MaskRay wrote: > > > I don't really understand the rationale for this, and it's kind of > > > annoying. Most of the compiler's flags behave in the "last one wins" > > > fashion (such as `-O2` and `-O0`) and it's always been convenient to add > > > the flag you want at the end. Why treat action flags any differently? > > > Also, even if this is worthwhile for some reason I haven't considered, > > > why is it an error rather than a warning? > > > > > > @bogner Some action options are shared between driver and cc1 but the > > behaviors could be quite different. See my example in the description. > > ``` > > %clang_cc1 -S -emit-llvm a.c # -S is overridden > > %clang_cc1 -emit-llvm -S a.c # -emit-llvm is overridden > > %clang_cc1 -fsyntax-only -S a.c # -fsyntax-only is overridden > > ``` > > > > > > > > > > > > > > > > > > > > > > > > The strictness helps ensure that `%clang_cc1` tests do not have misleading, > > overridden action options. > > So the oddity here really is the driver, which translates both `-S > -emit-llvm` and `-emit-llvm -S` to `-emit-llvm-bc` in the `-cc1` invocation. > Before this change the cc1 invocation treated `-S` and the various > `-emit-XYZ` flags consistently with other options like `-O`, `-g`, and most > `-f` group flags, letting later ones override earlier. > > I suppose that it's somewhat reasonable to warn users that `-cc1` behaves > differently than the driver for certain combinations of `-S` and > `-emit-llvm`, and it's probably too impactful of a change to change the > driver. Even so, I really think this should just be a warning and not a hard > error.
The driver behavior isn't that odd. "Last option wins" applies to `-ffoo -fno-foo` but only in a few cases `-ffoo -fbar`. cc1 reuses the option names but gives them different semantics (last action group wins). Before this patch and the associated cleanups, a lot of tests had more than one actions and the authors were unaware the issue, e.g. `-ast-dump -emit-pch` (`-ast-dump` is ignored), `-emit-obj -emit-llvm` (`-emit-obj` is ignored). With this error behavior, these `%clang_cc1` usage mistakes will be caught. A warning would not provide protection... https://github.com/llvm/llvm-project/pull/91140 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
