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falk-werner_webfuse/build/dobuild/bin/parse_make_targets.sh

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#!/bin/sh
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#
# This file is part of dobuild.
# Copyright (c) 2019 Contributors as noted in the AUTHORS file.
#
# SPDX-License-Identifier: MPL-2.0
set -e
# Derived based on https://stackoverflow.com/questions/4219255/how-do-you-get-the-list-of-targets-in-a-makefile
#
# Note: This relies on -p printing the database nonetheless, which is the case as of GNU make 3.82.
# Sadly, GNU make offers no direct option to just print the database.
#
# Invokes make in order to print the database derived from a makefile:
# -p prints the database
# -Rr suppresses inclusion of built-in rules and variables
# -q only tests the up-to-date-status of a target (without remaking anything), but that by itself doesn't
# prevent execution of recipe commands in all cases
# "$@" list of separate commandline parameters (additional make parameters)
# : is a deliberately invalid target that is meant to ensure that no commands are executed;
# 2>&1 1>&3
# redirect stderr to stdout and stdout to fd 3 to allow filtering unwanted error message
# grep -v '.*\s\+No rule to make target\s\+.*:.*' 1>&2
# suppresses the resulting error message - "make: *** No rule to make target ':'. Stop." and redirect
# other output to stderr
# 3>&1 redirect fd 3 back to stdout
print_make_db() {
{ "$MAKE" -pRrq "$@" : 2>&1 1>&3 | grep -v '.*\s\+No rule to make target\s\+.*:.*' 1>&2; } 3>&1
}
export LANG=C
export LC_ALL=C
MAKE="${MAKE:-make}"
print_make_db "$@" \
| awk -v RS= -F: '/^# File/,/^# Finished Make database/ {if ($1 !~ "^[#.]") {print $1}}' \
| sort \
| grep -v -e '^[^[:alnum:]]' -e '[%]$'
# Pipe-chain explanation:
# awk -v RS= -F: '/^# File/,/^# Finished Make database/ {if ($1 !~ "^[#.]") {print $1}}'
# v RS= this is an awk idiom that breaks the input into blocks of contiguous non-empty lines.
# -F: input field speparator
# /^# File/,/^# Finished Make database/
# matches the range of lines in the output that contains all targets (true as of GNU make 3.82) - by limiting
# parsing to this range, there is no need to deal with false positives from other output sections.
# if ($$1 !~ "^[#.]")
# selectively ignores blocks:
# # ... ignores non-targets, whose blocks start with # Not a target:
# . ... ignores special targets
# all other blocks should each start with a line containing only the name of an explicitly defined target
# followed by :
# sort
# sorts the resulting list of targets, which is the best option, since not sorting doesn't produce a helpful
# ordering in that the order in which the targets appear in the makefile is not preserved.
# grep -v -e '^[^[:alnum:]]' -e '[%]$$' removes unwanted targets from the output:
# -v revert machtes
# -e '^[^[:alnum:]]'
# ... hidden targets, which - by convention - are targets that start neither with a letter nor a digit.
# -e '[%]$$'
# ... targets ending with % (pattern targets)