I've been trying to compile a trivial program (extern C int main() {return 0;}) without linking parts of the C runtime with no success.

I compile with dmd -debuglib= -defaultlib= -v -L=/INFORMATION -betterC but optlink shows a lot of things from snn.lib being pulled in and the resultant executable is about 12kb. I also replaced object.d with an empty module.

If I pass /nodefaultlib to the linker I get warning 23: no stack and __acrtused_con is undefined so the linker fails with no start address.

Is it possible to completely remove the C runtime on windows, and if so how? Sorry for the sloppily formatted post.

On Sunday, 15 July 2018 at 20:29:29 UTC, tcb wrote:
> Is it possible to completely remove the C runtime on windows, and if so how?

This works for me:

extern(C) int mainCRTStartup() { return 0; }

dmd -m32mscoff -betterC -L/subsystem:CONSOLE main.d

=> 1.5 kB .exe.

On 7/15/2018 1:29 PM, tcb wrote:
> I've been trying to compile a trivial program (extern C int main() {return 0;}) without linking parts of the C runtime with no success.

Declaring a C function called "main" causes the C runtime library to be pulled in. After all, main() is not the program entry point, as main() requires a number of things to be set up first (such as argc and argv).

Call the function something else, and compile with -betterC.

Thank you both, that clarifies a lot!

On 7/15/2018 2:46 PM, tcb wrote:
> Thank you both, that clarifies a lot!

You can set the start address with the DMC C compiler using a #pragma:

  https://www.digitalmars.com/ctg/pragmas.html#startaddress

but currently that isn't directly settable with the DMD compiler.

You can see how it is used in this file of the DMC runtime library:

  https://github.com/DigitalMars/dmc/blob/master/src/WIN32/constart.c#L88

On Sunday, 15 July 2018 at 20:29:29 UTC, tcb wrote:
> I've been trying to compile a trivial program (extern C int main() {return 0;}) without linking parts of the C runtime with no success.
>
> I compile with dmd -debuglib= -defaultlib= -v -L=/INFORMATION -betterC but optlink shows a lot of things from snn.lib being pulled in and the resultant executable is about 12kb. I also replaced object.d with an empty module.
>
> If I pass /nodefaultlib to the linker I get warning 23: no stack and __acrtused_con is undefined so the linker fails with no start address.
>
> Is it possible to completely remove the C runtime on windows, and if so how? Sorry for the sloppily formatted post.

I recently created an issue that included an example that allows you to compile a Hello World program on linux x64 without the c standard library, druntime or phobos.

https://issues.dlang.org/show_bug.cgi?id=19078

You can modify it to run on windows as well.  I'm not sure if the _start assembly implementation would be the same on windows.  Try it out and let me know how it works.