[wrapper] Make cc_wrapper.sh POSIX-compliant and use #!/bin/sh

toolchain/BUILD.toolchain.tpl

@@ -35,6 +35,7 @@ filegroup(
     name = "internal-use-wrapped-tools",
     srcs = [
         "%{wrapper_bin_prefix}cc_wrapper.sh",
+        "%{wrapper_bin_prefix}cc_wrapper_inner.sh",
     ],
     visibility = ["//visibility:private"],
 )

toolchain/cc_wrapper.sh.tpl

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 #
 # Copyright 2021 The Bazel Authors. All rights reserved.
 #
@@ -14,128 +14,23 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# shellcheck disable=SC1083
+SCRIPT_DIR=$(dirname "$0")
 
-set -euo pipefail
+# Search for `bash` on the system, and then execute cc_wrapper_inner.sh with
+# it.
 
-CLEANUP_FILES=()
+# Attempt #1: /bin/bash -- present on FHS-compliant systems, but notably absent
+# on others, including NixOS.
+test -e /bin/bash && exec /bin/bash "${SCRIPT_DIR}"/cc_wrapper_inner.sh "$@"
 
-function cleanup() {
-  if [[ ${#CLEANUP_FILES[@]} -gt 0 ]]; then
-    rm -f "${CLEANUP_FILES[@]}"
-  fi
-}
+# Attempt #2: /usr/bin/env bash -- /usr/bin/env is required by POSIX, but some
+# callers to the LLVM toolchain, such as rules_rust, clear $PATH and leave
+# nothing for /usr/bin/env to search for.
+test -e /usr/bin/env && test /usr/bin/env bash true &&
+  exec /usr/bin/env bash "${SCRIPT_DIR}"/cc_wrapper_inner.sh "$@"
 
-trap cleanup EXIT
+# Attempt #3: Try `command -v`.
+command -v bash && exec $(command -v bash) "${SCRIPT_DIR}"/cc_wrapper_inner.sh "$@"
 
-# See note in toolchain/internal/configure.bzl where we define
-# `wrapper_bin_prefix` for why this wrapper is needed.
-
-# this script is located at either
-# - <execroot>/external/<repo_name>/bin/cc_wrapper.sh
-# - <runfiles>/<repo_name>/bin/cc_wrapper.sh
-# The clang is located at
-# - <execroot>/external/<repo_name2>/bin/clang
-# - <runfiles>/<repo_name2>/bin/clang
-#
-# In both cases, getting to clang can be done via
-# Finding the current dir of this script,
-# - <execroot>/external/<repo_name>/bin/
-# - <runfiles>/<repo_name>/bin/
-# going back 2 directories
-# - <execroot>/external
-# - <runfiles>
-#
-# Going into %{toolchain_path_prefix} without the `external/` prefix + `bin/clang`
-#
-
-dirname_shim() {
-  local path="$1"
-
-  # Remove trailing slashes
-  path="${path%/}"
-
-  # If there's no slash, return "."
-  if [[ "${path}" != */* ]]; then
-    echo "."
-    return
-  fi
-
-  # Remove the last component after the final slash
-  path="${path%/*}"
-
-  # If it becomes empty, it means root "/"
-  echo "${path:-/}"
-}
-
-script_dir=$(dirname_shim "${BASH_SOURCE[0]}")
-toolchain_path_prefix="%{toolchain_path_prefix}"
-
-# Sometimes this path may be an absolute path in which case we dont do anything because
-# This is using the host toolchain to build.
-if [[ ${toolchain_path_prefix} != /* ]]; then
-  toolchain_path_prefix="${script_dir}/../../${toolchain_path_prefix#external/}"
-fi
-
-if [[ ! -f ${toolchain_path_prefix}bin/clang ]]; then
-  echo >&2 "ERROR: could not find clang; PWD=\"${PWD}\"; PATH=\"${PATH}\"; toolchain_path_prefix=${toolchain_path_prefix}."
-  exit 5
-fi
-
-OUTPUT=
-
-function parse_option() {
-  local -r opt="$1"
-  if [[ "${OUTPUT}" = "1" ]]; then
-    OUTPUT=${opt}
-  elif [[ "${opt}" = "-o" ]]; then
-    # output is coming
-    OUTPUT=1
-  fi
-}
-
-function sanitize_option() {
-  local -r opt=$1
-  if [[ ${opt} == */cc_wrapper.sh ]]; then
-    printf "%s" "${toolchain_path_prefix}bin/clang"
-  elif [[ ${opt} =~ ^-fsanitize-(ignore|black)list=[^/] ]] && [[ ${script_dir} == /* ]]; then
-    # shellcheck disable=SC2206
-    parts=(${opt/=/ }) # Split flag name and value into array.
-    printf "%s" "${parts[0]}=${script_dir}/../../../${parts[1]}"
-  else
-    printf "%s" "${opt}"
-  fi
-}
-
-cmd=()
-for ((i = 0; i <= $#; i++)); do
-  if [[ ${!i} == @* && -r "${i:1}" ]]; then
-    # Create a new, sanitized file.
-    tmpfile=$(mktemp)
-    CLEANUP_FILES+=("${tmpfile}")
-    while IFS= read -r opt; do
-      opt="$(
-        set -e
-        sanitize_option "${opt}"
-      )"
-      parse_option "${opt}"
-      echo "${opt}" >>"${tmpfile}"
-    done <"${!i:1}"
-    cmd+=("@${tmpfile}")
-  else
-    opt="$(
-      set -e
-      sanitize_option "${!i}"
-    )"
-    parse_option "${opt}"
-    cmd+=("${opt}")
-  fi
-done
-
-# Call the C++ compiler.
-"${cmd[@]}"
-
-# Generate an empty file if header processing succeeded.
-if [[ "${OUTPUT}" == *.h.processed ]]; then
-  echo -n >"${OUTPUT}"
-fi
+echo >&2 'Failed to find bash at /bin/bash or in PATH.'
+exit 1

