The program options library now fails a single test on Darwin, with this output: ../libs/program_options/test/parsers_test.cpp(205): fatal error in "call_test_main": test p.options.size() == 1 failed *** 1 failure detected in test case "call_test_main" The code in question is: putenv("PO_TEST_FOO=1"); parsed_options p = parse_environment(desc, "PO_TEST_"); BOOST_REQUIRE(p.options.size() == 1); So, it seems that after "putenv", the string is is not available in the 'environ' variable. The variable is declared like this: #if defined(__APPLE__) && defined(__DYNAMIC__) #include <crt_externs.h> static char** environ = *_NSGetEnviron(); #else extern char** environ; #endif The Darwin-specific conditinal was sent by Michael LaSpina, so I don't know what it really does, and so don't know why the test fails. I'd appreciate any suggestions. Thanks in advance, Volodya