rustc: Implement #[link(cfg(..))] and crt-static #37545

alexcrichton · Nov 3, 2016

This commit is an implementation of RFC 1721 which adds a new target feature
to the compiler, crt-static, which can be used to select how the C runtime for
a target is linked. Most targets dynamically linke the C runtime by default with
the notable exception of some of the musl targets.

This commit first adds the new target-feature, crt-static. If enabled, then
the cfg(target_feature = "crt-static") will be available. Targets like musl
will have this enabled by default. This feature can be controlled through the
standard target-feature interface, -C target-feature=+crt-static or
-C target-feature=-crt-static.

Next this adds an gated and unstable #[link(cfg(..))] feature to enable the
crt-static semantics we want with libc. The exact behavior of this attribute
is a little squishy, but it's intended to be a forever-unstable
implementation detail of the liblibc crate.

Specifically the #[link(cfg(..))] annotation means that the #[link]
directive is only active in a compilation unit if that cfg value is satisfied.
For example when compiling an rlib, these directives are just encoded and
ignored for dylibs, and all staticlibs are continued to be put into the rlib as
usual. When placing that rlib into a staticlib, executable, or dylib, however,
the cfg is evaluated as if it were defined in the final artifact and the
library is decided to be linked or not.

Essentially, what'll happen is:

On MSVC with -C target-feature=-crt-static, the msvcrt.lib library will be
linked to.
On MSVC with -C target-feature=+crt-static, the libcmt.lib library will be
linked to.
On musl with -C target-feature=-crt-static, the object files in liblibc.rlib
are removed and -lc is passed instead.
On musl with -C target-feature=+crt-static, the object files in liblibc.rlib
are used and -lc is not passed.

This commit does not include an update to the liblibc module to implement
these changes. I plan to do that just after the 1.14.0 beta release is cut to
ensure we get ample time to test this feature.

cc #37406

rust-highfive · Nov 3, 2016

r? @eddyb

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alexcrichton · Nov 3, 2016

r? @brson

alexcrichton · Nov 3, 2016

I tested bootstrapping this with this commit: alexcrichton/libc@5699631. With that I was able to produce static/dynamic MSVC and musl binaries with the flip of this switch, so it's at least confirmed to work there!

retep998 · Nov 3, 2016

If possible, it would be really nice to have options for the debug versions of the CRT, msvcrtd.lib and libcmtd.lib.

bors · Nov 6, 2016

☔️ The latest upstream changes (presumably #37597) made this pull request unmergeable. Please resolve the merge conflicts.

bors · Nov 9, 2016

☔️ The latest upstream changes (presumably #37670) made this pull request unmergeable. Please resolve the merge conflicts.

alexcrichton · Nov 10, 2016

Ok, I've updated this and now that beta has been released I went ahead and included the update to liblibc.

bors · Nov 10, 2016

☔️ The latest upstream changes (presumably #37463) made this pull request unmergeable. Please resolve the merge conflicts.

bors · Nov 10, 2016

☔️ The latest upstream changes (presumably #37542) made this pull request unmergeable. Please resolve the merge conflicts.

brson · Nov 10, 2016

@bors r+

bors · Nov 10, 2016

📌 Commit aede832 has been approved by brson

brson · Nov 11, 2016

@bors r-

Seems like we should feature-gate the crt-static target feature so it can't be mentioned on the command line yet.

alexcrichton · Nov 11, 2016

@bors: r=brson

Hooked up -C target-feature=+crt-static to -Z unstable-options

bors · Nov 11, 2016

📌 Commit 791763b has been approved by brson

alexcrichton · Nov 15, 2016

@bors: r=brson

bors · Nov 15, 2016

📌 Commit 957d3e9 has been approved by brson

bors · Nov 15, 2016

⌛️ Testing commit 957d3e9 with merge a4add40...

bors · Nov 15, 2016

💔 Test failed - auto-win-gnu-32-opt-rustbuild

alexcrichton · Nov 15, 2016

@bors: r=brson

bors · Nov 15, 2016

📌 Commit 9a9189c has been approved by brson

bors · Nov 15, 2016

⌛️ Testing commit 9a9189c with merge fdb5fa1...

