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Stabilize --extern flag without a path. #64882

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Merged
merged 8 commits into from
Nov 8, 2019
Merged

Stabilize --extern flag without a path. #64882

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b47e3d8
Stabilize --extern flag without a path.
ehuss Sep 28, 2019
e0058ce
Add more --extern tests.
ehuss Sep 30, 2019
4bf411e
Update built-in help for --extern.
ehuss Sep 30, 2019
b54e8ec
Update extern linking documentation.
ehuss Sep 30, 2019
41e051d
Update src/test/ui-fulldeps/pathless-extern-unstable.rs
ehuss Oct 7, 2019
f9e4f0f
Add test for --extern alloc=librustc.rlib
ehuss Oct 8, 2019
845ec5d
Remove docs on --extern metadata precedence.
ehuss Oct 16, 2019
ee459c6
Update for unstable option refactoring.
ehuss Oct 16, 2019
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Remove docs on --extern metadata precedence.
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@ehuss
ehuss committed Nov 7, 2019
commit 845ec5df7af7fa9cc0d4c52ff61b38160e9dcc37
5 changes: 2 additions & 3 deletions src/doc/rustc/src/command-line-arguments.md
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Expand Up @@ -276,9 +276,8 @@ either of the following formats:
such as within the sysroot or via the `-L` flag.
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Do we have tests ensuring that sysroot crates, e.g. private rustc details emit an error when used on a stable compiler? (Also when an explicit path is used to them, not just a search.)

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What happens if both --extern CRATENAME=PATH and --extern CRATENAME are specified for the same CRATENAME? It would be nice to document that.
AFAIR, multiple --extern CRATENAME=PATHs with the same CRATENAME are possible if they lead to different kinds of libraries, like rlib and dylib.

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There are about 30 tests doing various things with pathless --extern (search for // compile-flags:.*--extern).

I have added some more specific tests:

  • run-make-fulldeps/extern-flag-pathless: Shows what happens when you mix pathless with path --extern flags. Also demonstrates the preference of rlib over dylib.
  • ui-fulldeps/pathless-extern-unstable.rs: Shows --extern rustc is not allowed.
  • ui/pathless-extern-ok.rs: Basic test for a sysroot crate.

I don't have a good intuition of how sophisticated rustc tests should be. They are also a bit disorganized, so I didn't know where to stick them, or which style would be preferred. I think the dylib tests should be safe from a cross platform standpoint (I believe they only run on Linux?).

I updated the documentation with some more detail. I never really know how detailed rustc docs should be. I intentionally left the prefer-dynamic algorithm vague. It is described somewhat in src/librustc_metadata/dependency_format.rs. I figure since it is complex, and possibly subject to change, it may not be worthwhile. I can add more or remove some if desired.


The same crate name may be specified multiple times for different crate types.
For loading metadata, `rlib` takes precedence over `rmeta`, which takes
precedence over `dylib`. If both an `rlib` and `dylib` are found, an internal
algorithm is used to decide which to use for linking. The [`-C prefer-dynamic`
If both an `rlib` and `dylib` are found, an internal algorithm is used to
decide which to use for linking. The [`-C prefer-dynamic`
flag][prefer-dynamic] may be used to influence which is used.

If the same crate name is specified with and without a path, the one with the
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