[RFC] remove build dependency on arm-none-eabi-gcc (binary blob alternative)

.gitignore

@@ -1,3 +1,6 @@
 **/*.rs.bk
 Cargo.lock
+bin/*.after
+bin/*.before
+bin/*.o
 target/

.travis.yml

@@ -3,40 +3,25 @@ language: rust
 matrix:
   include:
     - env: TARGET=x86_64-unknown-linux-gnu
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
-    - env: TARGET=thumbv6m-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv6m-none-eabi CC=clang
+    - env: TARGET=thumbv6m-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
     - env: TARGET=thumbv7m-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv7m-none-eabi CC=clang
-      rust: stable
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
     - env: TARGET=thumbv7em-none-eabi
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv7em-none-eabi CC=clang
-      rust: stable
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
     - env: TARGET=thumbv7em-none-eabihf
       rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
-    - env: TARGET=thumbv7em-none-eabihf CC=clang
-      rust: stable
-      if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
-
     - env: TARGET=thumbv6m-none-eabi
       rust: nightly
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)

Cargo.toml

@@ -9,9 +9,6 @@ name = "cortex-m-rt"
 repository = "https://github.com/japaric/cortex-m-rt"
 version = "0.5.2"
 
-[build-dependencies]
-cc = "1.0.10"
-
 [dependencies]
 r0 = "0.2.1"
 

asm.s

@@ -1,3 +1,4 @@
+  .section .text.HardFault
   .global HardFault
   .thumb_func
 HardFault:

assemble.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+# cflags taken from cc 1.0.22
+
+crate=cortex-m-rt
+
+arm-none-eabi-as -march=armv6s-m asm.s -o bin/$crate.o
+ar crs bin/thumbv6m-none-eabi.a bin/$crate.o
+
+arm-none-eabi-as -march=armv7-m asm.s -o bin/$crate.o
+ar crs bin/thumbv7m-none-eabi.a bin/$crate.o
+
+arm-none-eabi-as -march=armv7e-m asm.s -o bin/$crate.o
+ar crs bin/thumbv7em-none-eabi.a bin/$crate.o
+ar crs bin/thumbv7em-none-eabihf.a bin/$crate.o
+
+rm bin/$crate.o

build.rs

@@ -1,18 +1,21 @@
-extern crate cc;
-
 use std::env;
-use std::fs::File;
+use std::fs::{self, File};
 use std::io::Write;
 use std::path::PathBuf;
 
 fn main() {
     let target = env::var("TARGET").unwrap();
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
 
     has_fpu(&target);
     let is_armv6m = is_armv6m(&target);
 
     if target.starts_with("thumbv") {
-        cc::Build::new().file("asm.s").compile("asm");
+        fs::copy(
+            format!("bin/{}.a", target),
+            out_dir.join("libcortex-m-rt.a"),
+        ).unwrap();
+        println!("cargo:rustc-link-lib=static=cortex-m-rt");
     }
 
     // Put the linker script somewhere the linker can find it

check-blobs.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+# Checks that the blobs are up to date with the committed assembly files
+
+set -euxo pipefail
+
+for lib in $(ls bin/*.a); do
+    filename=$(basename $lib)
+    arm-none-eabi-objdump -Cd $lib > bin/${filename%.a}.before
+done
+
+./assemble.sh
+
+for lib in $(ls bin/*.a); do
+    filename=$(basename $lib)
+    arm-none-eabi-objdump -Cd $lib > bin/${filename%.a}.after
+done
+
+for cksum in $(ls bin/*.after); do
+    diff -u $cksum ${cksum%.after}.before
+done

ci/install.sh

@@ -3,13 +3,11 @@ set -euxo pipefail
 main() {
     if [ $TARGET != x86_64-unknown-linux-gnu ]; then
         rustup target add $TARGET
+    fi
 
-        if [ ${CC:-gcc} = gcc ]; then
-            mkdir gcc
+    mkdir gcc
 
-            curl -L https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2?revision=bc2c96c0-14b5-4bb4-9f18-bceb4050fee7?product=GNU%20Arm%20Embedded%20Toolchain,64-bit,,Linux,7-2018-q2-update | tar --strip-components=1 -C gcc -xj
-        fi
-    fi
+    curl -L https://developer.arm.com/-/media/Files/downloads/gnu-rm/7-2018q2/gcc-arm-none-eabi-7-2018-q2-update-linux.tar.bz2?revision=bc2c96c0-14b5-4bb4-9f18-bceb4050fee7?product=GNU%20Arm%20Embedded%20Toolchain,64-bit,,Linux,7-2018-q2-update | tar --strip-components=1 -C gcc -xj
 }
 
 main

ci/script.sh

@@ -20,65 +20,63 @@ main() {
         # linking with GNU LD
         for ex in "${examples[@]}"; do
             cargo rustc --target $TARGET --example $ex -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
 
             cargo rustc --target $TARGET --example $ex --release -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
         done
         for ex in "${fail_examples[@]}"; do
             ! cargo rustc --target $TARGET --example $ex -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
 
             ! cargo rustc --target $TARGET --example $ex --release -- \
-                  -C link-arg=-nostartfiles \
-                  -C link-arg=-Wl,-Tlink.x
+                  -C linker=arm-none-eabi-ld \
+                  -C link-arg=-Tlink.x
         done
 
         cargo rustc --target $TARGET --example device --features device -- \
-              -C link-arg=-nostartfiles \
-              -C link-arg=-Wl,-Tlink.x
+              -C linker=arm-none-eabi-ld \
+              -C link-arg=-Tlink.x
 
         cargo rustc --target $TARGET --example device --features device --release -- \
-              -C link-arg=-nostartfiles \
-              -C link-arg=-Wl,-Tlink.x
+              -C linker=arm-none-eabi-ld \
+              -C link-arg=-Tlink.x
 
         # linking with rustc's LLD
         for ex in "${examples[@]}"; do
             cargo rustc --target $TARGET --example $ex -- \
                   -C linker=rust-lld \
-                  -Z linker-flavor=ld.lld \
                   -C link-arg=-Tlink.x
 
             cargo rustc --target $TARGET --example $ex --release -- \
                   -C linker=rust-lld \
-                  -Z linker-flavor=ld.lld \
                   -C link-arg=-Tlink.x
         done
         for ex in "${fail_examples[@]}"; do
             ! cargo rustc --target $TARGET --example $ex -- \
                   -C linker=rust-lld \
-                  -Z linker-flavor=ld.lld \
                   -C link-arg=-Tlink.x
 
             ! cargo rustc --target $TARGET --example $ex --release -- \
                   -C linker=rust-lld \
-                  -Z linker-flavor=ld.lld \
                   -C link-arg=-Tlink.x
         done
 
         cargo rustc --target $TARGET --example device --features device -- \
               -C linker=rust-lld \
-              -Z linker-flavor=ld.lld \
               -C link-arg=-Tlink.x
 
         cargo rustc --target $TARGET --example device --features device --release -- \
               -C linker=rust-lld \
-              -Z linker-flavor=ld.lld \
               -C link-arg=-Tlink.x
     fi
+
+    if [ $TARGET = x86_64-unknown-linux-gnu ]; then
+        ./check-blobs.sh
+    fi
 }
 
 main