[PATCH] D157794: [Driver] Make /Zi and /Z7 aliases of -g rather than handling them specially

[Martin Storsjö via Phabricator via cfe-commits]

mstorsjo added inline comments.


================
Comment at: clang/test/Driver/cl-options.c:567
 
-// This test was super sneaky: "/Z7" means "line-tables", but "-gdwarf" occurs
-// later on the command line, so it should win. Interestingly the cc1 arguments
-// came out right, but had wrong semantics, because an invariant assumed by
-// CompilerInvocation was violated: it expects that at most one of {gdwarfN,
-// line-tables-only} appear. If you assume that, then you can safely use
-// Args.hasArg to test whether a boolean flag is present without caring
-// where it appeared. And for this test, it appeared to the left of -gdwarf
-// which made it "win". This test could not detect that bug.
+// If We specify both /Z7 and -gdwarf we should get dwarf, not codeview.
 // RUN: %clang_cl /Z7 -gdwarf /c -### -- %s 2>&1 | FileCheck -check-prefix=Z7_gdwarf %s
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smeenai wrote:
> bogner wrote:
> > smeenai wrote:
> > > bogner wrote:
> > > > rnk wrote:
> > > > > I think Meta folks depend on a mode that emits both codeview and DWARF. + at smeenai
> > > > Hopefully if that's the case there's a better test somewhere than this one that discusses in detail how `/Z7` is an alias for `-gline-tables-only`, which hasn't been true since 2017.
> > > Thanks for the headers up :) We don't depend on that mode any more though, so no problems on our end.
> > Also note that this change does not affect what happens if we specify both `-gcodeview` and `-gdwarf` together. That continues to pass both `-gcodeview` and `-dwarf-version=...` to `clang -cc1`. However, I don't see any tests that actually check that behaviour, so if that is a mode that's useful to keep working we definitely have some gaps there.
> > 
> > This change means that if you want to ask `-cc1` for dwarf *and* codeview with `/Z7` or `/Zi`, you'll need to specify `-gdwarf` and `-gcodeview` now. This matches how you would get both sets of options to render with `-g`, which I think makes sense.
> Yeah, that sounds good. IIRC when we were using the joint codeview + DWARF mode it was with the gcc-style Clang driver and not clang-cl, and we passed `-gdwarf -gcodeview` or similar to enable it anyway. We don't need that anymore though; @mstorsjo would know if there's anything on the MinGW side that cares for it.
I'm not aware of mingw usecases of using both codeview and DWARF at the same time - I've occasionally mentioned that I know some people do use that, but I haven't actually guided anybody into doing it.

For mingw, as long as `-g -gcodeview` on the driver level generates codeview (and not DWARF) like it used to, mingw should be fine.


Repository:
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  https://reviews.llvm.org/D157794/new/

https://reviews.llvm.org/D157794