[PATCH] D120455: [CommandLine] Remove `may only occur zero or one times!` error

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
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Command line utilities using getopt/getopt_long typically let the last option
win. This makes overridding convenient if there is a global setting.
Clang driver options match the behavior with `getLastArg`.
However, cl::opt diverges from the traditional behavior by reporting an error,
therefore makeing workaround difficult:

  % clang -c a.c -mllvm -disable-binop-extract-shuffle -mllvm -disable-binop-extract-shuffle
  clang (LLVM option parsing): for the --disable-binop-extract-shuffle option: may only occur zero or one times!
  % clang -c a.c -mllvm --scalar-evolution-max-arith-depth=32 -mllvm --scalar-evolution-max-arith-depth=32
  clang (LLVM option parsing): for the --scalar-evolution-max-arith-depth option: may only occur zero or one times!

I have seen such needs several times and the `may only occur zero or one
times!` error is quite a pain. I think cl::opt should match the traditional
behavior.

Removing the error is a degraded error checking experience. I think this error
checking behavior, if desirable, should be enabled explicitly by tools. Users
preferring the behavior can figure out a way to do so. I am biased toward
matching the traditional behavior.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D120455

Files:
  llvm/lib/Support/CommandLine.cpp
  llvm/test/tools/llvm-libtool-darwin/create-static-lib.test
  llvm/test/tools/llvm-libtool-darwin/deterministic-library.test
  llvm/test/tools/llvm-libtool-darwin/filelist.test
  llvm/test/tools/llvm-libtool-darwin/invalid-input-output-args.test
  mlir/test/Pass/pipeline-options-parsing.mlir

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