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set -euo pipefail
# Assert that FILE exists and is executable
#
# assertExecutable FILE
assertExecutable() {
local file="$1"
[[ -f "$file" && -x "$file" ]] || \
die "Cannot wrap '$file' because it is not an executable file"
}
# Generate a binary executable wrapper for wrapping an executable.
# The binary is compiled from generated C-code using gcc.
# makeWrapper EXECUTABLE OUT_PATH ARGS
# ARGS:
# --argv0 NAME : set the name of the executed process to NAME
# (if unset or empty, defaults to EXECUTABLE)
# --inherit-argv0 : the executable inherits argv0 from the wrapper.
# (use instead of --argv0 '$0')
# --resolve-argv0 : if argv0 doesn't include a / character, resolve it against PATH
# --set VAR VAL : add VAR with value VAL to the executable's environment
# --set-default VAR VAL : like --set, but only adds VAR if not already set in
# the environment
# --unset VAR : remove VAR from the environment
# --chdir DIR : change working directory (use instead of --run "cd DIR")
# --add-flags ARGS : prepend ARGS to the invocation of the executable
# (that is, *before* any arguments passed on the command line)
# --append-flags ARGS : append ARGS to the invocation of the executable
# (that is, *after* any arguments passed on the command line)
# --prefix ENV SEP VAL : suffix/prefix ENV with VAL, separated by SEP
# --suffix
# To troubleshoot a binary wrapper after you compiled it,
# use the `strings` command or open the binary file in a text editor.
makeWrapper() { makeBinaryWrapper "$@"; }
makeBinaryWrapper() {
local NIX_CFLAGS_COMPILE= NIX_CFLAGS_LINK=
local original="$1"
local wrapper="$2"
shift 2
assertExecutable "$original"
mkdir -p "$(dirname "$wrapper")"
makeDocumentedCWrapper "$original" "$@" | \
@cc@ \
-Wall -Werror -Wpedantic \
-Wno-overlength-strings \
-Os \
-x c \
-o "$wrapper" -
}
# Syntax: wrapProgram <PROGRAM> <MAKE-WRAPPER FLAGS...>
wrapProgram() { wrapProgramBinary "$@"; }
wrapProgramBinary() {
local prog="$1"
local hidden
assertExecutable "$prog"
hidden="$(dirname "$prog")/.$(basename "$prog")"-wrapped
while [ -e "$hidden" ]; do
hidden="${hidden}_"
done
mv "$prog" "$hidden"
makeBinaryWrapper "$hidden" "$prog" --inherit-argv0 "${@:2}"
}
# Generate source code for the wrapper in such a way that the wrapper inputs
# will still be readable even after compilation
# makeDocumentedCWrapper EXECUTABLE ARGS
# ARGS: same as makeWrapper
makeDocumentedCWrapper() {
local src docs
src=$(makeCWrapper "$@")
docs=$(docstring "$@")
printf '%s\n\n' "$src"
printf '%s\n' "$docs"
}
# makeCWrapper EXECUTABLE ARGS
# ARGS: same as makeWrapper
makeCWrapper() {
local argv0 inherit_argv0 n params cmd main flagsBefore flagsAfter flags executable length
local uses_prefix uses_suffix uses_assert uses_assert_success uses_stdio uses_asprintf
local resolve_path
executable=$(escapeStringLiteral "$1")
params=("$@")
length=${#params[*]}
for ((n = 1; n < length; n += 1)); do
p="${params[n]}"
case $p in
--set)
cmd=$(setEnv "${params[n + 1]}" "${params[n + 2]}")
main="$main$cmd"$'\n'
n=$((n + 2))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 2 arguments"$'\n'
;;
--set-default)
cmd=$(setDefaultEnv "${params[n + 1]}" "${params[n + 2]}")
main="$main$cmd"$'\n'
uses_stdio=1
uses_assert_success=1
n=$((n + 2))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 2 arguments"$'\n'
;;
--unset)
cmd=$(unsetEnv "${params[n + 1]}")
main="$main$cmd"$'\n'
uses_stdio=1
uses_assert_success=1
n=$((n + 1))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 1 argument"$'\n'
;;
--prefix)
cmd=$(setEnvPrefix "${params[n + 1]}" "${params[n + 2]}" "${params[n + 3]}")
main="$main$cmd"$'\n'
uses_prefix=1
uses_asprintf=1
uses_stdio=1
uses_assert_success=1
uses_assert=1
n=$((n + 3))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 3 arguments"$'\n'
;;
--suffix)
cmd=$(setEnvSuffix "${params[n + 1]}" "${params[n + 2]}" "${params[n + 3]}")
main="$main$cmd"$'\n'
uses_suffix=1
uses_asprintf=1
uses_stdio=1
uses_assert_success=1
uses_assert=1
n=$((n + 3))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 3 arguments"$'\n'
;;
--chdir)
cmd=$(changeDir "${params[n + 1]}")
main="$main$cmd"$'\n'
uses_stdio=1
uses_assert_success=1
n=$((n + 1))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 1 argument"$'\n'
;;
--add-flags)
flags="${params[n + 1]}"
