Re: [PATCH] Fix constexpr evaluation of comparisons involving pointer-to-members

[Patrick Palka <patrick at parcs dot ath dot cx>]

On Sun, Jan 10, 2016 at 10:19 PM, Patrick Palka <patrick@parcs.ath.cx> wrote:
> On Mon, Dec 21, 2015 at 6:07 PM, Patrick Palka <patrick@parcs.ath.cx> wrote:
>> We are currently failing to fold equality comparisons involving
>> PTRMEM_CSTs since (I think) r229018 thus making this a GCC 6 regression.
>> This regression shows up in the boost testsuite.
>>
>> Fixed in a straightforward way.  OK to commit after bootstrap + regtest?
>>
>> gcc/cp/ChangeLog:
>>
>>         * constexpr.c (cxx_eval_binary_expression): Expand
>>         the PTRMEM_CST operands of an equality comparison.
>>
>> gcc/testsuite/ChangeLog:
>>
>>         * g++.dg/cpp0x/constexpr-ptrmem5.C: New test.
>> ---
>>  gcc/cp/constexpr.c                             |  9 +++++++++
>>  gcc/testsuite/g++.dg/cpp0x/constexpr-ptrmem5.C | 14 ++++++++++++++
>>  2 files changed, 23 insertions(+)
>>  create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-ptrmem5.C
>>
>> diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
>> index 208f43b..1ad87aa 100644
>> --- a/gcc/cp/constexpr.c
>> +++ b/gcc/cp/constexpr.c
>> @@ -1630,6 +1630,15 @@ cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t,
>>    location_t loc = EXPR_LOCATION (t);
>>    enum tree_code code = TREE_CODE (t);
>>    tree type = TREE_TYPE (t);
>> +
>> +  if (code == EQ_EXPR || code == NE_EXPR)
>> +    {
>> +      if (TREE_CODE (lhs) == PTRMEM_CST && CONSTANT_CLASS_P (rhs))
>> +       lhs = cplus_expand_constant (lhs);
>> +      if (TREE_CODE (rhs) == PTRMEM_CST && CONSTANT_CLASS_P (lhs))
>> +       rhs = cplus_expand_constant (rhs);
>> +    }
>> +
>>    r = fold_binary_loc (loc, code, type, lhs, rhs);
>>    if (r == NULL_TREE)
>>      {
>> diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ptrmem5.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ptrmem5.C
>> new file mode 100644
>> index 0000000..e28c917
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ptrmem5.C
>> @@ -0,0 +1,14 @@
>> +// { dg-do compile { target c++11 } }
>> +
>> +#define SA(x) static_assert ((x), #x)
>> +
>> +struct X { int a, b; };
>> +
>> +void
>> +foo ()
>> +{
>> +  SA (&X::a);
>> +  SA (&X::a == &X::a);
>> +  SA (&X::a != &X::b);
>> +  SA ((!&X::b) == 0);
>> +}
>> --
>> 2.7.0.rc0.50.g1470d8f.dirty
>>
>
> Ping.

Ping.