[cfe-dev] Should dump methods be LLVM_ATTRIBUTE_USED only in debug builds?

Nico Weber thakis at chromium.org
Fri Dec 27 16:46:34 PST 2013


r151033 and r151037 marked a few dump() methods as LLVM_ATTRIBUTE_USED, and
over time this inspired marking several other dump() methods to be marked
as such too (see e.g. 178400, 182186, 159790, 173548).

I understand that having the dump() methods available in the debugger is
useful, but these annotations prevent the dump() methods from being
dead-stripped, and they end up keeping lots of code alive. For example,
clang-format depends on ASTDumper, TypePrinter, StmtVisitor and related
stuff solely for these dump methods.

Since binaries now get dead-stripped, this leads to measurable bloat:
clang-format goes from 1.7 MB to 1.2 MB if I remove the
LLVM_ATTRIBUTE_USEDs on the 17 dump methods in include/clang – an almost
30% reduction.

Does it make sense to only mark dump methods as LLVM_ATTRIBUTE_USED if
!NDEBUG? (If so, I'm thankful for naming suggestions for this new macro
– LLVM_ATTRIBUTE_USED_IN_DEBUG comes to mind, but is too long. Also, should
this be an LLVM macro or a clang macro?)

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