Can't add the allocated section to elf file using inline assembly

[Fangrui Song]

On 2019-11-08, drug wrote:
>On 11/7/19 6:20 PM, kinke wrote:
>>On Thursday, 7 November 2019 at 14:58:24 UTC, drug wrote:
>>>What can be the reason of this?
>>
>>--gc-sections applied by LDC by default - use 
>>-disable-linker-strip-dead to keep unreferenced sections.
>
>Thank you very much! It works now.
>
>What is the best way to create a reference to this section to prevent 
>its stripping?

Use the .reloc directive and an R_*_NONE (no-op) relocation to reference
the section from a known-live section (e.g. main). As an example:

import ldc.llvmasm;

void foo() {
   __asm!void(
     `.pushsection .stapsdt.base,"aG",%progbits,.stapsdt.base,comdat
      .weak _.stapsdt.base
      .hidden _.stapsdt.base
      _.stapsdt.base: .space 1
      .size _.stapsdt.base,1
      .popsection`, ""
   );
}

void main() {
   __asm!void(".reloc 0, R_X86_64_NONE, .stapsdt.base", "");
}

This works with GNU ld, gold and lld, and it does not require
-disable-linker-strip-dead. Parsing R_*_NONE requires llvm 9 or newer.
I added .reloc for x86/ARM/AArch64/PowerPC in May 2019. R_MIPS_NONE
worked even before that time.