rust: Do not use default compiler flags defined in CC crate

Rust crates build dependecy C libraries using "CC" crate.
This crate adds some default compiler parameters depending on target arch.
For some targets these parameters conflict with the parameters defined by OE.

Warnings/errors like this can be seen in the case:

cc1: error: switch '-mcpu=cortex-a15' conflicts with switch '-march=armv7-a+fp' [-Werror]

Lets use only the OE parameters by exporting CRATE_CC_NO_DEFAULTS.
https://github.com/rust-lang/cc-rs#external-configuration-via-environment-variables

This patch fixes https://bugzilla.yoctoproject.org/show_bug.cgi?id=14947

Signed-off-by: Anton Antonov <Anton.Antonov@arm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 35 insertions, 9 deletions

diff --git a/meta/classes-recipe/rust-common.bbclass b/meta/classes-recipe/rust-common.bbclass
index 0f72e45e8c..e0cedd7aa2 100644
--- a/meta/classes-recipe/rust-common.bbclass
+++ b/meta/classes-recipe/rust-common.bbclass
@@ -97,7 +97,7 @@ RUST_BUILD_ARCH = "${@oe.rust.arch_to_rust_arch(d.getVar('BUILD_ARCH'))}"
 # Rust additionally will use two additional cases:
 # - undecorated (e.g. CC) - equivalent to TARGET
 # - triple suffix (e.g. CC:x86_64_unknown_linux_gnu) - both
-#   see: https://github.com/alexcrichton/gcc-rs
+#   see: https://github.com/rust-lang/cc-rs
 # The way that Rust's internal triples and Yocto triples are mapped together
 # its likely best to not use the triple suffix due to potential confusion.
 
@@ -128,12 +128,22 @@ create_wrapper_rust () {
 	shift
 	extras="$1"
 	shift
+	crate_cc_extras="$1"
+	shift
 
 	cat <<- EOF > "${file}"
 	#!/usr/bin/env python3
 	import os, sys
 	orig_binary = "$@"
 	extras = "${extras}"
+
+	# Apply a required subset of CC crate compiler flags
+	# when we build a target recipe for a non-bare-metal target.
+	# https://github.com/rust-lang/cc-rs/blob/main/src/lib.rs#L1614
+	if "CRATE_CC_NO_DEFAULTS" in os.environ.keys() and \
+	   "TARGET" in os.environ.keys() and not "-none-" in os.environ["TARGET"]:
+	    orig_binary += "${crate_cc_extras}"
+
 	binary = orig_binary.split()[0]
 	args = orig_binary.split() + sys.argv[1:]
 	if extras:
@@ -157,22 +167,22 @@ do_rust_create_wrappers () {
 	mkdir -p "${WRAPPER_DIR}"
 
 	# Yocto Build / Rust Host C compiler
-	create_wrapper_rust "${RUST_BUILD_CC}" "" "${BUILD_CC}"
+	create_wrapper_rust "${RUST_BUILD_CC}" "" "${CRATE_CC_FLAGS}" "${BUILD_CC}"
 	# Yocto Build / Rust Host C++ compiler
-	create_wrapper_rust "${RUST_BUILD_CXX}" "" "${BUILD_CXX}"
+	create_wrapper_rust "${RUST_BUILD_CXX}" "" "${CRATE_CC_FLAGS}" "${BUILD_CXX}"
 	# Yocto Build / Rust Host linker
-	create_wrapper_rust "${RUST_BUILD_CCLD}" "" "${BUILD_CCLD}" "${BUILD_LDFLAGS}"
+	create_wrapper_rust "${RUST_BUILD_CCLD}" "" "" "${BUILD_CCLD}" "${BUILD_LDFLAGS}"
 	# Yocto Build / Rust Host archiver
-	create_wrapper_rust "${RUST_BUILD_AR}" "" "${BUILD_AR}"
+	create_wrapper_rust "${RUST_BUILD_AR}" "" "" "${BUILD_AR}"
 
 	# Yocto Target / Rust Target C compiler
-	create_wrapper_rust "${RUST_TARGET_CC}" "${WRAPPER_TARGET_EXTRALD}" "${WRAPPER_TARGET_CC}" "${WRAPPER_TARGET_LDFLAGS}"
+	create_wrapper_rust "${RUST_TARGET_CC}" "${WRAPPER_TARGET_EXTRALD}" "${CRATE_CC_FLAGS}" "${WRAPPER_TARGET_CC}" "${WRAPPER_TARGET_LDFLAGS}"
 	# Yocto Target / Rust Target C++ compiler
-	create_wrapper_rust "${RUST_TARGET_CXX}" "${WRAPPER_TARGET_EXTRALD}" "${WRAPPER_TARGET_CXX}" "${CXXFLAGS}"
+	create_wrapper_rust "${RUST_TARGET_CXX}" "${WRAPPER_TARGET_EXTRALD}" "${CRATE_CC_FLAGS}" "${WRAPPER_TARGET_CXX}" "${CXXFLAGS}"
 	# Yocto Target / Rust Target linker
-	create_wrapper_rust "${RUST_TARGET_CCLD}" "${WRAPPER_TARGET_EXTRALD}" "${WRAPPER_TARGET_CCLD}" "${WRAPPER_TARGET_LDFLAGS}"
+	create_wrapper_rust "${RUST_TARGET_CCLD}" "${WRAPPER_TARGET_EXTRALD}" "" "${WRAPPER_TARGET_CCLD}" "${WRAPPER_TARGET_LDFLAGS}"
 	# Yocto Target / Rust Target archiver
-	create_wrapper_rust "${RUST_TARGET_AR}" "" "${WRAPPER_TARGET_AR}"
+	create_wrapper_rust "${RUST_TARGET_AR}" "" "" "${WRAPPER_TARGET_AR}"
 
 }
 
diff --git a/meta/classes-recipe/rust-target-config.bbclass b/meta/classes-recipe/rust-target-config.bbclass
index 7fd7128bcf..939dd13d2f 100644
--- a/meta/classes-recipe/rust-target-config.bbclass
+++ b/meta/classes-recipe/rust-target-config.bbclass
@@ -404,3 +404,19 @@ python do_rust_gen_targets () {
 addtask rust_gen_targets after do_patch before do_compile
 do_rust_gen_targets[dirs] += "${RUST_TARGETS_DIR}"
 
+# For building target C dependecies use only compiler parameters defined in OE
+# and ignore the CC crate defaults which conflicts with OE ones in some cases.
+# https://github.com/rust-lang/cc-rs#external-configuration-via-environment-variables
+# Some CC crate compiler flags are still required.
+# We apply them conditionally in rust wrappers.
+
+CRATE_CC_FLAGS:class-native = ""
+CRATE_CC_FLAGS:class-nativesdk = ""
+CRATE_CC_FLAGS:class-target = " -ffunction-sections -fdata-sections -fPIC"
+
+do_compile:prepend:class-target() {
+    export CRATE_CC_NO_DEFAULTS=1
+}
+do_install:prepend:class-target() {
+    export CRATE_CC_NO_DEFAULTS=1
+}