Based on my cmake pull-request(1) to fix the cmake build on OpenBSD, the following question has arisen which is worth analysing?
"It seems OpenBSD has a strange behavior because macro _POSIX_C_SOURCE is a standard! @sizeofvoid What are the errors raised if _POSIX_C_SOURCE or _XOPEN_SOURCE are defined?" -- Marc Chevrier [1]: https://gitlab.kitware.com/cmake/cmake/-/merge_requests/6000 The following code includes the if-defs from cmake with a simple sstream include. $ cat define_test.cxx #if !defined(_WIN32) && !defined(__sun) // POSIX APIs are needed // NOLINTNEXTLINE(bugprone-reserved-identifier) # define _POSIX_C_SOURCE 200809L #endif #if defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__NetBSD__) // For isascii // NOLINTNEXTLINE(bugprone-reserved-identifier) # define _XOPEN_SOURCE 700 #endif #include <sstream> int main () { return 0; } $ clang++ -std=c++17 define_test.cxx # also with c++11/14 In file included from define_test.cxx:16: In file included from /usr/include/c++/v1/sstream:173: In file included from /usr/include/c++/v1/ostream:140: In file included from /usr/include/c++/v1/locale:207: /usr/include/c++/v1/__bsd_locale_fallbacks.h:122:17: error: use of undeclared identifier 'vasprintf'; did you mean 'vsprintf'? int __res = vasprintf(__s, __format, __va); ^ /usr/include/c++/v1/cstdio:124:9: note: 'vsprintf' declared here using ::vsprintf; ^ In file included from define_test.cxx:16: In file included from /usr/include/c++/v1/sstream:173: In file included from /usr/include/c++/v1/ostream:140: In file included from /usr/include/c++/v1/locale:207: /usr/include/c++/v1/__bsd_locale_fallbacks.h:122:27: error: cannot initialize a parameter of type 'char *' with an lvalue of type 'char **' int __res = vasprintf(__s, __format, __va); ^~~ /usr/include/stdio.h:269:21: note: passing argument to parameter here int vsprintf(char *, const char *, __va_list); ^ 2 errors generated Looks like, if "_XOPEN_SOURCE 700" or "_POSIX_C_SOURCE 200809L" is defined we run in this compile error. The question is, is that deliberate?