bors · Nov 15, 2016

💔 Test failed - auto-win-gnu-32-opt-rustbuild

alexcrichton · Nov 16, 2016

@bors: r=brson

bors · Nov 16, 2016

📌 Commit 06242ff has been approved by brson

bors · Nov 16, 2016

⌛️ Testing commit 06242ff with merge 9d4b6fa...

bors · Nov 16, 2016

rust-highfive assigned eddyb Nov 3, 2016

rust-highfive assigned brson and unassigned eddyb Nov 3, 2016

japaric referenced this pull request Nov 4, 2016
Open
How to compile rust in a musl libc based linux system #31322

alexcrichton force-pushed the alexcrichton:crt-static branch from 4487091 to 6da63c8 Nov 6, 2016

alexcrichton added a commit to alexcrichton/libc that referenced this pull request Nov 10, 2016

Use `#[link(cfg(..))]` in preparation for libstd
In preparation for rust-lang/rust#37545 this is adding the appropriate directives to libc to get included.

f9323d1

alexcrichton referenced this pull request Nov 10, 2016
Merged
Use `#[link(cfg(..))]` in preparation for libstd #446

alexcrichton force-pushed the alexcrichton:crt-static branch from 6da63c8 to f5c9fb6 Nov 10, 2016

alexcrichton force-pushed the alexcrichton:crt-static branch from f5c9fb6 to 0d329a2 Nov 10, 2016

alexcrichton force-pushed the alexcrichton:crt-static branch 2 times, most recently from 51af985 to aede832 Nov 10, 2016

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alexcrichton force-pushed the alexcrichton:crt-static branch 2 times, most recently from 21d77be to 791763b Nov 11, 2016

alexcrichton force-pushed the alexcrichton:crt-static branch from 957d3e9 to 9a9189c Nov 15, 2016

alexcrichton force-pushed the alexcrichton:crt-static branch from 9a9189c to 06242ff Nov 16, 2016

This was referenced Nov 16, 2016

Closed

Do not link statically against libc by default for musl targets rust-lang/libc#314

Closed

Can't statically link MSVC runtime rust-lang/libc#290

bors merged commit 06242ff into rust-lang:master Nov 16, 2016
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Merged

add --crate-type metadata #37681

Merged

Support `use`ing externally defined macros behind `#![feature(use_extern_macros)]` #37732

Merged

Implement the `loop_break_value` feature. #37487

retep998 referenced this pull request Nov 18, 2016
Closed
add to package repositories #10

urschrei added a commit to urschrei/lonlat_bng that referenced this pull request Nov 20, 2016

Switch back to dylib
-gnu is somewhat broken using cdylib: rust-lang/rust#37530 But we should be able to statically link msvcrt: rust-lang/rust#37545

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6c640e6

retep998 referenced this pull request Dec 14, 2016
Open
Don't get memcpy, memmove, memcmp, memset, and strlen from msvcrt.dll #29130

alexcrichton deleted the alexcrichton:crt-static branch Dec 19, 2016

jdm referenced this pull request Jan 23, 2017
Open
rustc always links against non-debug Windows runtime #39016

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rustc: Implement #[link(cfg(..))] and crt-static #37545

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alexcrichton force-pushed the alexcrichton:crt-static branch from `4487091` to `6da63c8` Nov 6, 2016

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alexcrichton force-pushed the alexcrichton:crt-static branch from `f5c9fb6` to `0d329a2` Nov 10, 2016

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brson commented Nov 11, 2016 •

edited

alexcrichton force-pushed the alexcrichton:crt-static branch 2 times, most recently from `21d77be` to `791763b` Nov 11, 2016

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alexcrichton force-pushed the alexcrichton:crt-static branch from `9a9189c` to `06242ff` Nov 16, 2016

bors merged commit `06242ff` into rust-lang:master Nov 16, 2016
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