Fix debuginfo compression in bootstrap by Kobzol · Pull Request #158169 · rust-lang/rust

Kobzol · 2026-06-20T09:29:48Z

Found through https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/weird.20code.20in.20fill_target_compiler/with/604588655.

This PR solves a few issues with debuginfo compression in bootstrap.

The main issue was that debuginfo compression through the -gz flag wasn't enabled, by mistake.

When cc-rs checks if a compiler flag is supported, it tries to read out_dir to generate the source file in. However, when this option is not set, then the check silently fails and the flag is considered to be unsupported. Since we didn't set out_dir, all such added flags were simply ignored.

Normally, it reads OUT_DIR, which is fine if cc-rs is used within a build script. But if it is used elsewhere, then this is a pretty gnarly footgun in cc-rs, because the failure is completely silent. CC @madsmtm or @NobodyXu in case you have thoughts on that :)

After that was fixed, I had to change the used compression flag from -gz to --compress-debug-sections, to support both BFD and LLD linkers.

And to solve it properly, and allow dist CI jobs to configure debuginfo compression for all targets that they build, I added a new bootstrap option to configure debuginfo compression.

I wanted the flag to be configurable both globally and per target. At the same time, the flag applies both to C/C++ and Rust. We currently don't have such config area in bootstrap.toml, and [build] didn't seem like the right place, so I shoved it into [rust] (while documenting that it also applies to C/C++).

r? @bjorn3

try-job: dist-x86_64-msvc
try-job: dist-x86_64-apple
try-job: dist-x86_64-linux
try-job: dist-various-1
try-job: dist-various-2

bjorn3 · 2026-06-20T09:43:11Z

Thanks!

@bors r+

rust-bors · 2026-06-20T09:43:14Z

📌 Commit 1bc29dc has been approved by bjorn3

It is now in the queue for this repository.

@madsmtm

Fix cc rs flag if supported Found in https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/weird.20code.20in.20fill_target_compiler/with/604588655. When `cc-rs` checks if a compiler flag is supported, it tries to read `out_dir` to generate the source file in. However, when this option is not set, then the check silently fails and the flag is considered to be unsupported. Since we didn't set `out_dir`, all such added flags were simply ignored. Normally, it reads `OUT_DIR`, which is fine if `cc-rs` is used within a build script. But if it is used elsewhere, then this is a pretty gnarly footgun in `cc-rs`, because the failure is [completely silent](https://github.com/rust-lang/cc-rs/blob/main/src/lib.rs#L1483). CC @madsmtm or @NobodyXu in case you have thoughts on that :) r? @bjorn3

rust-bors · 2026-06-20T10:49:00Z

💔 Test for b946733 failed: CI. Failed job:

auto - x86_64-gnu-distcheck (web logs, enhanced plaintext logs)

Kobzol · 2026-06-20T10:55:16Z

@bors try jobs=x86_64-gnu-distcheck

Fix cc rs flag if supported try-job: x86_64-gnu-distcheck

NobodyXu · 2026-06-20T12:55:05Z

Thanks, I've opened an issue #1765, I think this is something we should fix.

We could use a tempfile instead for it

ChrisDenton · 2026-06-20T13:08:30Z

Thanks, I've opened an issue #1765

I think you meant rust-lang/cc-rs#1765 😉

rust-bors · 2026-06-20T13:18:25Z

☀️ Try build successful (CI)
Build commit: d269546 (d269546b8320f5f3255b5c7e6268def1a4808374)
Base parent: 4008bbd (4008bbdf34b583ce44a467043aae3703afc0a76f)

Kobzol · 2026-06-20T13:28:07Z

@bors r=bjorn3

Let's try again.

rust-bors · 2026-06-20T13:28:10Z

📌 Commit d59253e has been approved by bjorn3

It is now in the queue for this repository.

Fix debuginfo compression in bootstrap try-job: dist-x86_64-msvc try-job: dist-x86_64-apple try-job: dist-x86_64-linux

rust-bors · 2026-06-30T23:39:56Z

💥 Test timed out after 21600s

Kobzol · 2026-07-01T06:00:02Z

The Apple timeout looks spurious.

I enabled the compression only on Linux-like OSes, for now.

@rustbot ready

bjorn3 · 2026-07-01T08:37:21Z

@bors r+

rust-bors · 2026-07-01T08:37:24Z

📌 Commit 9f7569b has been approved by bjorn3

It is now in the queue for this repository.

@madsmtm

…, r=bjorn3 Fix debuginfo compression in bootstrap Found through https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/weird.20code.20in.20fill_target_compiler/with/604588655. This PR solves a few issues with debuginfo compression in bootstrap. The main issue was that debuginfo compression through the `-gz` flag wasn't enabled, by mistake. When `cc-rs` checks if a compiler flag is supported, it tries to read `out_dir` to generate the source file in. However, when this option is not set, then the check silently fails and the flag is considered to be unsupported. Since we didn't set `out_dir`, all such added flags were simply ignored. Normally, it reads `OUT_DIR`, which is fine if `cc-rs` is used within a build script. But if it is used elsewhere, then this is a pretty gnarly footgun in `cc-rs`, because the failure is [completely silent](https://github.com/rust-lang/cc-rs/blob/main/src/lib.rs#L1483). CC @madsmtm or @NobodyXu in case you have thoughts on that :) After that was fixed, I had to change the used compression flag from `-gz` to `--compress-debug-sections`, to support both BFD and LLD linkers. And to solve it properly, and allow `dist` CI jobs to configure debuginfo compression for all targets that they build, I added a new bootstrap option to configure debuginfo compression. I wanted the flag to be configurable both globally and per target. At the same time, the flag applies both to C/C++ and Rust. We currently don't have such config area in `bootstrap.toml`, and `[build]` didn't seem like the right place, so I shoved it into `[rust]` (while documenting that it also applies to C/C++). r? @bjorn3 try-job: dist-x86_64-msvc try-job: dist-x86_64-apple try-job: dist-x86_64-linux

