Linux v6.6.1 - builtin_func

# SPDX-License-Identifier: GPL-2.0

# 'info' prints the argument to stdout.
$(info,hello world 0)

# 'warning-if', if the first argument is y, sends the second argument to stderr,
# and the message is prefixed with the current file name and line number.
$(warning-if,y,hello world 1)

# 'error-if' is similar, but it terminates the parsing immediately.
# The following is just no-op since the first argument is not y.
$(error-if,n,this should not be printed)

# Shorthand
warning = $(warning-if,y,$(1))

# 'shell' executes a command, and returns its stdout.
$(warning,$(shell,echo hello world 3))

# Every newline in the output is replaced with a space,
# but any trailing newlines are deleted.
$(warning,$(shell,printf 'hello\nworld\n\n4\n\n\n'))

# 'filename' is expanded to the currently parsed file name,
# 'lineno' to the line number.
$(warning,filename=$(filename))
$(warning,lineno=$(lineno))