On Fri, Feb 16, 2018 at 08:52:10AM -0500, Jason Merrill wrote:
> On Fri, Feb 16, 2018 at 3:28 AM, Jakub Jelinek <ja...@redhat.com> wrote:
> > pop_stmt_list, if there is just a single stmt inside statement expression
> > moves the stmt out of the STATEMENT_LIST (and I think cp_fold does too).
> > We only initialize jump_target to non-NULL in cxx_eval_statement_list
> > or for calls, so before we have a chance to diagnose the error of using
> > an expression with void type, we ICE trying to dereference NULL jump_target.
> >
> > This can't happen with BREAK_STMT nor CONTINUE_STMT, because they are not
> > potential constant expressions, and I think can only happen when ctx->quiet
> > is true, otherwise it should have been diagnosed already before.
> > If a RETURN_EXPR (or in theory break/continue) appears in a (potential)
> > constant
> > expression we want to evaluate, not doing anything with jump_target if we
> > aren't inside a statement list makes sense to me, there is no following
> > statement to bypass.
>
> I think we should also set *non_constant_p.
Just like this? Tested so far just on the testcase, but given that we'd ICE
on the *jump_target before, it can't really regress anything else (though of
course I'll bootstrap/regtest it normally).
2018-02-16 Marek Polacek <pola...@redhat.com>
Jakub Jelinek <ja...@redhat.com>
PR c++/84192
* constexpr.c (cxx_eval_constant_expression) <case RETURN_EXPR>: Don't
set *jump_target to anything if jump_target is NULL.
* g++.dg/cpp1y/constexpr-84192.C: New test.
--- gcc/cp/constexpr.c.jj 2018-02-12 19:17:37.937216029 +0100
+++ gcc/cp/constexpr.c 2018-02-15 16:10:56.630572360 +0100
@@ -4254,7 +4254,16 @@ cxx_eval_constant_expression (const cons
r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0),
lval,
non_constant_p, overflow_p);
- *jump_target = t;
+ if (jump_target)
+ *jump_target = t;
+ else
+ {
+ /* Can happen with ({ return true; }) && false; passed to
+ maybe_constant_value. There is nothing to jump over in this
+ case, and the bug will be diagnosed later. */
+ gcc_assert (ctx->quiet);
+ *non_constant_p = true;
+ }
break;
case SAVE_EXPR:
--- gcc/testsuite/g++.dg/cpp1y/constexpr-84192.C.jj 2018-02-15
16:00:58.242588914 +0100
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-84192.C 2018-02-15
16:01:30.219585291 +0100
@@ -0,0 +1,41 @@
+// PR c++/84192
+// { dg-do compile { target c++14 } }
+// { dg-options "" }
+
+bool
+f1 ()
+{
+ return ({ return true; }) && false; // { dg-error "could not convert" }
+}
+
+void
+f2 ()
+{
+ for (;;)
+ constexpr bool b = ({ break; false; }) && false; // { dg-error
"statement is not a constant expression" }
+}
+
+constexpr bool
+f3 (int n)
+{
+ bool b = false;
+ for (int i = 0; i < n; i++)
+ b = ({ break; }); // { dg-error "void value not ignored as it ought to
be" }
+ return b;
+}
+
+constexpr bool b = f3 (4);
+
+bool
+f4 ()
+{
+ constexpr bool b = ({ return true; }) && false; // { dg-error "could
not convert" }
+ return false;
+}
+
+constexpr bool
+f5 (int x)
+{
+ constexpr bool b = ({ switch (x) case 0: true; }) && false; // { dg-error
"could not convert" }
+ return false;
+}
Jakub
