Driver: flip the flag of whether tracking system dependencies #28579
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@swift-ci Please Build Toolchain macOS Platform |
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@swift-ci Please Build Toolchain macOS Platform |
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We should probably have -track-system-dependencies take an optional parameter that says true|false. Removing the flag would be a compatibility break. Also, is there a test case for the .d files and the system deps? Maybe this commit should include a small test case where we see that the size of the .d files does indeed reduce (also as a regression thing in case someone changes the defaults again in the future).
include/swift/Option/Options.td
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| @@ -293,9 +293,9 @@ def profile_stats_entities: Flag<["-"], "profile-stats-entities">, | |||
| def emit_dependencies : Flag<["-"], "emit-dependencies">, | |||
| Flags<[FrontendOption, NoInteractiveOption, DoesNotAffectIncrementalBuild]>, | |||
| HelpText<"Emit basic Make-compatible dependencies files">; | |||
| def track_system_dependencies : Flag<["-"], "track-system-dependencies">, | |||
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I don't think we can remove this flag so easily, that would be a breaking change.
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I understand the concern. However, it seems the build system doesn't specify this flag at all. Also, this driver flag never populates to front-end invocation flags, meaning even if some one specifies the flag, it doesn't change any behavior of the compiler. It should be pretty safe to remove the flag.
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However, it seems the build system doesn't specify this flag at all.
I don't understand which build system are you referring to. Maybe we are not using it but someone external could very well be using it?
Also, this driver flag never populates to front-end invocation flags, meaning even if some one specifies the flag, it doesn't change any behavior of the compiler.
In that case, we should have the doc comment say something like "[Deprecated] We track system dependencies by default, so this flag doesn't do anything. If you want to avoid tracking system dependencies, use -skip-system-dependencies.". We could even add a warning saying that the flag is a no-op and asking the user to remove it.
I don't see what we gain by removing the flag -- we're potentially breaking someone's code for (IMO) no benefit at all.
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macOS Toolchain Install command |
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Using the CI-built toolchain, I've verified that |
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Talking with @jrose-apple more about this, it seems risky to flip the flag at this point and the default value of NOT tracking system dependencies is consistent with Clang's behavior. So it seem the only bug worths fixing here is to pass down |
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@swift-ci please smoke test |
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So the flag works but the driver wasn't passing it down? |
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@DougGregor that's correct. The flag didn't pass down to front-end invocation from driver. |
Tracking system dependencies should be the default setting so we always rebuild after
headers from SDK changes. We should also provide a way to opt-out so builders could reduce
the size of .d files if they are certain SDKs are stable.
rdar://57361722