[R] Cannot call R's ISNAN() from a C code in >1.7 versions.

[Paul Y. Peng]

Dear R users,

Have you experienced any difficulty in calling R's ISNAN() from a C
code? I have C codes including ISNAN() calls and they worked well until
I upgraded my R from 1.7 to later versions. When I tried to compile the
codes in the version 1.8 and 1.9, I got error messages like this:

   test.obj : error LNK2001: unresolved external symbol _isnan
   .\testR.dll : fatal error LNK1120: 1 unresolved externals
   NMAKE : fatal error U1077: 'link.exe' : return code '0x460'
   Stop.

I checked "Writing R Extensions" and did not find any changes in the API
entry point for ISNAN in the later versions. Could any one enlighten me
on why _isnan cannot be resolved? The compiler I used is MSVC++ 6.0 and
the platform is WinXP. Many thanks.

Paul.