Custom toolchain fails if stdlib is not coupled to compiler

[RafaelMarinheiro]

I'm trying to create a custom toolchain in which the compiler and the stdlib are in separate repositories. I'm trying to do this to make bazel download only the pieces I want.

An example toolchain definition looks as follows (note that rust_lib comes from a different repo):

rust_toolchain(
    name = "rust-toolchain-x86_64-unknown-linux-gnu-to-x86_64-unknown-linux-gnu-impl",
    rust_doc = "@rustc_1.33.0_x86_64-unknown-linux-gnu//:rustdoc",
    rust_lib = "@rust_std_1.33.0_x86_64-unknown-linux-gnu//:rust_lib",
    rustc = "@rustc_1.33.0_x86_64-unknown-linux-gnu//:rustc",
    rustc_lib = "@rustc_1.33.0_x86_64-unknown-linux-gnu//:rustc_lib",
    staticlib_ext = ".a",
    dylib_ext = ".so",
    os = "linux",
    exec_triple = "x86_64-unknown-linux-gnu",
    target_triple = "x86_64-unknown-linux-gnu",
    visibility = ["//visibility:public"],
)

toolchain(
    name = "rust-toolchain-x86_64-unknown-linux-gnu-to-x86_64-unknown-linux-gnu",
    exec_compatible_with = ["@bazel_tools//platforms:linux", "@bazel_tools//platforms:x86_64"],
    target_compatible_with = ["@bazel_tools//platforms:linux", "@bazel_tools//platforms:x86_64"],
    toolchain = "rust-toolchain-x86_64-unknown-linux-gnu-to-x86_64-unknown-linux-gnu-impl",
    toolchain_type = "@io_bazel_rules_rust//rust:toolchain",
)

In this case both the compiler and the library are targeting the same platform. When I try to compile a hello world I get the following error:

$ bazel build -s //hello:hello
INFO: Analysed target //hello:hello (13 packages loaded, 230 targets configured).
INFO: Found 1 target...
SUBCOMMAND: # //hello:hello [action 'Compiling Rust bin hello (1 files)']
(cd /home/marinheiro/.cache/bazel/_bazel_marinheiro/d06419e7e664fd9ccf9c83b04640a470/execroot/testing && \
  exec env - \
    CARGO_PKG_AUTHORS='' \
    CARGO_PKG_DESCRIPTION='' \
    CARGO_PKG_HOMEPAGE='' \
    CARGO_PKG_NAME=hello \
    CARGO_PKG_VERSION=0.0.0 \
    CARGO_PKG_VERSION_MAJOR=0 \
    CARGO_PKG_VERSION_MINOR=0 \
    CARGO_PKG_VERSION_PATCH=0 \
    CARGO_PKG_VERSION_PRE='' \
  /bin/bash -c 'external/rustc_1.33.0_x86_64-unknown-linux-gnu/bin/rustc "$@" --remap-path-prefix="$(pwd)"=__bazel_redacted_pwd' '' hello/hello.rs '--crate-name=hello' '--crate-type=bin' '--codegen=metadata=' '--out-dir=bazel-out/k8-fastbuild/bin/hello' '--codegen=extra-filename=' '--codegen=opt-level=0' '--codegen=debuginfo=0' '--emit=dep-info,link' '--color=always' '--target=x86_64-unknown-linux-gnu' '--codegen=linker=/usr/bin/gcc' --codegen 'link-args=-fuse-ld=gold -Wl,-no-as-needed -Wl,-z,relro,-z,now -B/usr/bin -pass-exit-codes -lstdc++ -lm')
ERROR: /home/marinheiro/Code/embedded/hello/BUILD:6:1: error executing shell command: '/bin/bash -c external/rustc_1.33.0_x86_64-unknown-linux-gnu/bin/rustc "$@" --remap-path-prefix="$(pwd)"=__bazel_redacted_pwd  hello/hello.rs --crate-name=hello --crate-t
ype=bin --codegen=metadata= ...' failed (Exit 1) bash failed: error executing command /bin/bash -c 'external/rustc_1.33.0_x86_64-unknown-linux-gnu/bin/rustc "$@" --remap-path-prefix="$(pwd)"=__bazel_redacted_pwd' '' hello/hello.rs '--crate-name=hello' '--crate-type=bin' ... (remaining 11 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
error[E0463]: can't find crate for `std`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0463`.
Target //hello:hello failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.246s, Critical Path: 0.08s
INFO: 0 processes.
FAILED: Build did NOT complete successfull

From the output it looks like the generated command does not add the stdlib to the linker search path. Looking through the code it seems that it simply ignores that. Fixing it could be as simple as simply adding the -L flag to the generated command. I have not tried that yet, though.

[mfarrugi]

iirc rustc by default finds its shared libraries and the stdlib based on directory structure, don't know off hand how to change that. I think @acmcarther has come across this / it might be mentioned in an issue for cross compilation.

