[Developers] does anybody understand __cplusplus

[John Sibert]

The __cplusplus macro used as follows in the threaded protoype version 
of the autodif library.
#if (__cplusplus > 199711L)
   #define __ADMBTHREAD__ __thread
#else
   #define __ADMBTHREAD__
#endif

I got curious about it since I always thought is should be 1. However, 
various  internet disinformation yields confusing "epertize" on the 
interpretation of of this macro. Here is one explanation.
>
> __cplusplus
>
>     This macro is defined when the C++ compiler is in use. You can use
>     __cplusplus to test whether a header is compiled by a C compiler
>     or a C++ compiler. This macro is similar to __STDC_VERSION__, in
>     that it expands to a version number. A fully conforming
>     implementation of the 1998 C++ standard will define this macro to
>     199711L. The GNU C++ compiler is not yet fully conforming, so it
>     uses 1 instead. It is hoped to complete the implementation of
>     standard C++ in the near future.
>
However larger values, indicating more recent and standard-conforming 
(?) versions of the compiler. These are apparently intend for arm 
devices? So __ADMBTHREAD__ is only defined for arm compilers?

I did a little experiment on a the new admb workstation (katsuo) and on 
my 4 year old laptop (kolea). Apparently gcc 4.4 is not up to standard. 
(I'm trying to install 4.7.2 on kolea, but that is a different tale of woe.)

tagest: tag movement estimation procedure; ADMB implementation.
   Source directory: /home/jsibert/movemod/25
   SVN revision number: 3009
   Compiler: Gnu C++4.7.2 on katsuo
   Architecture: 64 bits
   Operating system: linux-gnu
   Safe ADMB libraries, Version

starting time: Wed Dec 31 14:00:00 1969

line 1233, file linux-gnu/tagest.cpp, __cplusplus = 199711
line 1235, file linux-gnu/tagest.cpp, sysconf(_SC_NPROCESSORS_CONF) = 
12, sysconf(_SC_NPROCESSORS_ONLN) = 12


tagest: tag movement estimation procedure; ADMB implementation.
   Source directory: /home/jsibert/movemod/25
   SVN revision number: 3029M
   Compiler: Gnu C++4.4.3 on kolea
   Architecture: 64 bits
   Operating system: linux-gnu
   Safe ADMB libraries, Version

starting time: Wed Dec 31 14:00:00 1969

line 1236, file linux-gnu/tagest.cpp, __cplusplus = 1
line 1238, file linux-gnu/tagest.cpp, sysconf(_SC_NPROCESSORS_CONF) = 2, 
sysconf(_SC_NPROCESSORS_ONLN) = 2

Have a nice weekend,
John

-- 
John Sibert
Emeritus Researcher, SOEST
University of Hawaii at Manoa

Visit the ADMB project http://admb-project.org/