[PATCH] D76482: [lld][ELF] Provide optional hidden symbol for build ID

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

I think we should be a bit more careful proposing a new reserved symbol (symbol assignment even in the absence of a SECTIONS command) and think whether it will be useful after 5 years.

In FreeBSD, their linker script defines:

  .note.gnu.build-id : {
    PROVIDE (__build_id_start = .);
    *(.note.gnu.build-id)
    PROVIDE (__build_id_end = .);
  }

We need `__build_id_end` because the size of .build-id can evolve. While I think sha1 is good enough for many use cases, I can imagine someone may want more bits.

OK, I can imagine there are use cases that an external linker script is not desired. There is another perfect alternative: parse PT_NOTE and extract NT_GNU_BUILD_ID.



================
Comment at: lld/test/ELF/build-id.s:8
 
+# RUN: ld.lld --build-id %t -o %t2
+# RUN: llvm-objdump -t -h %t2 | FileCheck --check-prefix=SYMBOL %s
----------------
Don't repeat lld command.


================
Comment at: lld/test/ELF/build-id.s:9
+# RUN: ld.lld --build-id %t -o %t2
+# RUN: llvm-objdump -t -h %t2 | FileCheck --check-prefix=SYMBOL %s
+
----------------
llvm-objdump -h output does not match GNU objdump. This has been a headache for many projects. llvm-readelf -S -s is usually a bette replacement.


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https://reviews.llvm.org/D76482