On Jan 1, 2012, at 4:30 PM, Steve M. Robbins wrote:
Hello,
Boost Developers: I recently did rebuilds of all Debian packages that use Boost with Boost 1.48 and this is one of the casualties of the upgrade (from 1.46.1).
On Sat, Dec 31, 2011 at 12:02:37PM +0100, Zack Weinberg wrote:
On Fri, Dec 30, 2011 at 9:53 PM, Steve M. Robbins <smr@debian.org> wrote:
This package failed to build using the newest Boost version 1.48: ... /usr/include/boost/math/special_functions/detail/lgamma_small.hpp: In function 'T boost::math::detail::lgamma_small_imp(T, T, T, const mpl_::int_<0>&, const Policy&, const L&)': ... /usr/include/boost/math/special_functions/detail/lgamma_small.hpp:483:38: error: expected primary-expression before 'do'
I'm not in a position to verify this for myself for another week, but I have a horrible feeling I know what's wrong: Monotone defines several one-character macros for its own use, and L() is one of them. It looks like Boost is using L() for its own purposes and expecting it not to be a macro.
Zack, you are absolutely right. The lgamma_small header has a templated class method using "L" as one of the templates:
template <class T, class Policy, class L> T lgamma_small_imp(T z, T zm1, T zm2, const mpl::int_<0>&, const Policy& pol, const L&)
The compile error at line 483 is at a call to L():
result = log(gamma_imp(z, pol, L()));
I'd argue that Boost headers should take care to defend themselves from the possibility of such macros, but fixing that in Boost might be an enormous amount of work, and in any case, 1.48 is already out there.
How, though? #undef L That would break client code.
Boost.Math developers: What is the right thing to do here? More descriptive class template parameters?
This is a hard problem - because pretty much whatever identifier gets chosen, you have a chance that some program/library/package somewhere has defined it in a macro. Several years ago, I worked with a guy who was passionately anti-C++. He said, "Look - it's all crap. if I add '#include <vector>' to my source file, all of a sudden I get all these compile errors! What kind of idiot writes this stuff?" Finally, I got tired of his complaining, and looked at the problems that he was having. Buried in one of his header files was '#define T true' ;-) -- Marshall Marshall Clow Idio Software <mailto:mclow.lists@gmail.com> A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki