This example fails to compile on Sequoia 15.4 with Xcode 16.3 and the command line tools installed; jacquesmenu@macstudio:C++Tests > cat pcount_test.cpp // clang++ -std=c++17 -o IntWrapperTest IntWrapperTest.cpp #include // std::string #include // std::cout #include // std::ostringstream int main1 (int argc, char* argv[]) { std::string theString = "Prière d'éviter"; std::cout << theString << ", size(): " << theString.size () << std::endl; std::stringstream oss; oss << theString << std::endl; std::cout << oss.str () << ", pcount(): " << oss.pcount () << std::endl; } //_______________________________________________________________________________ // position in output stream #include // std::ofstream int main () { std::ofstream outfile; outfile.open ("test.txt"); outfile.write ("This is an apple",16); long pos = outfile.tellp(); outfile.seekp (pos-7); outfile.write (" sam",4); outfile.close(); return 0; } jacquesmenu@macstudio:C++Tests > clang++ pcount_test.cpp pcount_test.cpp:3:10: fatal error: 'string' file not found 3 | #include // std::string | ^~~~~~~~ 1 error generated. The same occurs with iostrem if it is the first include mentioned. Compiling in Xcode itself does not this problem, though. This include is to be found here: jacquesmenu@macstudio:C++Tests > xcode-select -p /Applications/Xcode.app/Contents/Developer jacquesmenu@macstudio:C++Tests > ls -sal /Applications/Xcode.app/Contents/Developer/**/string | grep MacOSX 72 -rw-r--r-- 10 root wheel 203802 Mar 8 06:17 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/string