We have had to work around a compiler optimization bug in XCode. It appears to be caused by versions of XCode starting sometime in Fall 2017. This also coincided with switching to OCC 7.2.0. In one instance adding [clang::optnone] to gp_Trsf::SetTransformation() fixed the problem. Some elements of the matrix were being incorrectly zeroed out. We have found other instances so we have had to turn optimizations down to O1 and rebuild the OCC libs. Has anyone else run into this?
XCode Compiler Optimization Bug