…

On Sun, Apr 7, 2019 at 11:54 PM Rafael Marinheiro ***@***.***> wrote: I'm trying to create a custom toolchain in which the compiler and the stdlib are in separate repositories. I'm trying to do this to make bazel download only the pieces I want. An example toolchain definition looks as follows (note that rust_lib comes from a different repo): rust_toolchain( name = "rust-toolchain-x86_64-unknown-linux-gnu-to-x86_64-unknown-linux-gnu-impl", rust_doc = ***@***.***_1.33.0_x86_64-unknown-linux-gnu//:rustdoc", rust_lib = ***@***.***_std_1.33.0_x86_64-unknown-linux-gnu//:rust_lib", rustc = ***@***.***_1.33.0_x86_64-unknown-linux-gnu//:rustc", rustc_lib = ***@***.***_1.33.0_x86_64-unknown-linux-gnu//:rustc_lib", staticlib_ext = ".a", dylib_ext = ".so", os = "linux", exec_triple = "x86_64-unknown-linux-gnu", target_triple = "x86_64-unknown-linux-gnu", visibility = ["//visibility:public"], ) toolchain( name = "rust-toolchain-x86_64-unknown-linux-gnu-to-x86_64-unknown-linux-gnu", exec_compatible_with = ***@***.***_tools//platforms:linux", ***@***.***_tools//platforms:x86_64"], target_compatible_with = ***@***.***_tools//platforms:linux", ***@***.***_tools//platforms:x86_64"], toolchain = "rust-toolchain-x86_64-unknown-linux-gnu-to-x86_64-unknown-linux-gnu-impl", toolchain_type = ***@***.***_bazel_rules_rust//rust:toolchain", ) In this case both the compiler and the library are targeting the same platform. When I try to compile a hello world I get the following error: $ bazel build -s //hello:hello INFO: Analysed target //hello:hello (13 packages loaded, 230 targets configured). INFO: Found 1 target... SUBCOMMAND: # //hello:hello [action 'Compiling Rust bin hello (1 files)'] (cd /home/marinheiro/.cache/bazel/_bazel_marinheiro/d06419e7e664fd9ccf9c83b04640a470/execroot/testing && \ exec env - \ CARGO_PKG_AUTHORS='' \ CARGO_PKG_DESCRIPTION='' \ CARGO_PKG_HOMEPAGE='' \ CARGO_PKG_NAME=hello \ CARGO_PKG_VERSION=0.0.0 \ CARGO_PKG_VERSION_MAJOR=0 \ CARGO_PKG_VERSION_MINOR=0 \ CARGO_PKG_VERSION_PATCH=0 \ CARGO_PKG_VERSION_PRE='' \ /bin/bash -c 'external/rustc_1.33.0_x86_64-unknown-linux-gnu/bin/rustc "$@" --remap-path-prefix="$(pwd)"=__bazel_redacted_pwd' '' hello/hello.rs '--crate-name=hello' '--crate-type=bin' '--codegen=metadata=' '--out-dir=bazel-out/k8-fastbuild/bin/hello' '--codegen=extra-filename=' '--codegen=opt-level=0' '--codegen=debuginfo=0' '--emit=dep-info,link' '--color=always' '--target=x86_64-unknown-linux-gnu' '--codegen=linker=/usr/bin/gcc' --codegen 'link-args=-fuse-ld=gold -Wl,-no-as-needed -Wl,-z,relro,-z,now -B/usr/bin -pass-exit-codes -lstdc++ -lm') ERROR: /home/marinheiro/Code/embedded/hello/BUILD:6:1: error executing shell command: '/bin/bash -c external/rustc_1.33.0_x86_64-unknown-linux-gnu/bin/rustc "$@" --remap-path-prefix="$(pwd)"=__bazel_redacted_pwd hello/hello.rs --crate-name=hello --crate-t ype=bin --codegen=metadata= ...' failed (Exit 1) bash failed: error executing command /bin/bash -c 'external/rustc_1.33.0_x86_64-unknown-linux-gnu/bin/rustc "$@" --remap-path-prefix="$(pwd)"=__bazel_redacted_pwd' '' hello/hello.rs '--crate-name=hello' '--crate-type=bin' ... (remaining 11 argument(s) skipped) Use --sandbox_debug to see verbose messages from the sandbox error[E0463]: can't find crate for `std` error: aborting due to previous error For more information about this error, try `rustc --explain E0463`. Target //hello:hello failed to build Use --verbose_failures to see the command lines of failed build steps. INFO: Elapsed time: 0.246s, Critical Path: 0.08s INFO: 0 processes. FAILED: Build did NOT complete successfull From the output it looks like the generated command does not add the stdlib to the linker search path. Looking through the code it seems that it simply ignores that. Fixing it could be as simple as simply adding the -L flag to the generated command. I have not tried that yet, though. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#213>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACLjeJYdtMACDKXY35ebGG00oda9tEXOks5ver1cgaJpZM4chPrd> .