Hi!
The following valid testcase is rejected, because cxx_eval_binary_expression
is called on the SPACESHIP_EXPR with lval = true, as the address of the
spaceship needs to be passed to a method call.
After recursing on the operands and calling genericize_spaceship which turns
it into a TARGET_EXPR with initialization, we call cxx_eval_constant_expression
on it which succeeds, but then we fall through into code that will
VERIFY_CONSTANT (r) which FAILs because it is an address of a variable. Rather
than avoiding that for lval = true and SPACESHIP_EXPR, the patch just tail
calls cxx_eval_constant_expression - I believe that call should perform all
the needed verifications.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk (and
later for 10.3)?
2020-08-08 Jakub Jelinek <ja...@redhat.com>
PR c++/96497
* constexpr.c (cxx_eval_binary_expression): For SPACESHIP_EXPR, tail
call cxx_eval_constant_expression after genericize_spaceship to avoid
undesirable further VERIFY_CONSTANT.
* g++.dg/cpp2a/spaceship-constexpr3.C: New test.
--- gcc/cp/constexpr.c.jj 2020-08-06 11:35:12.997122440 +0200
+++ gcc/cp/constexpr.c 2020-08-07 13:30:28.732376843 +0200
@@ -3085,8 +3085,8 @@ cxx_eval_binary_expression (const conste
else if (code == SPACESHIP_EXPR)
{
r = genericize_spaceship (type, lhs, rhs);
- r = cxx_eval_constant_expression (ctx, r, lval, non_constant_p,
- overflow_p);
+ return cxx_eval_constant_expression (ctx, r, lval, non_constant_p,
+ overflow_p);
}
if (r == NULL_TREE)
--- gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C.jj 2020-08-07
13:37:34.883410112 +0200
+++ gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr3.C 2020-08-07
13:38:09.988918586 +0200
@@ -0,0 +1,7 @@
+// PR c++/96497
+// { dg-do compile { target c++20 } }
+
+#include <compare>
+
+static_assert(std::partial_ordering(std::strong_ordering::less) < 0);
+static_assert(std::partial_ordering(1 <=> 2) < 0);
Jakub
