use different shell utils file depending on the platform (#52)

tools/build_defs/framework.bzl

@@ -80,9 +80,8 @@ CC_EXTERNAL_RULE_ATTRIBUTES = {
     #
     # link to the shell utilities used by the shell script in cc_external_rule_impl.
     "_utils": attr.label(
-        default = Label("//tools/build_defs:utils.sh"),
+        default = "@foreign_cc_platform_utils//:shell_utils",
         allow_single_file = True,
-        executable = True,
         cfg = "target",
     ),
     # we need to declare this attribute to access cc_toolchain
@@ -165,7 +164,7 @@ def cc_external_rule_impl(ctx, attrs):
         "echo \"Building external library '{}'\"".format(lib_name),
         "export TMPDIR=$(mktemp -d)",
         "trap \"{ rm -rf $TMPDIR; }\" EXIT",
-        "export EXT_BUILD_DEPS=$(mktemp -d --tmpdir=$EXT_BUILD_ROOT)",
+        "export EXT_BUILD_DEPS=$(create_tmp_dir $EXT_BUILD_ROOT)",
         "\n".join(_copy_deps_and_tools(inputs)),
         "define_absolute_paths $EXT_BUILD_ROOT/bin $EXT_BUILD_ROOT/bin",
         "export INSTALLDIR=$EXT_BUILD_ROOT/" + outputs.installdir.path,

tools/build_defs/utils_osx.sh

@@ -123,3 +123,10 @@ function define_absolute_paths() {
 function replace_absolute_paths() {
   replace_in_files $1 $2 $REPLACE_VALUE
 }
+
+# create temp directory in specific directory
+# $1 directory where to create temp directory
+function create_tmp_dir() {
+  local in_folder=$1
+  mktemp -d -t ${in_folder}
+}

tools/build_defs/utils_unix.sh

@@ -0,0 +1,132 @@
+#!/usr/bin/env bash
+
+# default placeholder value
+REPLACE_VALUE='BAZEL_GEN_ROOT'
+
+# Echo variables in the format
+# var1_name="var1_value"
+# ...
+# vark_name="vark_value"
+#
+# arguments: the names of the variables
+function echo_vars() {
+  for arg in "$@"
+  do
+    echo_var "$arg"
+  done
+}
+
+# Echo variable in the format var_name="var_value"
+# $1 the name of the variable
+function echo_var() {
+  local name="$1"
+  local value=${!name}
+  echo "$name: \"${value}\""
+}
+
+# Wrap the function execution in the echo lines:
+# --- START $1
+# (anything printed by $2)
+# --- END $1
+# $1 parameter to be printed next to start/end text
+# $2 function to call in between START and END
+function wrap() {
+  echo "--- START $1:"
+  $2
+  echo "--- END $1"
+}
+
+# Append string to PATH variable
+# $1 string to append
+function path() {
+  export PATH="$1:$PATH"
+}
+
+# Replace string in all files in directory
+# $1 directory to search recursively, absolute path
+# $2 string to replace
+# $3 replace target
+function replace_in_files() {
+  if [ -d "$1" ]; then
+    find $1 -type f -exec sed -i 's@'"$2"'@'"$3"'@g' {} ';'
+  fi
+}
+
+# copies contents of the directory to target directory (create the target directory if needed)
+# $1 source directory, immediate children of which are copied
+# $2 target directory
+function copy_dir_contents_to_dir() {
+  local children=$(find $1 -maxdepth 1 -mindepth 1)
+  local target="$2"
+  mkdir -p ${target}
+  for child in $children; do
+    cp -R $child ${target}
+  done
+}
+
+# Symlink contents of the directory to target directory (create the target directory if needed).
+# If file is passed, symlink it into the target directory.
+# $1 source directory, immediate children of which are symlinked, or file to be symlinked.
+# $2 target directory
+function symlink_contents_to_dir() {
+  local target="$2"
+  mkdir -p ${target}
+  if [[ -f $1 ]]; then
+    symlink_to_dir $1 ${target}
+    return 0
+  fi
+  local children=$(find $1 -maxdepth 1 -mindepth 1)
+  for child in $children; do
+    symlink_to_dir $child ${target}
+  done
+}
+
+# Symlink all files from source directory to target directory (create the target directory if needed)
+# NB symlinks from the source directory are copied
+# $1 source directory
+# $2 target directory
+function symlink_to_dir() {
+  local target="$2"
+  mkdir -p ${target}
+
+  if [[ -d $1 ]]; then
+    ln -s -t ${target} $1
+  elif [[ -f $1 ]]; then
+    ln -s -t ${target} $1
+  elif [[ -L $1 ]]; then
+    cp $1 ${target}
+  else
+    echo "Can not copy $1"
+  fi
+}
+
+# Copy all files from source directory to target directory (create the target directory if needed),
+# and add target paths on to path
+# $1 source directory
+# $2 target directory
+function copy_and_add_to_path() {
+  copy_to_dir $1 $2
+  path $2/bin
+  path $2
+}
+
+# replace placeholder with absolute path in all files in a directory
+# $1 directory
+# $2 absolute path
+function define_absolute_paths() {
+  replace_in_files $1 $REPLACE_VALUE $2
+}
+
+# replace the absolute path with a placeholder value in all files in a directory
+# $1 directory
+# $2 absolute path to replace
+function replace_absolute_paths() {
+  replace_in_files $1 $2 $REPLACE_VALUE
+}
+
+# create temp directory in specific directory
+# $1 directory where to create temp directory
+function create_tmp_dir() {
+  local in_folder=$1
+  mktemp -d --tmpdir=${in_folder}
+}

workspace_definitions.bzl

@@ -1,5 +1,28 @@
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
+def _define_shell_utils_impl(rctx):
+    os_name = rctx.os.name.lower()
+    utils_name = "utils_unix.sh"
+    if os_name.startswith("mac os"):
+        utils_name = "utils_osx.sh"
+    if os_name.find("windows") != -1:
+        utils_name = "utils_win.bat"
+        fail("Not supported yet!")
+    rctx.file("WORKSPACE", "workspace(name='foreign_cc_platform_utils')")
+    rctx.file("BUILD.bazel", """
+sh_library(
+  name = "shell_utils",
+  srcs = ["{}"],
+  visibility = ["//visibility:public"]
+)
+""".format(utils_name))
+    path = rctx.path(Label("//tools/build_defs:" + utils_name))
+    rctx.template(utils_name, path, executable = True)
+
+_define_shell_utils = repository_rule(
+    implementation = _define_shell_utils_impl,
+)
+
 def rules_foreign_cc_dependencies():
     _all_content = """filegroup(name = "all", srcs = glob(["**"]), visibility = ["//visibility:public"])"""
 
@@ -13,3 +36,5 @@ def rules_foreign_cc_dependencies():
             "https://github.com/bazelbuild/bazel-skylib/archive/0.5.0.tar.gz",
         ],
     )
+
+    _define_shell_utils(name = "foreign_cc_platform_utils")