On Tue, Feb 05, 2019 at 01:24:15PM -0500, Jason Merrill wrote:
> On 2/5/19 11:31 AM, Jakub Jelinek wrote:
> > On Tue, Feb 05, 2019 at 11:24:14AM -0500, Jason Merrill wrote:
> > > Yes, thanks, mark_rvalue_use is definitely wrong here. But
> > > mark_lvalue_use
> > > might be wrong as well; we don't know here how the expression is used by
> > > the
> > > inner conversions for the user-defined conversion. Can we remove the call
> > > entirely? It doesn't seem to break any Wunused* tests.
> >
> > It was added in r159096 for -Wunused-but-set*. It is surely possible it is
> > now covered by other mark_*_use calls. Or could we call there just
> > mark_exp_read instead?
>
> That would be fine too.
So how about this if it passes testing?
Bootstrapped/regtested running on x86_64-linux, ok for trunk/8?
2019-02-05 Marek Polacek <pola...@redhat.com>
PR c++/89158 - by-value capture of constexpr variable broken.
* call.c (convert_like_real) <case ck_user>: Call mark_exp_read
instead of mark_rvalue_use.
* g++.dg/cpp0x/lambda/lambda-89158.C: New test.
diff --git gcc/cp/call.c gcc/cp/call.c
index c74d1b4ebdf..020a095dade 100644
--- gcc/cp/call.c
+++ gcc/cp/call.c
@@ -7006,7 +7006,9 @@ convert_like_real (conversion *convs, tree expr, tree fn,
int argnum,
return expr;
}
- expr = mark_rvalue_use (expr);
+ /* Calling mark_rvalue_use could turn a decl into a constant, breaking
+ e.g. the need_temporary_p assumption in the ICS. */
+ mark_exp_read (expr);
/* Pass LOOKUP_NO_CONVERSION so rvalue/base handling knows not to allow
any more UDCs. */
diff --git gcc/testsuite/g++.dg/cpp0x/lambda/lambda-89158.C
gcc/testsuite/g++.dg/cpp0x/lambda/lambda-89158.C
new file mode 100644
index 00000000000..15f15b46875
--- /dev/null
+++ gcc/testsuite/g++.dg/cpp0x/lambda/lambda-89158.C
@@ -0,0 +1,11 @@
+// PR c++/89158
+// { dg-do compile { target c++11 } }
+
+struct T { T(const int&); };
+void Func(T);
+
+void test()
+{
+ constexpr int Val = 42;
+ [Val]() { Func(Val); };
+}
