I steered Jakub wrong on the desired behavior for temp-extend1.C in the
context of bug 92831; it doesn't make sense to try to extend the lifetime of
a temporary that we've already materialized to evaluate the test. So this
patch munges the stabilized expression so that it won't be subject to
lifetime extension.
Tested x86_64-pc-linux-gnu, applying to trunk.
* call.c (prevent_lifetime_extension): New.
(build_conditional_expr_1): Use it.
---
gcc/cp/call.c | 24 +++++++++++++++++++++++-
gcc/testsuite/g++.dg/ext/temp-extend1.C | 2 +-
2 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 9a22398e794..32ccfc973e4 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -217,6 +217,7 @@ static conversion *merge_conversion_sequences (conversion
*, conversion *);
static tree build_temp (tree, tree, int, diagnostic_t *, tsubst_flags_t);
static conversion *build_identity_conv (tree, tree);
static inline bool conv_binds_to_array_of_unknown_bound (conversion *);
+static tree prevent_lifetime_extension (tree);
/* Returns nonzero iff the destructor name specified in NAME matches BASETYPE.
NAME can take many forms... */
@@ -5078,7 +5079,10 @@ build_conditional_expr_1 (const op_location_t &loc,
/* Make sure that lvalues remain lvalues. See g++.oliva/ext1.C. */
if (glvalue_p (arg1))
- arg2 = arg1 = cp_stabilize_reference (arg1);
+ {
+ arg2 = arg1 = cp_stabilize_reference (arg1);
+ arg2 = arg1 = prevent_lifetime_extension (arg1);
+ }
else
arg2 = arg1 = cp_save_expr (arg1);
}
@@ -12168,6 +12172,24 @@ initialize_reference (tree type, tree expr,
return expr;
}
+/* If *P is an xvalue expression, prevent temporary lifetime extension if it
+ gets used to initialize a reference. */
+
+static tree
+prevent_lifetime_extension (tree t)
+{
+ tree *p = &t;
+ while (TREE_CODE (*p) == COMPOUND_EXPR)
+ p = &TREE_OPERAND (*p, 1);
+ while (handled_component_p (*p))
+ p = &TREE_OPERAND (*p, 0);
+ /* Change a TARGET_EXPR from prvalue to xvalue. */
+ if (TREE_CODE (*p) == TARGET_EXPR)
+ *p = build2 (COMPOUND_EXPR, TREE_TYPE (*p), *p,
+ move (TARGET_EXPR_SLOT (*p)));
+ return t;
+}
+
/* Subroutine of extend_ref_init_temps. Possibly extend one initializer,
which is bound either to a reference or a std::initializer_list. */
diff --git a/gcc/testsuite/g++.dg/ext/temp-extend1.C
b/gcc/testsuite/g++.dg/ext/temp-extend1.C
index 7df9ca51681..aaef115494c 100644
--- a/gcc/testsuite/g++.dg/ext/temp-extend1.C
+++ b/gcc/testsuite/g++.dg/ext/temp-extend1.C
@@ -21,7 +21,7 @@ baz (int i)
{
const bool&& a = id<S[3]>{false, true, false}[i].s
? : id<S[4]>{true, false, true, false}[i].s;
- if (S::c != (i ? 3 : 4))
+ if (S::c != (i ? 0 : 4))
__builtin_abort ();
}
base-commit: bc071d3a951a98284a3f46043afd44c03c123376
--
2.18.1
