Hi Trevis, > Any suggestions for more speedily tracking this problem down? I use the output from GCC. For example... : cat test.cpp #define FOO 9 #define FOO 8 : g++ -DFOO -c test.cpp test.cpp:1:1: warning: "FOO" redefined <command line>:1:1: warning: this is the location of the previous definition test.cpp:2:1: warning: "FOO" redefined test.cpp:1:1: warning: this is the location of the previous definition I can see that line 1 of test.cpp redefines FOO, which was previously specified on the command line. Also, line 2 of test.cpp redefines FOO, which was #define'd (or really, re#define'd) previously on line 1. HTH, --Eljay