How to Use D's ImportC Compiler in a Program

[Ali Çehreli]

On 10/6/25 5:56 PM, David T. Oxygen wrote:

 > Nothing special.Just a simple Hello-World application.
 > ```c
 > #include<stdio.h>
 > int main(){
 >      printf("Hello World!\n");
 >      return 0;
 > }
 > ```
 > Just like the example on the D website.

I put that code into hello.c and compiled. Yes, there are some warning:

$ dmd hello.c
In file included from <command-line>:
/usr/include/dlang/dmd/importc.h:101:8: warning: undefining "__has_feature"
   101 | #undef __has_feature
       |        ^~~~~~~~~~~~~
/usr/include/dlang/dmd/importc.h:104:8: warning: undefining 
"__has_extension"
   104 | #undef __has_extension
       |        ^~~~~~~~~~~~~~~

I don't know what they mean. My compiler is this:

$ dmd --version
DMD64 D Compiler v2.109.1

But at least the linked program works:

$ ./hello
Hello World!

 > And what in it doesn't matter. The compiler didn't work,no matter what
 > code.

Which compiler? Were there any error messages?

 > I think if my compiler's version is too low to support ImportC...

Possibly. As a reminder, here is the download page.

   https://dlang.org/download.html

Ali