Tested x86_64-pc-linux-gnu. Marek, thoughts?
-- 8< --
The -Wdangling-reference diagnostic talks about the full-expression, but
prints one call, while the full-expression in a declaration is the entire
initialization. It seems more useful to point out the temporary that the
compiler thinks we might be getting a dangling reference to.
gcc/cp/ChangeLog:
* call.cc (do_warn_dangling_reference): Return temporary
instead of the call it's passed to.
(maybe_warn_dangling_reference): Adjust diagnostic.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wdangling-reference1.C: Adjust diagnostic.
---
gcc/cp/call.cc | 23 +++++++++----------
.../g++.dg/warn/Wdangling-reference1.C | 2 +-
2 files changed, 12 insertions(+), 13 deletions(-)
diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 1ecf3aac705..3f753e2d2f9 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -14253,19 +14253,18 @@ reference_like_class_p (tree ctype)
return false;
}
-/* Helper for maybe_warn_dangling_reference to find a problematic CALL_EXPR
- that initializes the LHS (and at least one of its arguments represents
- a temporary, as outlined in maybe_warn_dangling_reference), or NULL_TREE
+/* Helper for maybe_warn_dangling_reference to find a problematic temporary
+ in EXPR (as outlined in maybe_warn_dangling_reference), or NULL_TREE
if none found. For instance:
- const S& s = S().self(); // S::self (&TARGET_EXPR <...>)
- const int& r = (42, f(1)); // f(1)
- const int& t = b ? f(1) : f(2); // f(1)
- const int& u = b ? f(1) : f(g); // f(1)
- const int& v = b ? f(g) : f(2); // f(2)
+ const S& s = S().self(); // S()
+ const int& r = (42, f(1)); // temporary for passing 1 to f
+ const int& t = b ? f(1) : f(2); // temporary for 1
+ const int& u = b ? f(1) : f(g); // temporary for 1
+ const int& v = b ? f(g) : f(2); // temporary for 2
const int& w = b ? f(g) : f(g); // NULL_TREE
const int& y = (f(1), 42); // NULL_TREE
- const int& z = f(f(1)); // f(f(1))
+ const int& z = f(f(1)); // temporary for 1
EXPR is the initializer. If ARG_P is true, we're processing an argument
to a function; the point is to distinguish between, for example,
@@ -14365,7 +14364,7 @@ do_warn_dangling_reference (tree expr, bool arg_p)
&& !reference_related_p (TREE_TYPE (rettype),
TREE_TYPE (arg)))
continue;
- return expr;
+ return arg;
}
/* Don't warn about member functions like:
std::any a(...);
@@ -14438,8 +14437,8 @@ maybe_warn_dangling_reference (const_tree decl, tree
init)
auto_diagnostic_group d;
if (warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wdangling_reference,
"possibly dangling reference to a temporary"))
- inform (EXPR_LOCATION (call), "the temporary was destroyed at "
- "the end of the full expression %qE", call);
+ inform (EXPR_LOCATION (call), "%qT temporary created here",
+ TREE_TYPE (call));
}
}
diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference1.C
b/gcc/testsuite/g++.dg/warn/Wdangling-reference1.C
index a184317dd5c..5e60a415836 100644
--- a/gcc/testsuite/g++.dg/warn/Wdangling-reference1.C
+++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference1.C
@@ -117,7 +117,7 @@ const B& b10 = lox (H{}); // { dg-warning "dangling
reference" }
struct S {
const int &r; // { dg-warning "dangling reference" }
- S() : r(f(10)) { } // { dg-message "destroyed" }
+ S() : r(f(10)) { } // { dg-message "created" }
};
// From cppreference.
--
2.46.0