toolchain/cc_wrapper_inner.sh.tpl

@@ -0,0 +1,158 @@
+#!/bin/sh
+#
+# Copyright 2021 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# shellcheck disable=SC1083
+
+set -euo
+
+cleanup() {
+  while read -r f; do
+    rm -f "${f}"
+  done <"${CLEANUP_FILES}"
+}
+
+CLEANUP_FILES=""
+
+trap cleanup EXIT
+
+# See note in toolchain/internal/configure.bzl where we define
+# `wrapper_bin_prefix` for why this wrapper is needed.
+
+# this script is located at either
+# - <execroot>/external/<repo_name>/bin/cc_wrapper.sh
+# - <runfiles>/<repo_name>/bin/cc_wrapper.sh
+# The clang is located at
+# - <execroot>/external/<repo_name2>/bin/clang
+# - <runfiles>/<repo_name2>/bin/clang
+#
+# In both cases, getting to clang can be done via
+# Finding the current dir of this script,
+# - <execroot>/external/<repo_name>/bin/
+# - <runfiles>/<repo_name>/bin/
+# going back 2 directories
+# - <execroot>/external
+# - <runfiles>
+#
+# Going into %{toolchain_path_prefix} without the `external/` prefix + `bin/clang`
+#
+
+dirname_shim() {
+  path="$1"
+
+  # Remove trailing slashes
+  path="${path%/}"
+
+  # If there's no slash, return "."
+  if [ "${path}" != "*/*" ]; then
+    echo "."
+    return
+  fi
+
+  # Remove the last component after the final slash
+  path="${path%/*}"
+
+  # If it becomes empty, it means root "/"
+  echo "${path:-/}"
+}
+
+script_dir=$(dirname_shim "$0")
+toolchain_path_prefix="%{toolchain_path_prefix}"
+
+# Sometimes this path may be an absolute path in which case we dont do anything because
+# This is using the host toolchain to build.
+case "${toolchain_path_prefix}" in
+/*) ;;
+*) toolchain_path_prefix="${script_dir}/../../${toolchain_path_prefix#external/}" ;;
+esac
+
+if [ ! -f "${toolchain_path_prefix}bin/clang" ]; then
+  echo >&2 "ERROR: could not find clang; PWD=\"${PWD}\"; PATH=\"${PATH}\"; toolchain_path_prefix=${toolchain_path_prefix}."
+  exit 5
+fi
+
+OUTPUT=
+
+parse_option() {
+  po_opt="$1"
+  if [ "${OUTPUT}" = "1" ]; then
+    OUTPUT=${po_opt}
+  elif [ "${po_opt}" = "-o" ]; then
+    # output is coming
+    OUTPUT=1
+  fi
+}
+
+sanitize_option() {
+  so_opt="$1"
+  case ${so_opt} in
+  */cc_wrapper.sh) printf "%s" "${toolchain_path_prefix}bin/clang" ;;
+  *)
+    if eval "case ${so_opt} in -fsanitize-ignorelist=*|-fsanitize-blacklist=*) [ ${script_dir} == /* ] ;; esac"; then
