[all-commits] [llvm/llvm-project] a169d4: [LLD] [COFF] Error out if the runtime pseudo reloc...

[Martin Storsjö via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a169d4c2e974ceb20b86faea3fa4ac286a1d44e8
      https://github.com/llvm/llvm-project/commit/a169d4c2e974ceb20b86faea3fa4ac286a1d44e8
  Author: Martin Storsjö <martin at martin.st>
  Date:   2024-04-16 (Tue, 16 Apr 2024)

  Changed paths:
    M lld/COFF/Writer.cpp
    M lld/test/COFF/autoimport-arm-data.s
    M lld/test/COFF/autoimport-arm64-data.s
    M lld/test/COFF/autoimport-gnu-implib.s
    A lld/test/COFF/autoimport-handler-func.s
    M lld/test/COFF/autoimport-warn.s
    M lld/test/COFF/autoimport-x86.s

  Log Message:
  -----------
  [LLD] [COFF] Error out if the runtime pseudo relocation function is missing (#88573)

When then linker creates runtime pseudo relocations, it places them in a
list with the assumption that the runtime will fix these relocations
later, when the image gets loaded. If the relevant runtime function
doesn't seem to be present in the linked image, error out.

Normally when linking the mingw-w64 runtime libraries, this function
always is available. However, if linking without including the mingw-w64
CRT startup files, and the image needs runtime pseudo relocations, make
it clear that this won't work as expected at runtime.

With ld.bfd, this situation is a hard error too; ld.bfd adds an
undefined reference to this symbol if runtime pseudo relocations are
needed.

A later alternative would be to actually try to pull in the symbol (if
seen in a static library, but not included yet). This would allow
decoupling the function from the main mingw-w64 CRT startup code (making
it optional, only running if the linker actually produced runtime pseudo
relocations).

Doing that would require restructuring the lld code (gathering pseudo
relocations earlier, then loading the relocator function, then pulling in
more object files to satisfy the dependencies of the relocator) though.

Also, ld.bfd doesn't currently successfully pull in more object files to
satisfy the dependency on _pei386_runtime_relocator, so with that in
mind, there's not much extra value in making LLD do it currently either;
we can't make such a change in mingw-w64's CRT until both linkers
handle it.

This fixes one issue brought up in
https://github.com/llvm/llvm-project/issues/84424.



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