Statically compile libstdc++ everywhere if asked #94719

jonhoo · 2022-03-08T01:05:35Z

PR #93918 made it so that -static-libstdc++ was only set in one place,
and was only set during linking, but accidentally also made it so that
it is no longer passed when building LLD, only when building LLVM
itself. This moves the logic for setting -static-libstdc++ in the
linker flags to configure_cmake so that it takes effect for all CMake
invocations in native.rs.

As a side-effect, this also causes libstdc++ to be statically compiled
into sanitizers, whereas previously the llvm-static-stdcpp flag had no
effect on sanitizers. It also makes it so that LLD will be compiled
statically if llvm-tools-enabled is set, even though previously it was
only linked statically if llvm-static-stdcpp was set explicitly. Both
of these seem like they match expected behavior than what was there
prior to #93918.

rust-highfive · 2022-03-08T01:05:49Z

r? @Mark-Simulacrum

(rust-highfive has picked a reviewer for you, use r? to override)

jonhoo · 2022-03-08T01:13:14Z

I think on balance I've fixed more issues than I've caused 😅 Found this one due to a case where I tried to do a wasm32-wasi build using a rustc distribution built on a new-ish host on a very hold host with an ancient GLIBCXX, and it errored with a GLIBCXX version mismatch since was32 targets link with rust-lld by default.

jonhoo · 2022-03-08T01:29:06Z

For reference, the code that used to live in configure_cmake that used to do this is: https://github.com/rust-lang/rust/pull/93918/files#diff-ca6526d91d41c31fad645c46417e0f1ce61e324542994e8c8b72b1f7a08c91bdL527

And, actually, looking at it it used to apply to sanitizers as well, so I think the only actual semantics change here is that -static-libstdc++ will apply to LLD and sanitizers if llvm-tools-enabled even if llvm-static-stdcpp isn't.

PR rust-lang#93918 made it so that `-static-libstdc++` was only set in one place, and was only set during linking, but accidentally also made it so that it is no longer passed when building LLD or sanitizers, only when building LLVM itself. This moves the logic for setting `-static-libstdc++` in the linker flags back to `configure_cmake` so that it takes effect for all CMake invocations in `native.rs`. As a side-effect, this also causes libstdc++ to be statically compiled into sanitizers and LLD if `llvm-tools-enabled` is set but `llvm-static-stdcpp` is not, even though previously it was only linked statically if `llvm-static-stdcpp` was set explicitly. But that seems more like the expected behavior anyway.

jonhoo · 2022-03-08T01:31:26Z

I force-pushed a change that just changes the commit message to be accurate with respect to sanitizers.

Mark-Simulacrum · 2022-03-08T02:14:42Z

src/bootstrap/native.rs

@@ -576,6 +564,18 @@ fn configure_cmake(
        ldflags.push_all(&flags);
    }

+    // For distribution we want the LLVM tools to be *statically* linked to libstdc++.
+    // We also do this if the user explicitly requested static libstdc++.
+    if builder.config.llvm_tools_enabled || builder.config.llvm_static_stdcpp {


We blanket enable llvm-static-stdcpp in our CI (see

rust/src/ci/run.sh

Line 72 in 03918ba

RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-llvm-static-stdcpp"

), so I'm wondering if it makes sense to remove the llvm-tools enablement here -- it's not obvious to me that it should be present.

It looks like that was originally added in #50336, but it seems like an odd thing to force opt-in users of the build system to with an orthogonal flag. Maybe you have a better sense here though!

I think this somewhat makes this PR a clearer "yes" to me, since if we're migrating to a simpler story of only enabling static stdcpp if asked explicitly, then doing that for everything makes sense. But if that's gated on llvm tools being enabled, it feels weird for that to apply to "not tools".

It's a tough call. When you need llvm-tools, you'll very often want them with static libstdc++, because otherwise they may just not run on whatever host you try running them on, and you won't be able to tell until a user with an old host is bitten by it. But at the same time, as you point out, there's no fundamental reason they need to be coupled (at least as far as I can tell), which suggests the two flags should be decoupled. I think of this as an anti-footgun of having llvm-tools imply static-libstdc++ because builders may not have thought through the implications of not linking it statically (they may not even be aware of the static-stdcpp flag).

Which is all to say — I think decoupling them gives more flexibility to builders, but at the cost of making it harder to get to a functioning build for someone who's trying to replicate the upstream build process. Which of those is more important, I'm not sure.

Hm. Yes, that makes sense. I think we should probably be changing the default for static stdcpp, then, rather than specifically checking tools here, but that seems like a change that needs it's own PR.

Oh, yeah, I like that idea! Can submit a PR for that tomorrow. And then you'd want this PR to just switch on llvm_static_stdcpp?

Actually, I think we should do a separate PR that changes the if condition to just be llvm_static_stdcpp and flips its default. Otherwise, in the interrim (however short) we'll be changing the behavior of the code.

tmiasko · 2022-03-08T16:18:10Z

As a side-effect, this also causes libstdc++ to be statically compiled into sanitizers

Sanitizers don't use or link to the C++ standard library. It would be better to avoid adding -static-libstdc++ there since leads to warning about unused arguments. Though, it seems acceptable since -nodefaultlibs / -nostdlib++ take precedence.

jonhoo · 2022-03-08T17:00:43Z

Prior to #93918, we were passing -static-libstdc++ to the sanitizers too, but we were doing so through both CXXFLAGS and LDFLAGS, which caused a lot more noise. Now that it's just LDFLAGS, I'm inclined to keep the logic in just one place (configure_cmake). This also guards us against the hypothetical case where the sanitizers do for some reason need something from stdc++ in the future.

jonhoo · 2022-03-09T04:13:55Z

I actually wonder if this needs a backport (along with #94466), since otherwise users of 1.60 will just get #93918, which in turn means their lld won't be statically linked with libstdc++. It should only affect stable users who are linking with rust-lld and running on fairly old platforms, but that number probably isn't zero.