+      # Split flag name and value.
+      #
+      # shellcheck disable=SC2206
+      part0=$(echo "${so_opt}" | cut -d '=' -f 1)
+      part1=$(echo "${so_opt}" | cut -d '=' -f 2)
+      printf "%s" "${part0}=${script_dir}/../../../${part1}"
+    else
+      printf "%s" "${so_opt}"
+    fi
+    ;;
+  esac
+}
+
+COUNT=$#
+i=0
+while [ "${i}" -le "${COUNT}" ]; do
+  temp=""
+  eval "temp=\${${i}}"
+  substr="${temp#?}"
+  if eval "case ${temp} in @*) [ -r \"{substr}\" ] ;; esac"; then
+    # Create a new, sanitized file.
+    tmpfile=$(mktemp)
+    # POSIX shell does not support arrays, so we write the cleanup files as an
+    # array-separated list. We do not need to worry about spaces in filenames,
+    # because `mktemp` cannot use them when using the default template.
+    CLEANUP_FILES="${CLEANUP_FILES} ${tmpfile}"
+    while IFS= read -r opt; do
+      opt="$(
+        set -e
+        sanitize_option "${opt}"
+      )"
+      parse_option "${opt}"
+      echo "${opt}" >>"${tmpfile}"
+    done <"${substr}"
+    cmd="${cmd} ${tmpfile}"
+  else
+    opt="$(
+      set -e
+      sanitize_option "${temp}"
+    )"
+    parse_option "${opt}"
+    # The items within $cmd also cannot contain spaces, because of how
+    # `sanitize_option` behaves.
+    cmd="${cmd} ${opt}"
+  fi
+  i=$((i + 1))
+done
+
+# Call the C++ compiler.
+eval \""${cmd}"\"
+
+# Generate an empty file if header processing succeeded.
+if [ "${OUTPUT}" = "*.h.processed" ]; then
+  true >"${OUTPUT}"
+fi

toolchain/internal/configure.bzl

@@ -228,6 +228,17 @@ def llvm_config_impl(rctx):
         },
     )
 
+    # Inner CC wrapper script (redirect used for shell compatibility on Linux
+    # platforms).
+    if os != "darwin":
+        rctx.template(
+            "bin/cc_wrapper_inner.sh",
+            rctx.attr._cc_wrapper_inner_sh_tpl,
+            {
+                "%{toolchain_path_prefix}": llvm_dist_path_prefix,
+            },
+        )
+
     if hasattr(rctx, "repo_metadata"):
         return rctx.repo_metadata(reproducible = True)
     else:

toolchain/internal/repo.bzl

@@ -322,6 +322,9 @@ llvm_config_attrs.update({
     "_cc_wrapper_sh_tpl": attr.label(
         default = "//toolchain:cc_wrapper.sh.tpl",
     ),
+    "_cc_wrapper_inner_sh_tpl": attr.label(
+        default = "//toolchain:cc_wrapper_inner.sh.tpl",
+    ),
 })
 
 def llvm_repo_impl(rctx):