Joaquín Mª López Muñoz writes:
I've been investigating the problem a little further, and the final results are these:
Seems like handling of MPL lambda expressions is difficult with GCC 2.95. The following snippet:
typedef transform1< vector<char,int,double>, XXX
::type t1;
has several outcomes depending on XXX 1. identity<_1>: OK 2. mpl::sizeof<_1>: complains about an expression not being constant. However, code like this is embedded into Boost.Variant and seems to work fine (??) 3. boost::alignment_of<_1>: ICEs like I previously described. This is the error Boost.Variant is currently running into.
My skills are too limited to be able to find a reason for this behavior, so I hope people smarter than me can do something with this.
In case this problem is finally *not* taken care of, I've managed to workaround the regressions in Boost.Variant with a patch to be applied to boost/variant/variant.hpp (attached). Basically, the patch avoids the use of boost::aligment_of<_1> in favor of a more traditional metafunction class.
So, if someone is able to fix this problem by touching either MPL or type_traits, so much the better.
Joaquín, Thank you for investigating this! I'll dig a little further into it later tonight to see if we can fix it in MPL.
Otherwise, does anybody see a problem with me commiting the patch to Boost.Variant?
Nope, but let me try the above first. -- Aleksey Gurtovoy MetaCommunications Engineering