Mark-Simulacrum · 2022-03-09T14:13:47Z

Yeah, I'm going to go ahead and unilaterally approve for beta backport, I think it makes sense to roll these two into one change from user's perspective. The alternative I think would be to back out #93918, but that seems worse to me. In any case, these changes should be fairly well-tested since they affect our shipped artifacts, and if they cause problems for distros they can locally revert fairly easily (since it just touches rustbuild).

@bors r+ rollup

bors · 2022-03-09T14:13:49Z

📌 Commit b328688 has been approved by Mark-Simulacrum

…mulacrum Statically compile libstdc++ everywhere if asked PR rust-lang#93918 made it so that `-static-libstdc++` was only set in one place, and was only set during linking, but accidentally also made it so that it is no longer passed when building LLD, only when building LLVM itself. This moves the logic for setting `-static-libstdc++` in the linker flags to `configure_cmake` so that it takes effect for all CMake invocations in `native.rs`. As a side-effect, this also causes libstdc++ to be statically compiled into sanitizers, whereas previously the `llvm-static-stdcpp` flag had no effect on sanitizers. It also makes it so that LLD will be compiled statically if `llvm-tools-enabled` is set, even though previously it was only linked statically if `llvm-static-stdcpp` was set explicitly. Both of these seem like they match expected behavior than what was there prior to rust-lang#93918.

Rollup of 7 pull requests Successful merges: - rust-lang#93950 (Use modern formatting for format! macros) - rust-lang#94274 (Treat unstable lints as unknown) - rust-lang#94368 ([1/2] Implement macro meta-variable expressions) - rust-lang#94719 (Statically compile libstdc++ everywhere if asked) - rust-lang#94728 (Only emit pointer-like metadata for `Box<T, A>` when `A` is ZST) - rust-lang#94790 (enable portable-simd doctests in Miri) - rust-lang#94811 (Update browser-ui-test version) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

jonhoo · 2022-03-11T01:52:39Z

Wooo! Let me get you a PR that changes the default 👍

Previously, the static-libstdcpp setting was tied to llvm-tools such that enabling the latter always enabled the latter. This seems unfortunate, since it is entirely reasonable for someone to want to _not_ statically link stdc++, but _also_ want to build the llvm-tools. This patch therefore separates the two settings such that neither implies the other. On its own, that would change the default behavior in a way that's likely to surprise users. Specifically, users who build llvm-tools _likely_ want those tools to be statically compiled against libstdc++, since otherwise users with older GLIBCXX will be unable to run the vended tools. So, we also flip the default for the `static-libstdcpp` setting such that builds always link statically against libstdc++ by default, but it's _possible_ to opt out. See also rust-lang#94719.

jonhoo · 2022-03-11T02:06:11Z

Opened #94832

bootstrap: untangle static-libstdcpp & llvm-tools Previously, the static-libstdcpp setting was tied to llvm-tools such that enabling the latter always enabled the latter. This seems unfortunate, since it is entirely reasonable for someone to want to _not_ statically link stdc++, but _also_ want to build the llvm-tools. This patch therefore separates the two settings such that neither implies the other. On its own, that would change the default behavior in a way that's likely to surprise users. Specifically, users who build llvm-tools _likely_ want those tools to be statically compiled against libstdc++, since otherwise users with older GLIBCXX will be unable to run the vended tools. So, we also flip the default for the `static-libstdcpp` setting such that builds always link statically against libstdc++ by default, but it's _possible_ to opt out. See also rust-lang#94719.

…ulacrum [beta] backports * Update LLVM submodule rust-lang#94764 * Statically compile libstdc++ everywhere if asked rust-lang#94719 * Downgrade #[test] on macro call to warning rust-lang#94624 * Delay bug in expr adjustment when check_expr is called multiple times rust-lang#94596 * bootstrap: correct reading of flags for llvm rust-lang#94466 * Check method input expressions once rust-lang#94438 * remove feature gate in control_flow examples rust-lang#94283 r? `@Mark-Simulacrum`

rust-highfive assigned Mark-Simulacrum Mar 8, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 8, 2022

jonhoo force-pushed the enable-static-lld branch from 4542075 to b328688 Compare March 8, 2022 01:31

Mark-Simulacrum reviewed Mar 8, 2022

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 9, 2022

Mark-Simulacrum added beta-accepted Accepted for backporting to the compiler in the beta channel. beta-nominated Nominated for backporting to the compiler in the beta channel. labels Mar 9, 2022

Mark-Simulacrum mentioned this pull request Mar 9, 2022

bootstrap: correct reading of flags for llvm #94466

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Rollup of 8 pull requests #94771

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Rollup of 7 pull requests #94774

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Rollup of 16 pull requests #94784

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Rollup of 7 pull requests #94801

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Rollup of 7 pull requests #94807

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Rollup of 7 pull requests #94824

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bors merged commit 1cf8793 into rust-lang:master Mar 11, 2022

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bootstrap: untangle static-libstdcpp & llvm-tools #94832

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1.46.0 fails to build with llvm-libunwind enabled #76020

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[beta] backports #94933

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Statically compile libstdc++ everywhere if asked #94719

Statically compile libstdc++ everywhere if asked #94719

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Statically compile libstdc++ everywhere if asked #94719

Statically compile libstdc++ everywhere if asked #94719

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