[Buildroot] [PATCH] package/dtui: require 64-bit atomic support

* [Buildroot] [PATCH] package/dtui: require 64-bit atomic support
@ 2026-08-29 11:01 Christopher Obbard via buildroot
  2026-08-29 21:12 ` Thomas Petazzoni via buildroot
  0 siblings, 1 reply; 3+ messages in thread
From: Christopher Obbard via buildroot @ 2026-08-29 11:01 UTC (permalink / raw)
  To: buildroot; +Cc: Christopher Obbard, Christopher Obbard

dtui depends on tui-textarea which unconditionally imports AtomicU64 in
src/widget.rs to pack a viewport rectangle into a single atomic word:

  use std::sync::atomic::{AtomicU64, Ordering};
  pub struct Viewport(AtomicU64);

As there is no cfg(target_has_atomic) guard in tui-textarea, its
build fails on any target for which rustc does not provide 64-bit
atomics with:

  Compiling tui-textarea v0.7.0
  error[E0432]: unresolved import `std::sync::atomic::AtomicU64`
    --> .../dtui-3.0.0/VENDOR/tui-textarea/src/widget.rs:10:25
     |
  10 | use std::sync::atomic::{AtomicU64, Ordering};
     |                         ^^^^^^^^^ no `AtomicU64` in `sync::atomic`
     |
  help: a similar name exists in the module
     |
  10 - use std::sync::atomic::{AtomicU64, Ordering};
  10 + use std::sync::atomic::{AtomicU32, Ordering};

This has been reported to tui-textarea upstream, but unfortunately the
project seems to be unmaintained (issue linked below). A sane workaround
is to disable the package on targets which lack 64-bit atomic support.

Of all the rust targets buildroot can generate (see RUST_TARGETS in
utils/update-rust), three lack 64-bit atomic support:

  $ 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"

The armv6 and armv7 targets, for comparison, are fine:

    arm-unknown-linux-gnueabi         "16" "32" "64" "8" "ptr"
    armv7-unknown-linux-gnueabihf     "16" "32" "64" "8" "ptr"

The armv5te targets come from BR2_ARM_CPU_ARMV5 and the powerpc target
from BR2_powerpc, which is 32-bit only. Disable the package for both.

The uclibc variants of these architectures are already excluded as
BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS only covers armv5te and
32-bit powerpc for glibc and musl.

Build tested with utils/test-pkg against:
- BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_ARMV5_EABI_GLIBC_STABLE
- BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_ARMV5_EABI_MUSL_STABLE
- BR2_TOOLCHAIN_EXTERNAL_BOOTLIN_POWERPC_E500MC_GLIBC_STABLE

all three fail with the above error before this change and are skipped
after it, while armv7 (glibc and musl), aarch64, powerpc64le and x86-64
still select and build the package.

The same problem was hit by package/dust and worked around in commit
3abc3b97bad9 ("package/dust: bump to version 1.1.2") by bumping to a
version in which upstream had added the missing guard. That is not an
option here as tui-textarea 0.7.0 is the latest release.

As a follow-up it could be worth adding a
BR2_PACKAGE_HOST_RUSTC_TARGET_HAS_ATOMIC_64 symbol to
package/rustc/Config.in.host, defaulting to y everywhere except the three
target combinations listed above. Packages could then express this
constraint as a single dependency and it would stay correct as rust
gains new targets.

Link: https://github.com/rhysd/tui-textarea/issues/66
Fixes: https://autobuild.buildroot.org/results/188f6442371500731453f75983590c922eab6d57
Fixes: https://autobuild.buildroot.org/results/e254db2654f18f1d2110eb8b1a32b43ad0f2a3d6
Signed-off-by: Christopher Obbard <chris.obbard@oss.qualcomm.com>
---
 package/dtui/Config.in | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/package/dtui/Config.in b/package/dtui/Config.in
index 65d51df7d5..31e337a5e0 100644
--- a/package/dtui/Config.in
+++ b/package/dtui/Config.in
@@ -3,6 +3,10 @@ config BR2_PACKAGE_DTUI
 	depends on BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS
 	depends on BR2_TOOLCHAIN_HAS_THREADS # dbus
 	depends on BR2_USE_MMU # dbus
+	# tui-textarea unconditionally uses AtomicU64, which rustc does
+	# not provide on armv5te or 32-bit powerpc.
+	depends on !BR2_ARM_CPU_ARMV5
+	depends on !BR2_powerpc
 	select BR2_PACKAGE_DBUS # runtime
 	select BR2_PACKAGE_HOST_RUSTC
 	help

---
base-commit: e991fa071605a78c17adba2ed26e07c3b8c95583
change-id: 20260822-wip-obbardc-package-dtui-fix-armv5-832655f4860b

Best regards,
--  
Christopher Obbard <chris.obbard@oss.qualcomm.com>

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