There is a known bug with MSVC71 where if you use __LINE__ too much (not sure what the limits are or under what circumstances though), you get a "Fatal Error: Out of Keys" or something similar. Instead of this, for generating unique variable names etc I have seen the __COUNTER__ macro used instead, which provides similar functionality, but doesn't seem to suffer from this issue. Yours, Stewart -----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users-bounces@lists.boost.org]On Behalf Of Wu Yinghui, Freddie Sent: 08 March 2006 09:00 To: boost-users@lists.boost.org Subject: [Boost-users] Boost.Preprocessor with __LINE__ in MSVC71 Hi all, I'm observing an interesting problem on MSVC71 regarding the use of __LINE__ with Boost.Preprocessor. The code looks like this ==== snip ==== #include <boost/preprocessor/cat.hpp> #define UNIQUE_ID BOOST_PP_CAT(id, __LINE__) #define UNIQUE_ID2 BOOST_PP_CAT(id, _MSC_VER) int main() { int UNIQUE_ID2 = 321; int UNIQUE_ID = 123; bool UNIQUE_ID = false; } ==== snip ==== The compiler works fine with UNIQUE_ID2, but not UNIQUE_ID. The only different in them is only the use of __LINE__ instead of _MSC_VER. Does anyone on the list has more insight on this issue? Or, what're the common ways to generate an unique identifier automatically within certain scope? Cheers, Freddie -- Wu Yinghui, Freddie Research & Development Software Engineer Volume Interactions Pte Ltd 1 Kim Seng Promenade, #12-01 Great World City East Tower Singapore 237994 Tel: +65 62226962 (Ext 216) Fax: +65 62226215 Email: yhwu@volumeinteractions.com URL: http://www.volumeinteractions.com Important: This message is intended for the recipient(s) addressed above. It contains privileged and confidential information. If you are not the intended recipient, please notify the sender immediately by replying to this message and then delete it from your system. You must not read, copy, use, or disseminate this communication in any form. Thank you. ________________________________________________________________________ This e-mail has been scanned for viruses by MessageLabs. ________________________________________________________________________ This e-mail has been scanned for viruses by MessageLabs.