:".
v5: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590393.html
Changes since v5:
1. Revert changes in v4.
2. Replace gcc_assert with a return NULL_TREE in extract_call_expr.
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 (.
[-- Attachment #2: 0001-c-Add-diagnostic-when-operator-is-used-as-truth-cond.patch.txt --]
[-- Type: text/plain, Size: 5745 bytes --]
From 28f884d51a56889e84acba970a5aac9da8b24d99 Mon Sep 17 00:00:00 2001
From: Zhao Wei Liew <zhaoweiliew@gmail.com>
Date: Tue, 15 Feb 2022 17:44:29 +0800
Subject: [PATCH] c++: Add diagnostic when operator= is used as truth cond
[PR25689]
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 regression tested on x86_64-pc-linux-gnu.
PR c++/25689
gcc/cp/ChangeLog:
* call.cc (extract_call_expr): Return a NULL_TREE on failure
instead of asserting.
(build_new_method_call): Suppress -Wparentheses diagnostic for
MODIFY_EXPR.
* 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.
Signed-off-by: Zhao Wei Liew <zhaoweiliew@gmail.com>
---
gcc/cp/call.cc | 13 +++--
gcc/cp/semantics.cc | 22 +++++++-
gcc/testsuite/g++.dg/warn/Wparentheses-31.C | 59 +++++++++++++++++++++
3 files changed, 90 insertions(+), 4 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 8fe8ef306ea..f502251c291 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -7101,9 +7101,10 @@ extract_call_expr (tree call)
default:;
}
- gcc_assert (TREE_CODE (call) == CALL_EXPR
- || TREE_CODE (call) == AGGR_INIT_EXPR
- || call == error_mark_node);
+ if (TREE_CODE (call) != CALL_EXPR
+ && TREE_CODE (call) != AGGR_INIT_EXPR
+ && call != error_mark_node)
+ return NULL_TREE;
return call;
}
@@ -11148,6 +11149,12 @@ build_new_method_call (tree instance, tree fns, vec<tree, va_gc> **args,
*fn_p = fn;
/* Build the actual CALL_EXPR. */
call = build_over_call (cand, flags, complain);
+
+ /* Suppress warnings for if (my_struct.operator= (x)) where
+ my_struct is implicitly converted to bool. */
+ if (TREE_CODE (call) == MODIFY_EXPR)
+ suppress_warning (call, OPT_Wparentheses);
+
/* In an expression of the form `a->f()' where `f' turns
out to be a static member function, `a' is
none-the-less evaluated. */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index d5565ebe02d..06e1db6e49a 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 (call);
+ if (call == NULL_TREE
+ || call == error_mark_node
+ || !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 00000000000..6b5ce3c0e6b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-31.C
@@ -0,0 +1,59 @@
+/* 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));
+ 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));
+}
--
2.25.1
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v7] c++: Add diagnostic when operator= is used as truth cond [PR25689]
2022-03-13 23:43 ` Zhao Wei Liew
@ 2022-03-24 22:12 ` Jason Merrill
0 siblings, 0 replies; 7+ messages in thread
From: Jason Merrill @ 2022-03-24 22:12 UTC (permalink / raw)
To: Zhao Wei Liew; +Cc: GCC Patches
On 3/13/22 19:43, Zhao Wei Liew wrote:
> On Sat, 12 Mar 2022 at 06:15, Jason Merrill <jason@redhat.com> wrote:
>> It looks good, but unfortunately regresses some other warning tests,
>> such as Wnonnull5.C. Please remember to run the regression tests before
>> sending a patch (https://gcc.gnu.org/contribute.html#testing).
>>
>> This seems to be a complicated problem with suppress_warning, which
>> means your call to suppress_warning effectively silences all later
>> warnings, not just -Wparentheses.
>>
>> You should be able to work around this issue by only calling
>> suppress_warning in the specific case we're interested in, i.e. when
>> warn_parentheses is enabled and "call" is a MODIFY_EXPR.
>
> My apologies. I've fixed the issue as you suggested and run the regression tests
> to ensure no test regressions. The new patch (v9) is attached.
Looks good. One thing:
> + /* 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);
It would be better to uncomment this line and give it an xfailed
warning, i.e.
/* { dg-warning "suggest parentheses" "" { xfail *-*-* } } */
I've made this change and added the patch to my queue to commit when GCC
13 stage 1 opens, probably next month.
Thanks!
Jason
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-03-24 22:12 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2022-02-16 16:59 ` Jason Merrill
2022-02-18 0:32 ` Zhao Wei Liew
2022-02-18 3:30 ` Zhao Wei Liew
2022-03-11 22:15 ` Jason Merrill
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