Hi,
In PR c++/44859, it is noted that the following code does not emit a
"returning reference to temporary" warning:
struct Base2 { int m_foo; };
struct Derived2 : public Base2 {};
const Base2& f8() { return Derived2(); } // <-- here
The source of the problem seems to be that
maybe_warn_about_returning_address_of_local() does not look through
COMPONENT_REFs in a function's return value if the function's return
type is a REFERENCE_TYPE. This patch simply changes the just mentioned
function to look through COMPONENT_REFs (and ARRAY_REFs)
unconditionally.
This change was successfully bootstrapped and regtested against
x86_64-unknown-linux-gnu.
2014-03-31 Patrick Palka patr...@parcs.ath.cx
PR c++/44859
* typeck.c (maybe_warn_about_returning_address_of_local): Unwrap
COMPONENT_REFs and ARRAY_REFs sooner.
---
gcc/cp/typeck.c | 8 ++++----
gcc/testsuite/g++.dg/warn/Wreturn-local-addr-2.C | 11 +++++++++++
2 files changed, 15 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wreturn-local-addr-2.C
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 559f19b5..9a80727 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -8283,6 +8283,10 @@ maybe_warn_about_returning_address_of_local (tree retval)
return;
whats_returned = TREE_OPERAND (whats_returned, 0);
+ while (TREE_CODE (whats_returned) == COMPONENT_REF
+ || TREE_CODE (whats_returned) == ARRAY_REF)
+ whats_returned = TREE_OPERAND (whats_returned, 0);
+
if (TREE_CODE (valtype) == REFERENCE_TYPE)
{
if (TREE_CODE (whats_returned) == AGGR_INIT_EXPR
@@ -8300,10 +8304,6 @@ maybe_warn_about_returning_address_of_local (tree retval)
}
}
- while (TREE_CODE (whats_returned) == COMPONENT_REF
- || TREE_CODE (whats_returned) == ARRAY_REF)
- whats_returned = TREE_OPERAND (whats_returned, 0);
-
if (DECL_P (whats_returned)
&& DECL_NAME (whats_returned)
&& DECL_FUNCTION_SCOPE_P (whats_returned)
diff --git a/gcc/testsuite/g++.dg/warn/Wreturn-local-addr-2.C
b/gcc/testsuite/g++.dg/warn/Wreturn-local-addr-2.C
new file mode 100644
index 0000000..c483601
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wreturn-local-addr-2.C
@@ -0,0 +1,11 @@
+// PR c++/44859
+
+struct Base2 { int m_foo; };
+struct Derived2 : public Base2 {};
+
+const Base2& f8() { return Derived2(); } // { dg-warning "reference to
temporary" }
+
+struct foo { };
+struct bar { foo base; };
+
+const foo& f9() { return bar().base; } // { dg-warning "reference to
temporary" }
--
1.9.1
