dist-i686-msvc fails with `STATUS_NO_MEMORY`

[mati865]

Creating this issue to have something to easily refer to. During bootstrap bump we got stuck on dist-i686-msvc job that keeps failing with exit code: 0xc0000017, STATUS_NO_MEMORY.

Click to see the possible cause of the failure (guessed by this bot)

LowFree:        12196008 kB
SwapTotal:       3014656 kB
SwapFree:        2860456 kB
##[endgroup]
Executing python x.py -j2 dist bootstrap --include-default-paths
+ python x.py -j2 dist bootstrap --include-default-paths
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 1.76s
##[endgroup]
downloading https://static.rust-lang.org/dist/2026-07-06/rustfmt-nightly-i686-pc-windows-msvc.tar.xz
extracting D:\a\rust\rust\build\cache\2026-07-06\rustfmt-nightly-i686-pc-windows-msvc.tar.xz to D:\a\rust\rust\build\i686-pc-windows-msvc\rustfmt
---
   Compiling quote v1.0.45
error: could not compile `quote` (build script)

Caused by:
  process didn't exit successfully: `sccache 'D:\a\rust\rust\build\bootstrap\debug\rustc' --crate-name build_script_build --edition=2021 'C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\quote-1.0.45\build.rs' --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off --cfg 'feature="default"' --cfg 'feature="proc-macro"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("default", "proc-macro"))' -C metadata=b72bb3a3a834151a --out-dir 'D:\a\rust\rust\build\i686-pc-windows-msvc\stage1-rustc\release\build\quote/03279c42beaf3f44\out' -L 'dependency=D:\a\rust\rust\build\i686-pc-windows-msvc\stage1-rustc\release\build\quote/03279c42beaf3f44\out' --cap-lints allow -Z binary-dep-depinfo` (exit code: 0xc0000017, STATUS_NO_MEMORY)
warning: build failed, waiting for other jobs to finish...
error: could not compile `proc-macro2` (build script)

Caused by:
  process didn't exit successfully: `sccache 'D:\a\rust\rust\build\bootstrap\debug\rustc' --crate-name build_script_build --edition=2021 'C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\proc-macro2-1.0.106\build.rs' --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off --cfg 'feature="default"' --cfg 'feature="proc-macro"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("default", "nightly", "proc-macro", "span-locations"))' -C metadata=0e3c0cd282f1e688 --out-dir 'D:\a\rust\rust\build\i686-pc-windows-msvc\stage1-rustc\release\build\proc-macro2/b3c4050290632628\out' -L 'dependency=D:\a\rust\rust\build\i686-pc-windows-msvc\stage1-rustc\release\build\proc-macro2/b3c4050290632628\out' --cap-lints allow -Z binary-dep-depinfo` (exit code: 0xc0000017, STATUS_NO_MEMORY)
Bootstrap failed while executing `-j2 dist bootstrap --include-default-paths`
Build completed unsuccessfully in 0:18:38
  local time: Fri Jul 10 02:51:27 CUT 2026
  network time: Fri, 10 Jul 2026 02:51:27 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"

Originally posted by @rust-log-analyzer in #158888 (comment)

[Mark-Simulacrum]

One thing I'm noticing is that the same job just built proc-macro2 during the bootstrap compilation. The failing build in the last attempt is a build script compilation:

process didn't exit successfully: sccache 'D:\a\rust\rust\build\bootstrap\debug\rustc' --crate-name build_script_build --edition=2021 'C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\proc-macro2-1.0.106\build.rs' --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debug-assertions=off --cfg 'feature="default"' --cfg 'feature="proc-macro"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("default", "nightly", "proc-macro", "span-locations"))' -C metadata=0e3c0cd282f1e688 --out-dir 'D:\a\rust\rust\build\i686-pc-windows-msvc\stage1-rustc\release\build\proc-macro2/b3c4050290632628\out' -L 'dependency=D:\a\rust\rust\build\i686-pc-windows-msvc\stage1-rustc\release\build\proc-macro2/b3c4050290632628\out' --cap-lints allow -Z binary-dep-depinfo (exit code: 0xc0000017, STATUS_NO_MEMORY)

so that same exact command should have already run, modulo sccache. Maybe the issue is with sccache? I'm going to try capturing the command from bootstrap build in the next try run, and then also try removing sccache and running a build with that.

[Mark-Simulacrum]

I think we are hitting rust-lang/cargo#17183. The PATH being setup by Cargo is ~44,740 characters, which exceeds the 32kb limit:

The ANSI version of this function, CreateProcessA fails if the total size of the environment block for the process exceeds 32,767 characters.

I'm not sure if the limit is the same for the Unicode version (or if we use the Unicode version), I don't see a limit described in the docs.

I think we'll either need to backport a fix like rust-lang/cargo#17191... cc @ranger-ross, how close are we on getting that PR in a reviewable/mergeable state?

I suspect we are hitting this after beta bump due to rust-lang/cargo#17164 (but haven't checked). That fixes other bugs (that I was hitting in #157590) so we definitely want to keep that IMO.

I guess another option on the Rust side is to revert using the new build dir layout.

@rust-lang/cargo, can you help steer here? I think our options are:

• Land Reduce library search path length in new build dir layout cargo#17191 and hope that fixes this (needs verification still, I think it needs to be on Windows so that's somewhat painful).
• Revert Enable Cargo's new build-dir layout #155439 on rust-lang/rust until new build dir is in a more polished state (dog-fooding is helpful to find this kind of thing ourselves but maybe the right answer for now to avoid a stream of beta backports)
• Some other option (open to suggestions)

(Taking this thread to an issue to avoid spamming everyone with bors try attempts)