Re: [boost] [mpl] int_<INT_MIN> fails to compile under gcc 4.6

Subject: Re: [boost] [mpl] int_<INT_MIN> fails to compile under gcc 4.6
From: Philipp Reh (sefi_at_[hidden])
Date: 2011-03-06 07:24:03

Stirling Westrup wrote:

> On Sun, Mar 6, 2011 at 5:50 AM, Philipp Reh <sefi_at_[hidden]> wrote:
>> Stirling Westrup wrote:
>>
>>> I'm not actually sure if this is a gcc regression, or a bug in mpl,
>>> but the following code, which compiles under gcc 4.5, doesn't do so
>>> under gcc 4.6:
>>>
>>> #include <climits>
>>> #include <boost/mpl/int.hpp>
>>> typedef boost::mpl::int_<INT_MIN> Foo;
>>> Foo f;
>>>
>>>
>>> It produces the errors:
>>>
>>> /usr/local/include/boost/mpl/aux_/integral_wrapper.hpp: In
>>> instantiation of ‘mpl_::int_<-0x00000000080000000>’:
>>> test_test.cpp:8:27:   instantiated from here
>>> /usr/local/include/boost/mpl/aux_/integral_wrapper.hpp:73:96: error:
>>> ‘2147483647’ is not a valid template argument for type ‘int’ because
>>> it is a non-constant expression
>>> /usr/local/include/boost/mpl/aux_/integral_wrapper.hpp:73:96: error:
>>> overflow in constant expression [-fpermissive]
>>>
>>>
>>> I've already created a trak ticket for this (#5268), but was wondering
>>> if anyone had any insights as to its cause and/or any workarounds. My
>>> guess is that its related to gcc rewriting parts of its constant
>>> folding code to support constexpr.
>>>
>>>
>>>
>>>
>>>
>>
>> I can confirm that. INT_MIN isn't the only problem, it fails for a lot of
>> other values as well.
>> Can you please raise this issue on the gcc bugtracker because the release
>> is very close.
>>
> 
> Okay, I have done so. Its bug #48003 on the GCC bugtracker.
> 
> 
> 

Thanks. After looking further into this I realized that mpl tries to 
calculate INT_MIN-1 which, of course, is undefined. But I'm still not sure 
if this is a gcc bug or not because the typedef isn't used and I don't know 
if gcc should evaluate this.