librsvg: rustc 1.54.0 build fails on ARM64 (Linux and macOS)

[lovell]

rustc 1.53.0 works but 1.54.0 fails; needs investigating.

macOS

stable-x86_64-apple-darwin installed - rustc 1.54.0 (a178d0322 2021-07-26)

libtool:   error: object name conflicts in archive: .libs/librsvg-2.lax/librsvg_c_api.a//Users/runner/work/sharp-libvips/sharp-libvips/deps/svg/./.libs/librsvg_c_api.a

Linux glibc

stable-x86_64-unknown-linux-gnu installed - rustc 1.54.0 (a178d0322 2021-07-26)

libtool:   error: object name conflicts in archive: .libs/librsvg-2.lax/librsvg_c_api.a//deps/svg/./.libs/librsvg_c_api.a

Interestingly, Linux musl ARM64 works and that uses rustc nightly so I guess whatever causes this might already be fixed there.

[kleisauke]

It looks like this is the same issue as the one mentioned in #73 (comment). I think it's due to commit rust-lang/compiler-builtins@96bc62e which causes fp_mode.o to also conflict for non-musl ARM64 targets.

This can be resolved by rebuilding Rust's standard library using the build-std feature, similar as the musl ARM64 target (see e.g. commit 9f54bfd). Unfortunately, this requires a nightly version of Rust.

Perhaps there's a better way to resolve this?

[lovell]

I was kind of hoping this might be a new problem 😅

Switching to nightly rustc everywhere is probably the best approach right now, plus might unlock useful new features e.g. panic_immediate_abort can reduce binary size.

[kleisauke]

I think it's due to commit rust-lang/compiler-builtins@96bc62e which causes fp_mode.o to also conflict for non-musl ARM64 targets.

This assumption was incorrect, the fp_mode.o duplicate is actually resolved with that commit. The -Zbuild-std feature is no longer needed once PR rust-lang/compiler-builtins#444 is merged and this crate is updated in Rust. I guess it may take some time before it becomes available in a stable version.

The reason why the -Zbuild-std feature actually resolved this build error is that the c feature of the compiler-builtins crate is then implicitly skipped, this means that it doesn't leverage LLVM's optimized implementations (available in compiler-rt). Work-in-progress commit kleisauke@1a3f69d enables this feature, and currently fails for ARM64 in CI (as expected).

[kleisauke]

PR #123 removes this -Zbuild-std feature flag.