[PATCH] D142408: [SanitizerBinaryMetadata] Declare callbacks extern weak

[Marco Elver via Phabricator via llvm-commits]

melver created this revision.
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Declare callbacks extern weak (if no existing declaration exists), and
only call if the function address is non-null.

This allows to attach semantic metadata to binaries where no user of
that metadata exists, avoiding to have to link empty stub callbacks.

Once the binary is linked (statically or dynamically) against a tool
runtime that implements the callbacks, the respective callbacks will be
called. This vastly simplifies gradual deployment of tools using the
metadata, esp. avoiding having to recompile large codebases with
different compiler flags (which negatively impacts compiler caches).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142408

Files:
  compiler-rt/test/metadata/nocallback.cpp
  llvm/include/llvm/Transforms/Utils/ModuleUtils.h
  llvm/lib/Transforms/Instrumentation/SanitizerBinaryMetadata.cpp
  llvm/lib/Transforms/Utils/ModuleUtils.cpp
  llvm/test/Instrumentation/SanitizerBinaryMetadata/atomics.ll

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