Ticket #117 (defect)

Build from latest SVN fails on Cygwin (gcc 3.4.4) and MinGW/MSYS (gcc 3.4.5) because

gr_math.cc: In function `int gr_isnan(double)':
gr_math.cc:66: error: `isnan' was not declared in this scope

In these versions of g++ isnan is defined as a macro in <math.h> unless <cmath> is included, in which case std::isnan() is defined instead. The configure script (config/lf_cxx.m4) uses <math.h> and thus doesn't find std::isnan(), but (since revision 4108) gr_math.h includes <gr_complex.h> which indirectly includes <cmath>. So std::isnan() is defined, but CXX_HAS_STD_ISNAN is not defined, and isnan (as a macro) is not defined.

It seems that the test for isnan performed in lf_cxx.m4 should match the usage of isnan in the code---either both should include <cmath> or neither should include <cmath>.

At present (since revision 4108), all code in GNU Radio that references isnan includes <cmath>; attached is a patch for lf_cxx.m4 that works in this case.