...GNUC__ means gnu C dialect?

--- cjanet.c ---
#undef __GNUC__
#include "janet.c"
---
dmd -P-I...

...in it to do that, though I suspect that an:

    #undef _FORTIFY_SOURCE

might work?

--

...or recognized by ImportC, it is just #undef'd away in importc.h.

You can...

...h has the following lines in it:

    #undef __has_extension
    #define __has_extension(x) 0...

...d.en/exceptions.html#ix_exceptions.try
[2]: https://c-faq.com/ansi/undef.html

...C's -D, -U switches and #define/#undef system is infinitely adjustable, and programmers inevitably...

...Buclaw <ibuclaw@gdcproject.org> ---
Discrepancy is documented undef Extensions/enum base types.

https://dlang.org...

...from Iain Buclaw <ibuclaw@gdcproject.org> ---
Bad #undef/#define of reserved macros has been reverted...

...80:8: warning:
undefining "__has_builtin"
   80 | #undef __has_builtin
      |        ^~~~~~~~~~~~~
----
diff:
----
-
+In file included from...

...80:8:
warning: undefining "__has_builtin"
   80 | #undef __has_builtin
      |        ^~~~~~~~~~~~~
/usr/include/x86_64-linux...