https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117210
--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Dimitry Andric from comment #10) > Yes, that works. So maybe we were lucky that cdefs.h got transitively > included in the past, but not anymore? No. <cmath> basically does this: #include <bits/c++config.h> // which includes: #include <bits/os_defines.h> // which defines: #define _GLIBCXX_USE_C99_LONG_LONG_DYNAMIC (_GLIBCXX_USE_C99_DYNAMIC || !defined __LONG_LONG_SUPPORTED) # include <math.h> // which includes #include <sys/cdefs.h> // which defines #define __LONG_LONG_SUPPORTED // ... #if ! _GLIBCXX_USE_C99_LONG_LONG_DYNAMIC As I said in comment 7, the old definition of the DYNAMIC macro meant it did not care about the value of __LONG_LONG_SUPPORTED until the DYNAMIC macro was used, which was after <sys/cdefs.h>. So __LONG_LONG_SUPPORTED was defined then. The new definition of the DYNAMIC macro expands the value of __LONG_LONG_SUPPORTED immediately, before cdefs.h has been defined. > That said, sys/cdefs.h is really a bit of a FreeBSD implementation detail. Which is why it should be included in the bsd/freebsd/os_defines.h file, not elsewhere. > It does get included automatically with most of the regular system headers, > including <stdlib.h>. But those aren't included until after <bits/c++config.h> which includes os_defines.h
