https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103877
Bug ID: 103877 Summary: libstdc++ docs give a bad recommendation for printing C++ defines Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: web Assignee: unassigned at gcc dot gnu.org Reporter: blubban at gmail dot com Target Milestone: --- https://gcc.gnu.org/onlinedocs/libstdc++/faq.html#faq.predefined > You can also run g++ -E -dM - < /dev/null" to display a > list of predefined macros for any particular installation. Issue 1: The unmatched quote. Issue 2: g++ -E defaults to C mode, where _GNU_SOURCE is, in fact, not defined. The correct command is g++ -E -dM -xc++ - < /dev/null