When compiling the POCO Foundation library with POCO_NO_FPENVIRONMENT set in Config.h (not via configure), then FPEnvironment_C99.cpp is still pulled in. The cause seems to be that in FPEnvironment.cpp the flag POCO_NO_FPENVIRONMENT is not available.

While Poco/Platform.h is included in

, this should be also the case for Poco/Config.h in order to have the flag POCO_NO_FPENVIRONMENT available.