Provide fallback for rustc version when envvars not present.

Fixes an issue where `CROSS_RUSTC_MINOR_VERSION` is not present when
using older versions of cross but newer images. This only uses the
fallback if the minor version is not provided as an environment variable
by cross itself.

Author: Alexhuszagh

docker/Dockerfile.aarch64-unknown-linux-musl

@@ -21,6 +21,7 @@ COPY musl-symlink.sh /
 RUN /musl-symlink.sh $CROSS_MUSL_SYSROOT aarch64
 
 COPY aarch64-linux-musl-gcc.sh /usr/bin/
+COPY rustc_info.sh /
 
 COPY qemu-runner base-runner.sh /
 

docker/Dockerfile.armv5te-unknown-linux-musleabi

@@ -27,6 +27,7 @@ RUN /musl-symlink.sh $CROSS_MUSL_SYSROOT arm
 COPY qemu-runner base-runner.sh /
 
 COPY arm-linux-musleabi-gcc.sh /usr/bin/
+COPY rustc_info.sh /
 
 ENV CARGO_TARGET_ARMV5TE_UNKNOWN_LINUX_MUSLEABI_LINKER=arm-linux-musleabi-gcc.sh \
     CARGO_TARGET_ARMV5TE_UNKNOWN_LINUX_MUSLEABI_RUNNER="/qemu-runner arm" \

docker/Dockerfile.mips64-unknown-linux-muslabi64

@@ -28,6 +28,7 @@ RUN ln -s $CROSS_MUSL_SYSROOT/usr/lib/libc.so $CROSS_MUSL_SYSROOT/usr/lib64/libc
 RUN ln -s $CROSS_MUSL_SYSROOT/usr/lib/libc.so.1 $CROSS_MUSL_SYSROOT/usr/lib64/libc.so.1
 
 COPY mips64-linux-musl-gcc.sh /usr/bin/
+COPY rustc_info.sh /
 
 COPY qemu-runner base-runner.sh /
 

docker/Dockerfile.mips64el-unknown-linux-muslabi64

@@ -28,6 +28,7 @@ RUN ln -s $CROSS_MUSL_SYSROOT/usr/lib/libc.so $CROSS_MUSL_SYSROOT/usr/lib64/libc
 RUN ln -s $CROSS_MUSL_SYSROOT/usr/lib/libc.so.1 $CROSS_MUSL_SYSROOT/usr/lib64/libc.so.1
 
 COPY mips64el-linux-musl-gcc.sh /usr/bin/
+COPY rustc_info.sh /
 
 COPY qemu-runner base-runner.sh /
 

docker/aarch64-linux-musl-gcc.sh

@@ -7,8 +7,14 @@
 set -x
 set -euo pipefail
 
+# shellcheck disable=SC1091
+. /rustc_info.sh
+
 main() {
-    if (( CROSS_RUSTC_MINOR_VERSION >= 48 )) || [[ $# -eq 0 ]]; then
+    local minor
+    minor=$(rustc_minor_version)
+
+    if (( minor >= 48 )) || [[ $# -eq 0 ]]; then
         # no workaround
         exec aarch64-linux-musl-gcc "${@}"
     else

docker/arm-linux-musleabi-gcc.sh

@@ -9,8 +9,14 @@
 set -x
 set -euo pipefail
 
+# shellcheck disable=SC1091
+. /rustc_info.sh
+
 main() {
-    if (( CROSS_RUSTC_MINOR_VERSION >= 65 )) || [[ $# -eq 0 ]]; then
+    local minor
+    minor=$(rustc_minor_version)
+
+    if (( minor >= 65 )) || [[ $# -eq 0 ]]; then
         exec arm-linux-musleabi-gcc "${@}"
     else
         exec arm-linux-musleabi-gcc "${@}" -lgcc -static-libgcc

docker/mips64-linux-musl-gcc.sh

@@ -9,8 +9,14 @@
 set -x
 set -euo pipefail
 
+# shellcheck disable=SC1091
+. /rustc_info.sh
+
 main() {
-    if (( CROSS_RUSTC_MINOR_VERSION >= 65 )) || [[ $# -eq 0 ]]; then
+    local minor
+    minor=$(rustc_minor_version)
+
+    if (( minor >= 65 )) || [[ $# -eq 0 ]]; then
         exec mips64-linux-musl-gcc "${@}"
     else
         exec mips64-linux-musl-gcc "${@}" -lgcc -static-libgcc

docker/mips64el-linux-musl-gcc.sh

@@ -9,8 +9,14 @@
 set -x
 set -euo pipefail
 
+# shellcheck disable=SC1091
+. /rustc_info.sh
+
 main() {
-    if (( CROSS_RUSTC_MINOR_VERSION >= 65 )) || [[ $# -eq 0 ]]; then
+    local minor
+    minor=$(rustc_minor_version)
+
+    if (( minor >= 65 )) || [[ $# -eq 0 ]]; then
         exec mips64el-linux-musl-gcc "${@}"
     else
         exec mips64el-linux-musl-gcc "${@}" -lgcc -static-libgcc

docker/rustc_info.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+# FIXME: remove this file further on, especially after
+# 0.2.5 has been released and we've had a weeks of
+# releases on main so people can update images.
+# people may use newer versions of cross with older
+# images for backwards compatibility, but we don't
+# need to guarantee newer images work with older cross
+# versions.
+# https://github.com/cross-rs/cross/issues/1046
+
+# NOTE: this will fail if rustc does not provide version
+# info, which may happen with a custom toolchain.
+rustc_version() {
+    rustc -Vv | grep '^release:' | cut -d ':' -f2
+}
+
+rustc_major_version() {
+    if [[ -z "${CROSS_RUSTC_MAJOR_VERSION:-}" ]]; then
+        CROSS_RUSTC_MAJOR_VERSION=$(rustc_version | cut -d '.' -f1)
+        export CROSS_RUSTC_MAJOR_VERSION
+    fi
+    echo "${CROSS_RUSTC_MAJOR_VERSION}"
+}
+
+rustc_minor_version() {
+    if [[ -z "${CROSS_RUSTC_MINOR_VERSION:-}" ]]; then
+        CROSS_RUSTC_MINOR_VERSION=$(rustc_version | cut -d '.' -f2)
+        export CROSS_RUSTC_MINOR_VERSION
+    fi
+    echo "${CROSS_RUSTC_MINOR_VERSION}"
+}
+
+rustc_patch_version() {
+    if [[ -z "${CROSS_RUSTC_PATCH_VERSION:-}" ]]; then
+        CROSS_RUSTC_PATCH_VERSION=$(rustc_version | cut -d '.' -f3)
+        export CROSS_RUSTC_PATCH_VERSION
+    fi
+    echo "${CROSS_RUSTC_PATCH_VERSION}"
+}