Error building dependencies with a custom `build.rs` script

[jdiez17]

Hi, I'm trying to build a Cargo workspace which depends on the ring crate. This crate has a custom build.rs script, and my Yocto build fails with the following output:

|   CC = Some(/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/wrappers/cc-wrapper.sh)                                     [7/1944]
|   RUSTC_WRAPPER = None
|   cargo:rerun-if-env-changed=CC_ENABLE_DEBUG_OUTPUT
|   cargo:rerun-if-env-changed=CRATE_CC_NO_DEFAULTS
|   CRATE_CC_NO_DEFAULTS = None
|   DEBUG = Some(true)
|   CARGO_CFG_TARGET_FEATURE = Some(fxsr,sse,sse2)
|   cargo:rerun-if-env-changed=CFLAGS
|   CFLAGS = Some( -O2 -pipe -g -feliminate-unused-debug-types -fcanon-prefix-map  -fmacro-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-
flight-software/git/git=/usr/src/debug/cybeesat-flight-software/git  -fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-softwar
e/git/git=/usr/src/debug/cybeesat-flight-software/git  -fmacro-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/target=/
usr/src/debug/cybeesat-flight-software/git  -fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/target=/usr/src/deb
ug/cybeesat-flight-software/git  -fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/recipe-sysroot=  -fmacro-prefi
x-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/recipe-sysroot=  -fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/co
rtexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/recipe-sysroot-native= )
|   cargo:rerun-if-env-changed=CC_SHELL_ESCAPED_FLAGS
|   CC_SHELL_ESCAPED_FLAGS = None
|   cargo:rerun-if-env-changed=HOST_CFLAGS
|   HOST_CFLAGS = Some()
|   cargo:rerun-if-env-changed=CFLAGS_x86_64_unknown_linux_gnu
|   CFLAGS_x86_64_unknown_linux_gnu = None
|   cargo:rerun-if-env-changed=CFLAGS_x86_64-unknown-linux-gnu
|   CFLAGS_x86_64-unknown-linux-gnu = None
|   CARGO_ENCODED_RUSTFLAGS = Some()
|   cargo:warning=arm-poky-linux-gnueabi-gcc: error: unrecognized command-line option '-m64'
|
|   --- stderr
|
|
|   error occurred in cc-rs: command did not execute successfully (status code exit status: 1): LC_ALL="C" "/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cyb
eesat-flight-software/git/wrappers/cc-wrapper.sh" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-4" "-fno-omit-frame-pointer" "-m64" "-I" "/home/builder/cybeesat/build/tmp/work
/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/cargo_home/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.14/include" "-I" "/home/builder/cybeesat/build/tmp/w
ork/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/cargo_home/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.14/pregenerated" "-fvisibility=hidden" "-std=c1x"
 "-Wall" "-Wbad-function-cast" "-Wcast-align" "-Wcast-qual" "-Wconversion" "-Wmissing-field-initializers" "-Wmissing-include-dirs" "-Wnested-externs" "-Wredundant-decls" "-Wshadow" "-Wsign-com
pare" "-Wsign-conversion" "-Wstrict-prototypes" "-Wundef" "-Wuninitialized" "-g3" "-DNDEBUG" "-O2" "-pipe" "-g" "-feliminate-unused-debug-types" "-fcanon-prefix-map" "-fmacro-prefix-map=/home/
builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/git=/usr/src/debug/cybeesat-flight-software/git" "-fdebug-prefix-map=/home/builder/cybee
sat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/git=/usr/src/debug/cybeesat-flight-software/git" "-fmacro-prefix-map=/home/builder/cybeesat/build/tmp
/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/target=/usr/src/debug/cybeesat-flight-software/git" "-fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/cort
exa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/target=/usr/src/debug/cybeesat-flight-software/git" "-fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-n
eon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/recipe-sysroot=" "-fmacro-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-
software/git/recipe-sysroot=" "-fdebug-prefix-map=/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/recipe-sysroot-native=" "-o" "/h
ome/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/target/release/build/ring-b223ecc4d5a766a0/out/25ac62e5b3c53843-curve25519.o" "-c" "
/home/builder/cybeesat/build/tmp/work/cortexa5t2hf-neon-vfpv4-poky-linux-gnueabi/cybeesat-flight-software/git/cargo_home/registry/src/index.crates.io-1949cf8c6b5b557f/ring-0.17.14/crypto/curve
25519/curve25519.c"

My recipe is very simple:

SUMMARY = "CyBEEsat Flight Software"
HOMEPAGE = "https://gitlab.com/rccn/missions/cybeesat/"
LICENSE = "GPL"

inherit cargo_bin

# Enable network for the compile task allowing cargo to download dependencies
do_compile[network] = "1"

SRC_URI = "gitsm://gitlab.com/rccn/missions/cybeesat.git;protocol=https;branch=main"
SRCREV="3db10d6228be6452fad99c0cd8c336d2e42331ee"
S = "${WORKDIR}/git"
LIC_FILES_CHKSUM = "file://LICENSE;md5=79409ca9a2f1e5e21d07bb10c0f5c7b7"

I'm not sure if this is a general problem when building build scripts (which are compiled for the host architecture), something specific to my setup, or something else entirely. Any help would be greatly appreciated. Thanks!

[CramBL]

The problem is not with build.rs in general, I have plenty of projects where I use it. Including to compile complicated C libraries like HDF5 for 32-bit arm (Zynq platform).

The problem is most likely with the ring support for 32-bit arm. If you don't need TLS you can disable the default features of tokio, or reqwest, or whatever you use, to avoid depending on these difficult to compile crypto libraries.

Alternatively you can try switching to native rust TLS. The easiest way is to not use TLS obviously. Look at which features that are available for the async crates you use, and try to find something that is easier to compile.