* [PATCH] c++: -Wdangling-reference not suppressed in template [PR109774]
@ 2023-05-16 19:13 Marek Polacek
2023-05-16 19:35 ` Jason Merrill
0 siblings, 1 reply; 2+ messages in thread
From: Marek Polacek @ 2023-05-16 19:13 UTC (permalink / raw)
To: GCC Patches, Jason Merrill
In check_return_expr, we suppress the -Wdangling-reference warning when
we're sure it would be a false positive. It wasn't working in a
template, though, because the suppress_warning call was never reached.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk and 13.2?
PR c++/109774
gcc/cp/ChangeLog:
* typeck.cc (check_return_expr): In a template, return only after
suppressing -Wdangling-reference.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wdangling-reference13.C: New test.
---
gcc/cp/typeck.cc | 6 ++---
.../g++.dg/warn/Wdangling-reference13.C | 23 +++++++++++++++++++
2 files changed, 26 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wdangling-reference13.C
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 53ac925a092..c225c4e2423 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -11236,9 +11236,6 @@ check_return_expr (tree retval, bool *no_warning)
build_zero_cst (TREE_TYPE (retval)));
}
- if (processing_template_decl)
- return saved_retval;
-
/* A naive attempt to reduce the number of -Wdangling-reference false
positives: if we know that this function can return a variable with
static storage duration rather than one of its parameters, suppress
@@ -11250,6 +11247,9 @@ check_return_expr (tree retval, bool *no_warning)
&& TREE_STATIC (bare_retval))
suppress_warning (current_function_decl, OPT_Wdangling_reference);
+ if (processing_template_decl)
+ return saved_retval;
+
/* Actually copy the value returned into the appropriate location. */
if (retval && retval != result)
{
diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference13.C b/gcc/testsuite/g++.dg/warn/Wdangling-reference13.C
new file mode 100644
index 00000000000..bc09fbae22b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference13.C
@@ -0,0 +1,23 @@
+// PR c++/109774
+// { dg-do compile }
+// { dg-options "-Wdangling-reference" }
+
+int y;
+
+template<typename T>
+int& get(const char& )
+{
+ return y;
+}
+
+int& get2(const char&)
+{
+ return y;
+}
+
+int stuff(void)
+{
+ const int &h = get<void>(0); // { dg-bogus "dangling reference" }
+ const int &k = get2(0); // { dg-bogus "dangling reference" }
+ return h+k;
+}
base-commit: 94a311abf783de754f0f1b2d4c1f00a9788e795b
--
2.40.1
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] c++: -Wdangling-reference not suppressed in template [PR109774]
2023-05-16 19:13 [PATCH] c++: -Wdangling-reference not suppressed in template [PR109774] Marek Polacek
@ 2023-05-16 19:35 ` Jason Merrill
0 siblings, 0 replies; 2+ messages in thread
From: Jason Merrill @ 2023-05-16 19:35 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 5/16/23 15:13, Marek Polacek wrote:
> In check_return_expr, we suppress the -Wdangling-reference warning when
> we're sure it would be a false positive. It wasn't working in a
> template, though, because the suppress_warning call was never reached.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk and 13.2?
OK.
> PR c++/109774
>
> gcc/cp/ChangeLog:
>
> * typeck.cc (check_return_expr): In a template, return only after
> suppressing -Wdangling-reference.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/Wdangling-reference13.C: New test.
> ---
> gcc/cp/typeck.cc | 6 ++---
> .../g++.dg/warn/Wdangling-reference13.C | 23 +++++++++++++++++++
> 2 files changed, 26 insertions(+), 3 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/warn/Wdangling-reference13.C
>
> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
> index 53ac925a092..c225c4e2423 100644
> --- a/gcc/cp/typeck.cc
> +++ b/gcc/cp/typeck.cc
> @@ -11236,9 +11236,6 @@ check_return_expr (tree retval, bool *no_warning)
> build_zero_cst (TREE_TYPE (retval)));
> }
>
> - if (processing_template_decl)
> - return saved_retval;
> -
> /* A naive attempt to reduce the number of -Wdangling-reference false
> positives: if we know that this function can return a variable with
> static storage duration rather than one of its parameters, suppress
> @@ -11250,6 +11247,9 @@ check_return_expr (tree retval, bool *no_warning)
> && TREE_STATIC (bare_retval))
> suppress_warning (current_function_decl, OPT_Wdangling_reference);
>
> + if (processing_template_decl)
> + return saved_retval;
> +
> /* Actually copy the value returned into the appropriate location. */
> if (retval && retval != result)
> {
> diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference13.C b/gcc/testsuite/g++.dg/warn/Wdangling-reference13.C
> new file mode 100644
> index 00000000000..bc09fbae22b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference13.C
> @@ -0,0 +1,23 @@
> +// PR c++/109774
> +// { dg-do compile }
> +// { dg-options "-Wdangling-reference" }
> +
> +int y;
> +
> +template<typename T>
> +int& get(const char& )
> +{
> + return y;
> +}
> +
> +int& get2(const char&)
> +{
> + return y;
> +}
> +
> +int stuff(void)
> +{
> + const int &h = get<void>(0); // { dg-bogus "dangling reference" }
> + const int &k = get2(0); // { dg-bogus "dangling reference" }
> + return h+k;
> +}
>
> base-commit: 94a311abf783de754f0f1b2d4c1f00a9788e795b
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