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Rust does not provide 64-bit atomics on every target Buildroot can
generate. rustc sets max_atomic_width = 32 for three of the 25 targets
listed in RUST_TARGETS in utils/update-rust, so
core::sync::atomic::AtomicU64 and AtomicI64 simply do not exist there:
$ rustc --print cfg --target <target> | grep target_has_atomic
armv5te-unknown-linux-gnueabi "16" "32" "8" "ptr"
armv5te-unknown-linux-musleabi "16" "32" "8" "ptr"
powerpc-unknown-linux-gnu "16" "32" "8" "ptr"
Every other supported target, including armv6, armv7, aarch64, all the
x86 variants, riscv64, s390x, sparc64 and both 64-bit powerpcs, has
them, e.g.:
arm-unknown-linux-gnueabi "16" "32" "64" "8" "ptr"
armv7-unknown-linux-gnueabihf "16" "32" "64" "8" "ptr"
A crate that uses 64-bit atomics without a cfg(target_has_atomic = "64")
guard therefore fails to build on those three targets with:
error[E0432]: unresolved import `std::sync::atomic::AtomicU64`
|
| atomic::{AtomicU64, AtomicU8, AtomicUsize, Ordering},
| ^^^^^^^^^ no `AtomicU64` in `sync::atomic`
This has been hit at least twice already: by package/dust, worked around
in commit 3abc3b97ba ("package/dust: bump to version 1.1.2") by moving
to a release in which upstream had added the guard and by package/dtui,
which has no such release available and had to open-code the affected
architectures instead.
It is likely to keep recurring: infra.basetest.BASIC_TOOLCHAIN_CONFIG
builds with BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_ARMV5_EABI_GLIBC_STABLE, so
every runtime test that does not override the toolchain compiles for
armv5te, one of the three affected targets. That is exactly how the two
failures above were found.
Add a hidden symbol so packages can express this constraint once, rather
than each open-coding BR2_ARM_CPU_ARMV5 and BR2_powerpc and needing to
update whenever rust gains or changes a target.
Note that armv5te and 32-bit powerpc are only supported by rust for
glibc and musl, so the uclibc variants of those architectures are
already excluded by BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS.
Signed-off-by: Christopher Obbard <chris.obbard@oss.qualcomm.com>
Reviewed-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at https://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on OFTC IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches