Why export external(C) generate mangled names?

[mipri]

On Friday, 25 October 2019 at 10:31:15 UTC, Suliman wrote:
> I thought that export extern(C) is needed for C compatibility.

This is only the case for toplevel functions. If there's any 
nesting,
you still get D mangling but you get C calling conventions.

> But When I am compiling follow code
>
> export extern(C)
> {
>     void foo()
>     {
>     }
> }

There's no mangling with this code for me. I have to add a struct 
{}
around it to see mangling.

>
> I am getting section that have mangled names:
>

Look with: objdump -dwr --no-show-raw-insn <filename>

You'll get output like

   000000000042d5f8 <foo>:
     42d5f8:	push   %rbp
     42d5f9:	mov    %rsp,%rbp
     42d5fc:	pop    %rbp
     42d5fd:	retq
   	...

   000000000042d600 <_D4x1244test3barMUZv>:
     42d600:	push   %rbp
     42d601:	mov    %rsp,%rbp
     42d604:	pop    %rbp
     42d605:	retq

for

   extern(C) void foo() {}

   struct test {
       export extern(C) {
           void bar() {}
       }
   }

A note about this was added to the documentation with

https://github.com/dlang/dlang.org/pull/1911/files

but it might be easy to miss since it's not in InterfaceToC