Hi!
As written in the PR, location wrappers are stripped by
cxx_eval_constant_expression as the first thing it does after dealing with
jump_target. The problem is that when this function is called on a
CONSTRUCTOR, is TREE_CONSTANT and reduced_constant_expression_p (which
allows location wrappers around constants), we don't recurse on the
CONSTRUCTOR elements and so nothing strips them away. Then when
cxx_eval_component_reference or bit_field_ref we actually can run into those
location wrappers and the callers assume they don't appear anymore.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
I admit I'm not 100% sure about the second case which will call the function
to do the stripping for all the elts until the one found. The alternative
would be:
tree bitpos = bit_position (field);
if (bitpos == start && DECL_SIZE (field) == TREE_OPERAND (t, 1))
- return value;
+ {
+ STRIP_ANY_LOCATION_WRAPPER (value);
+ return value;
+ }
if (TREE_CODE (TREE_TYPE (field)) == INTEGER_TYPE
- && TREE_CODE (value) == INTEGER_CST
&& tree_fits_shwi_p (bitpos)
&& tree_fits_shwi_p (DECL_SIZE (field)))
{
HOST_WIDE_INT bit = tree_to_shwi (bitpos);
HOST_WIDE_INT sz = tree_to_shwi (DECL_SIZE (field));
HOST_WIDE_INT shift;
if (bit >= istart && bit + sz <= istart + isize)
{
+ STRIP_ANY_LOCATION_WRAPPER (value);
+ if (TREE_CODE (value) != INTEGER_CST)
+ continue;
but then we'd do those tree_fits_shwi_p/tree_to_shwi. Guess
a micro-optimization without a clear winner.
2019-10-17 Jakub Jelinek <ja...@redhat.com>
PR c++/92015
* constexpr.c (cxx_eval_component_reference, cxx_eval_bit_field_ref):
Use STRIP_ANY_LOCATION_WRAPPER on CONSTRUCTOR elts.
* g++.dg/cpp0x/constexpr-92015.C: New test.
--- gcc/cp/constexpr.c.jj 2019-10-16 09:30:57.300112739 +0200
+++ gcc/cp/constexpr.c 2019-10-16 17:06:03.943539476 +0200
@@ -2887,7 +2887,10 @@ cxx_eval_component_reference (const cons
: field == part)
{
if (value)
- return value;
+ {
+ STRIP_ANY_LOCATION_WRAPPER (value);
+ return value;
+ }
else
/* We're in the middle of initializing it. */
break;
@@ -2977,6 +2980,7 @@ cxx_eval_bit_field_ref (const constexpr_
FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (whole), i, field, value)
{
tree bitpos = bit_position (field);
+ STRIP_ANY_LOCATION_WRAPPER (value);
if (bitpos == start && DECL_SIZE (field) == TREE_OPERAND (t, 1))
return value;
if (TREE_CODE (TREE_TYPE (field)) == INTEGER_TYPE
--- gcc/testsuite/g++.dg/cpp0x/constexpr-92015.C.jj 2019-10-16
17:16:44.204871319 +0200
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-92015.C 2019-10-16
17:14:14.773127884 +0200
@@ -0,0 +1,7 @@
+// PR c++/92015
+// { dg-do compile { target c++11 } }
+
+struct S1 { char c[6] {'h', 'e', 'l', 'l', 'o', 0}; };
+struct S2 { char c[6] = "hello"; };
+static_assert (S1{}.c[0] == 'h', "");
+static_assert (S2{}.c[0] == 'h', "");
Jakub