…uwer Rollup of 5 pull requests Successful merges: - #158169 (Fix debuginfo compression in bootstrap) - #158613 (Fix getrandom fallback test on platforms with `panic=abort`) - #158620 (Remove skip_norm_w/i/p().def_id with a helper) - #158633 (Remove unnecessary `Clone` derives on resolver types) - #158634 (Add missing `needs_drop` check to `DroplessArena`.)

@madsmtm

…, r=bjorn3 Fix debuginfo compression in bootstrap Found through https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/weird.20code.20in.20fill_target_compiler/with/604588655. This PR solves a few issues with debuginfo compression in bootstrap. The main issue was that debuginfo compression through the `-gz` flag wasn't enabled, by mistake. When `cc-rs` checks if a compiler flag is supported, it tries to read `out_dir` to generate the source file in. However, when this option is not set, then the check silently fails and the flag is considered to be unsupported. Since we didn't set `out_dir`, all such added flags were simply ignored. Normally, it reads `OUT_DIR`, which is fine if `cc-rs` is used within a build script. But if it is used elsewhere, then this is a pretty gnarly footgun in `cc-rs`, because the failure is [completely silent](https://github.com/rust-lang/cc-rs/blob/main/src/lib.rs#L1483). CC @madsmtm or @NobodyXu in case you have thoughts on that :) After that was fixed, I had to change the used compression flag from `-gz` to `--compress-debug-sections`, to support both BFD and LLD linkers. And to solve it properly, and allow `dist` CI jobs to configure debuginfo compression for all targets that they build, I added a new bootstrap option to configure debuginfo compression. I wanted the flag to be configurable both globally and per target. At the same time, the flag applies both to C/C++ and Rust. We currently don't have such config area in `bootstrap.toml`, and `[build]` didn't seem like the right place, so I shoved it into `[rust]` (while documenting that it also applies to C/C++). r? @bjorn3 try-job: dist-x86_64-msvc try-job: dist-x86_64-apple try-job: dist-x86_64-linux

…uwer Rollup of 8 pull requests Successful merges: - #150075 (Implement clamp_to) - #158169 (Fix debuginfo compression in bootstrap) - #158397 (delegation: support simplest output `Self` mapping) - #158613 (Fix getrandom fallback test on platforms with `panic=abort`) - #158620 (Remove skip_norm_w/i/p().def_id with a helper) - #158633 (Remove unnecessary `Clone` derives on resolver types) - #158634 (Add missing `needs_drop` check to `DroplessArena`.) - #158647 (Document `strip_circumfix` behavior on overlapping prefix and suffix.)

JonathanBrouwer · 2026-07-01T14:18:35Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #158660 (comment)

rust-bors · 2026-07-01T14:18:42Z

This pull request was unapproved.

This PR was contained in a rollup (#158660), which was unapproved.

View changes since this unapproval

Kobzol · 2026-07-02T07:26:21Z

Hmm, dist-various-2 fails, because it links Fuchsia, which is using rust-lld linker directly, rather than going through cc. To setup compression with cc, I have to pass -Wl,--compress-debug-sections=zlib, but when using the linker directly, it should be just --compress-debug-sections=zlib, without the -Wl. I can special-case that in bootstrap, but I wonder if I'm missing some easier solution to this, it feels hacky. Or maybe I should only enable passing the flag on Linux and nowhere else...

@bjorn3 Any ideas? :)

bjorn3 · 2026-07-02T09:53:19Z

I guess only passing it on Linux for now and opening an issue for getting it to work on other targets is fine. We didn't compress debuginfo at all before this PR anyway, so it is not regressing anything.

Kobzol · 2026-07-03T05:14:10Z

@bors try

Fix debuginfo compression in bootstrap try-job: dist-x86_64-msvc try-job: dist-x86_64-apple try-job: dist-x86_64-linux try-job: dist-various-1 try-job: dist-various-2

rust-bors · 2026-07-03T08:52:40Z

☀️ Try build successful (CI)
Build commit: 217ff87 (217ff875d701cb36dbe8f2cc525b968e4d2bda9c)
Base parent: c397dae (c397dae808f70caebab1fc4e11b3edf7e59f58c7)

Kobzol · 2026-07-03T08:53:46Z

Ok, makes sense.

@rustbot ready

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Auto merge of #158169 - Kobzol:fix-cc-rs-flag-if-supported, r=<try>

d269546

Fix cc rs flag if supported try-job: x86_64-gnu-distcheck

NobodyXu mentioned this pull request Jun 20, 2026

Fix flag_if_supported when OUT_DIR not set rust-lang/cc-rs#1765

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Auto merge of #158169 - Kobzol:fix-cc-rs-flag-if-supported, r=<try>

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Fix debuginfo compression in bootstrap try-job: dist-x86_64-msvc try-job: dist-x86_64-apple try-job: dist-x86_64-linux

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JonathanBrouwer mentioned this pull request Jul 1, 2026

Rollup of 5 pull requests #158650

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Rollup of 8 pull requests #158660

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Pass -Wl based on whether we are using a host linker

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