flagsBefore="$flagsBefore $flags"
uses_assert=1
n=$((n + 1))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 1 argument"$'\n'
;;
--append-flags)
flags="${params[n + 1]}"
flagsAfter="$flagsAfter $flags"
uses_assert=1
n=$((n + 1))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 1 argument"$'\n'
;;
--argv0)
argv0=$(escapeStringLiteral "${params[n + 1]}")
inherit_argv0=
n=$((n + 1))
[ $n -ge "$length" ] && main="$main#error makeCWrapper: $p takes 1 argument"$'\n'
;;
--inherit-argv0)
# Whichever comes last of --argv0 and --inherit-argv0 wins
inherit_argv0=1
;;
--resolve-argv0)
# this gets processed after other argv0 flags
uses_stdio=1
uses_string=1
resolve_argv0=1
;;
*) # Using an error macro, we will make sure the compiler gives an understandable error message
main="$main#error makeCWrapper: Unknown argument ${p}"$'\n'
;;
esac
done
[[ -z "$flagsBefore" && -z "$flagsAfter" ]] || main="$main"${main:+$'\n'}$(addFlags "$flagsBefore" "$flagsAfter")$'\n'$'\n'
[ -z "$inherit_argv0" ] && main="${main}argv[0] = \"${argv0:-${executable}}\";"$'\n'
[ -z "$resolve_argv0" ] || main="${main}argv[0] = resolve_argv0(argv[0]);"$'\n'
main="${main}return execv(\"${executable}\", argv);"$'\n'
[ -z "$uses_asprintf" ] || printf '%s\n' "#define _GNU_SOURCE /* See feature_test_macros(7) */"
printf '%s\n' "#include <unistd.h>"
printf '%s\n' "#include <stdlib.h>"
[ -z "$uses_assert" ] || printf '%s\n' "#include <assert.h>"
[ -z "$uses_stdio" ] || printf '%s\n' "#include <stdio.h>"
[ -z "$uses_string" ] || printf '%s\n' "#include <string.h>"
[ -z "$uses_assert_success" ] || printf '\n%s\n' "#define assert_success(e) do { if ((e) < 0) { perror(#e); abort(); } } while (0)"
[ -z "$uses_prefix" ] || printf '\n%s\n' "$(setEnvPrefixFn)"
[ -z "$uses_suffix" ] || printf '\n%s\n' "$(setEnvSuffixFn)"
[ -z "$resolve_argv0" ] || printf '\n%s\n' "$(resolveArgv0Fn)"
printf '\n%s' "int main(int argc, char **argv) {"
printf '\n%s' "$(indent4 "$main")"
printf '\n%s\n' "}"
}
addFlags() {
local n flag before after var
# Disable file globbing, since bash will otherwise try to find
# filenames matching the the value to be prefixed/suffixed if
# it contains characters considered wildcards, such as `?` and
# `*`. We want the value as is, except we also want to split
# it on on the separator; hence we can't quote it.
local reenableGlob=0
if [[ ! -o noglob ]]; then
reenableGlob=1
fi
set -o noglob
# shellcheck disable=SC2086
before=($1) after=($2)
if (( reenableGlob )); then
set +o noglob
fi
var="argv_tmp"
printf '%s\n' "char **$var = calloc(${#before[@]} + argc + ${#after[@]} + 1, sizeof(*$var));"
printf '%s\n' "assert($var != NULL);"
printf '%s\n' "${var}[0] = argv[0];"
for ((n = 0; n < ${#before[@]}; n += 1)); do
flag=$(escapeStringLiteral "${before[n]}")
printf '%s\n' "${var}[$((n + 1))] = \"$flag\";"
done
printf '%s\n' "for (int i = 1; i < argc; ++i) {"
printf '%s\n' " ${var}[${#before[@]} + i] = argv[i];"
printf '%s\n' "}"
for ((n = 0; n < ${#after[@]}; n += 1)); do
flag=$(escapeStringLiteral "${after[n]}")
printf '%s\n' "${var}[${#before[@]} + argc + $n] = \"$flag\";"
done
printf '%s\n' "${var}[${#before[@]} + argc + ${#after[@]}] = NULL;"
printf '%s\n' "argv = $var;"
}
# chdir DIR
changeDir() {
local dir
dir=$(escapeStringLiteral "$1")
printf '%s' "assert_success(chdir(\"$dir\"));"
}
# prefix ENV SEP VAL
setEnvPrefix() {
local env sep val
env=$(escapeStringLiteral "$1")
sep=$(escapeStringLiteral "$2")
val=$(escapeStringLiteral "$3")
printf '%s' "set_env_prefix(\"$env\", \"$sep\", \"$val\");"
assertValidEnvName "$1"
}
# suffix ENV SEP VAL
setEnvSuffix() {
local env sep val
env=$(escapeStringLiteral "$1")
sep=$(escapeStringLiteral "$2")
val=$(escapeStringLiteral "$3")
printf '%s' "set_env_suffix(\"$env\", \"$sep\", \"$val\");"
assertValidEnvName "$1"
}
# setEnv KEY VALUE
setEnv() {
local key value
key=$(escapeStringLiteral "$1")
value=$(escapeStringLiteral "$2")
printf '%s' "putenv(\"$key=$value\");"
assertValidEnvName "$1"
}
# setDefaultEnv KEY VALUE
setDefaultEnv() {
local key value
key=$(escapeStringLiteral "$1")
value=$(escapeStringLiteral "$2")
printf '%s' "assert_success(setenv(\"$key\", \"$value\", 0));"
assertValidEnvName "$1"
}
# unsetEnv KEY
unsetEnv() {
local key
key=$(escapeStringLiteral "$1")
printf '%s' "assert_success(unsetenv(\"$key\"));"
assertValidEnvName "$1"
