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When using the built-in $(error text) and $(warning text) functions of GNU Make, how can I get line breaks into the error/warning output without acrobatics?
By acrobatics I mean funny methods such as these two:
$(warning $(shell /bin/echo -e "something\nfoo\nbar\nbaz"))
$(warning $(shell /bin/bash -c 'echo -e "something\nfoo\nbar\nbaz"'))
which, btw, didn't work for me with GNU Make 3.81 on Ubuntu 10.04.
Rationale: I want to make the error output in conditional parts (ifeq, ifneq) of my GNUmakefile more readable.
The current workaround for me is to use for each line:
$(warning ...)
and finally for the last line:
$(error ...)
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As in normal makefile syntax, a single logical recipe line can be split into multiple physical lines in the makefile by placing a backslash before each newline. A sequence of lines like this is considered a single recipe line, and one instance of the shell will be invoked to run it.
The ' @ ' is discarded before the line is passed to the shell. Typically you would use this for a command whose only effect is to print something, such as an echo command to indicate progress through the makefile: @echo About to make distribution files.
A backslash ( \ ) followed by a newline character is interpreted as a space in the command. Use a backslash at the end of a line to continue a command onto the next line. NMAKE interprets the backslash literally if any other character, including a space or tab, follows the backslash.
Define a line break variable using define/endef and use it as $n like this:
define n
endef
$(warning "something$nfoo$nbar$nbaz")
Note the two blank lines between define and endef
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