Hello I am using the trunk release of boost, and started having problems with multiple definitions of symbols during linking (see example linker output below). I can cure the problem by removing the change to tools\build\v2\build\generators.jam introduced in revision 49800. It only seems to occur if the following headers: #include <boost/test/floating_point_comparison.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/bind.hpp> are included in precompiled headers which are included in cpp files that are created by the antlr parser generator. It occurs on a compilation with darwin, but not msvc. It is unclear whether the generator.jam change has identified a waekness in the boost libraries, or there is a problem with the revision 49800 change that only surfaces in obscure circumstances, or the change has highlighted a problem in my code. It can be fixed by removing the includes from the precompiled header. I feel this should not be necessary As a boost newbie it is unclear whether I should I change my code or raise a bug report. I would be grateful for suggestions. Nigel Example linker failures. /usr/libexec/gcc/i686-apple-darwin8/4.0.1/ld: multiple definitions of symbol boost::test_tools::(anonymous namespace)::check_is_close /Volumes/RAID1/xraid/data/bifa/Dev/Projects/Bio/bin/Bio/darwin-4.0.1/release/link-static/libbio.a(BiobaseLexer.o) definition of boost::test_tools::(anonymous namespace)::check_is_close in section (__DATA,__const) /Volumes/RAID1/xraid/data/bifa/Dev/Projects/Bio/bin/Bio/darwin-4.0.1/release/link-static/libbio.a(ArrayLexer.o) definition of boost::test_tools::(anonymous namespace)::check_is_close in section (__DATA,__const)