}
# Makes it safe to insert STRING within quotes in a C String Literal.
# escapeStringLiteral STRING
escapeStringLiteral() {
local result
result=${1//$'\\'/$'\\\\'}
result=${result//\"/'\"'}
result=${result//$'\n'/"\n"}
result=${result//$'\r'/"\r"}
printf '%s' "$result"
}
# Indents every non-empty line by 4 spaces. To avoid trailing whitespace, we don't indent empty lines
# indent4 TEXT_BLOCK
indent4() {
printf '%s' "$1" | awk '{ if ($0 != "") { print " "$0 } else { print $0 }}'
}
assertValidEnvName() {
case "$1" in
*=*) printf '\n%s\n' "#error Illegal environment variable name \`$1\` (cannot contain \`=\`)";;
"") printf '\n%s\n' "#error Environment variable name can't be empty.";;
esac
}
setEnvPrefixFn() {
printf '%s' "\
void set_env_prefix(char *env, char *sep, char *prefix) {
char *existing = getenv(env);
if (existing) {
char *val;
assert_success(asprintf(&val, \"%s%s%s\", prefix, sep, existing));
assert_success(setenv(env, val, 1));
free(val);
} else {
assert_success(setenv(env, prefix, 1));
}
}
"
}
setEnvSuffixFn() {
printf '%s' "\
void set_env_suffix(char *env, char *sep, char *suffix) {
char *existing = getenv(env);
if (existing) {
char *val;
assert_success(asprintf(&val, \"%s%s%s\", existing, sep, suffix));
assert_success(setenv(env, val, 1));
free(val);
} else {
assert_success(setenv(env, suffix, 1));
}
}
"
}
resolveArgv0Fn() {
printf '%s' "\
char *resolve_argv0(char *argv0) {
if (strchr(argv0, '/') != NULL) {
return argv0;
}
char *path = getenv(\"PATH\");
if (path == NULL) {
return argv0;
}
char *path_copy = strdup(path);
if (path_copy == NULL) {
return argv0;
}
char *dir = strtok(path_copy, \":\");
while (dir != NULL) {
char *candidate = malloc(strlen(dir) + strlen(argv0) + 2);
if (candidate == NULL) {
free(path_copy);
return argv0;
}
sprintf(candidate, \"%s/%s\", dir, argv0);
if (access(candidate, X_OK) == 0) {
free(path_copy);
return candidate;
}
free(candidate);
dir = strtok(NULL, \":\");
}
free(path_copy);
return argv0;
}
"
}
# Embed a C string which shows up as readable text in the compiled binary wrapper,
# giving instructions for recreating the wrapper.
# Keep in sync with makeBinaryWrapper.extractCmd
docstring() {
printf '%s' "const char * DOCSTRING = \"$(escapeStringLiteral "
# ------------------------------------------------------------------------------------
# The C-code for this binary wrapper has been generated using the following command:
makeCWrapper $(formatArgs "$@")
# (Use \`nix-shell -p makeBinaryWrapper\` to get access to makeCWrapper in your shell)
# ------------------------------------------------------------------------------------
")\";"
}
# formatArgs EXECUTABLE ARGS
formatArgs() {
printf '%s' "${1@Q}"
shift
while [ $# -gt 0 ]; do
case "$1" in
--set)
formatArgsLine 2 "$@"
shift 2
;;
--set-default)
formatArgsLine 2 "$@"
shift 2
;;
--unset)
formatArgsLine 1 "$@"
shift 1
;;
--prefix)
formatArgsLine 3 "$@"
shift 3
;;
--suffix)
formatArgsLine 3 "$@"
shift 3
;;
--chdir)
formatArgsLine 1 "$@"
shift 1
;;
--add-flags)
formatArgsLine 1 "$@"
shift 1
;;
--append-flags)
formatArgsLine 1 "$@"
shift 1
;;
--argv0)
formatArgsLine 1 "$@"
shift 1
;;
--inherit-argv0)
formatArgsLine 0 "$@"
;;
esac
shift
done
printf '%s\n' ""
}
# formatArgsLine ARG_COUNT ARGS
formatArgsLine() {
local ARG_COUNT LENGTH
ARG_COUNT=$1
LENGTH=$#
shift
printf '%s' $' \\\n '"$1"
shift
while [ "$ARG_COUNT" -gt $((LENGTH - $# - 2)) ]; do
printf ' %s' "${1@Q}"
shift
done
}
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