remove build dependency on arm-none-eabi-gcc

by shipping pre-assembled object files. This is the same approach as the one
used in rust-embedded/cortex-m#95

Author: japaric

.gitignore

@@ -1,2 +1,6 @@
-target
+.#*
 Cargo.lock
+bin/*.after
+bin/*.before
+bin/*.o
+target

.travis.yml

@@ -3,22 +3,15 @@ language: rust
 matrix:
   include:
     - env: TARGET=x86_64-unknown-linux-gnu
+      rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
     - env: TARGET=thumbv6m-none-eabi
-      rust: beta
-      addons:
-        apt:
-          packages:
-            - gcc-arm-none-eabi
+      rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
     - env: TARGET=thumbv7m-none-eabi
-      rust: beta
-      addons:
-        apt:
-          packages:
-            - gcc-arm-none-eabi
+      rust: stable
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
     - env: TARGET=x86_64-unknown-linux-gnu
@@ -27,24 +20,17 @@ matrix:
 
     - env: TARGET=thumbv6m-none-eabi
       rust: nightly
-      addons:
-        apt:
-          packages:
-            - gcc-arm-none-eabi
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
     - env: TARGET=thumbv7m-none-eabi
       rust: nightly
-      addons:
-        apt:
-          packages:
-            - gcc-arm-none-eabi
       if: (branch = staging OR branch = trying) OR (type = pull_request AND branch = master)
 
 before_install: set -e
 
 install:
   - bash ci/install.sh
+  - export PATH="$PATH:$PWD/gcc/bin"
 
 script:
   - bash ci/script.sh

Cargo.toml

@@ -8,8 +8,5 @@ name = "cortex-m-semihosting"
 repository = "https://github.com/japaric/cortex-m-semihosting"
 version = "0.3.0"
 
-[build-dependencies]
-cc = "1.0.10"
-
 [features]
 inline-asm = []

asm.s

@@ -1,5 +1,6 @@
-.global __syscall
-
+  .section .text.__syscall
+  .global __syscall
+  .thumb_func
 __syscall:
   bkpt 0xAB
   bx lr

assemble.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+set -euxo pipefail
+
+# cflags taken from cc 1.0.22
+
+crate=cortex-m-semihosting
+
+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

bin/thumbv6m-none-eabi.a

@@ -1,13 +1,20 @@
-extern crate cc;
-
-use std::env;
+use std::path::PathBuf;
+use std::{env, fs};
 
 fn main() {
     let target = env::var("TARGET").unwrap();
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
+    let name = env::var("CARGO_PKG_NAME").unwrap();
 
     if target.starts_with("thumbv") {
         if env::var_os("CARGO_FEATURE_INLINE_ASM").is_none() {
-            cc::Build::new().file("asm.s").compile("asm");
+            fs::copy(
+                format!("bin/{}.a", target),
+                out_dir.join(format!("lib{}.a", name)),
+            ).unwrap();
+
+            println!("cargo:rustc-link-lib=static={}", name);
+            println!("cargo:rustc-link-search={}", out_dir.display());
         }
 
         println!("cargo:rustc-cfg=thumb");

bin/thumbv7em-none-eabi.a

@@ -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

bin/thumbv7em-none-eabihf.a

@@ -4,6 +4,10 @@ main() {
     if [ $TARGET != x86_64-unknown-linux-gnu ]; then
         rustup target add $TARGET
     fi
+
+    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
 }
 
 main

bin/thumbv7m-none-eabi.a

@@ -6,6 +6,10 @@ main() {
     if [ $TRAVIS_RUST_VERSION = nightly ]; then
         cargo check --target $TARGET --features inline-asm
     fi
+
+    if [ $TARGET = x86_64-unknown-linux-gnu ]; then
+        ./check-blobs.sh
+    fi
 }
 
 main