https://issues.dlang.org/show_bug.cgi?id=23702
--- Comment #5 from Walter Bright <bugzi...@digitalmars.com> --- importc.h has the following lines in it: #undef __has_extension #define __has_extension(x) 0 so: #if __has_extension(gnu_asm) should become: #if 0 I don't know what is going wrong here. Maybe __has_extension cannot be undefined? --