c++: duplicated side effects of xobj arg [PR113640]
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Commit Message
Bootstrapped and regtested on x86_64-pc-linu-xgnu, does this
look OK for trunk?
-- >8 --
We miscompile the below testcase because keep_unused_object_arg
duplicates the side effects of a (by-value) object argument of a
xobj member function.
PR c++/113640
gcc/cp/ChangeLog:
* call.cc (keep_unused_object_arg): Punt for an xobj member
function.
gcc/testsuite/ChangeLog:
* g++.dg/cpp23/explicit-obj-lambda14.C: New test.
---
gcc/cp/call.cc | 2 +-
.../g++.dg/cpp23/explicit-obj-lambda14.C | 27 +++++++++++++++++++
2 files changed, 28 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda14.C
Comments
On 1/30/24 10:09, Patrick Palka wrote:
> Bootstrapped and regtested on x86_64-pc-linu-xgnu, does this
> look OK for trunk?
OK.
> -- >8 --
>
> We miscompile the below testcase because keep_unused_object_arg
> duplicates the side effects of a (by-value) object argument of a
> xobj member function.
>
> PR c++/113640
>
> gcc/cp/ChangeLog:
>
> * call.cc (keep_unused_object_arg): Punt for an xobj member
> function.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp23/explicit-obj-lambda14.C: New test.
> ---
> gcc/cp/call.cc | 2 +-
> .../g++.dg/cpp23/explicit-obj-lambda14.C | 27 +++++++++++++++++++
> 2 files changed, 28 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda14.C
>
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index 9de0d77c423..451a189f7cf 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -5256,7 +5256,7 @@ keep_unused_object_arg (tree result, tree obj, tree fn)
> {
> if (result == NULL_TREE
> || result == error_mark_node
> - || TREE_CODE (TREE_TYPE (fn)) == METHOD_TYPE
> + || DECL_OBJECT_MEMBER_FUNCTION_P (fn)
> || !TREE_SIDE_EFFECTS (obj))
> return result;
>
> diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda14.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda14.C
> new file mode 100644
> index 00000000000..03dededfe33
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda14.C
> @@ -0,0 +1,27 @@
> +// PR c++/113640
> +// { dg-do run { target c++23 } }
> +
> +static int total;
> +
> +struct A {
> + A f(this auto self, int n) {
> + total += n;
> + return self;
> + }
> +};
> +
> +int main() {
> + A a;
> + a.f(1).f(42).f(100);
> + if (total != 143)
> + __builtin_abort();
> +
> + total = 0;
> + auto l = [](this auto self, int n) {
> + total += n;
> + return self;
> + };
> + l(1)(42)(100);
> + if (total != 143)
> + __builtin_abort();
> +}
@@ -5256,7 +5256,7 @@ keep_unused_object_arg (tree result, tree obj, tree fn)
{
if (result == NULL_TREE
|| result == error_mark_node
- || TREE_CODE (TREE_TYPE (fn)) == METHOD_TYPE
+ || DECL_OBJECT_MEMBER_FUNCTION_P (fn)
|| !TREE_SIDE_EFFECTS (obj))
return result;
new file mode 100644
@@ -0,0 +1,27 @@
+// PR c++/113640
+// { dg-do run { target c++23 } }
+
+static int total;
+
+struct A {
+ A f(this auto self, int n) {
+ total += n;
+ return self;
+ }
+};
+
+int main() {
+ A a;
+ a.f(1).f(42).f(100);
+ if (total != 143)
+ __builtin_abort();
+
+ total = 0;
+ auto l = [](this auto self, int n) {
+ total += n;
+ return self;
+ };
+ l(1)(42)(100);
+ if (total != 143)
+ __builtin_abort();
+}