makefile - Multi-line define in GNU make -

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i'm trying make sense out of multi-line define directive of gnu make , cannot. example:

define 1 2 endef all:     @echo w=$(word 1,$(a))

running make produces result have expected least:

w=1 make: 2: command not found make: *** [all] error 127

it appears part of $(a) has spilled outside $(word) function.

is bug or intended behavior? if "spill" intentional, how works?

p.s. gnu make v3.81 on linux/x64

the $(word) function splitting on spaces. not whitespace, spaces.

there no spaces in a macro nothing gets split.

add trailing space on 1 line or leading space on 2 line , expected behaviour.

this consistent across gnu make 3.81, 3.82, 4.0, , 4.1 in quick testing here.

the reason see "spill" called because of how define expanded. expanded literally, newline , all. (think template expansion.)

so make expands define call $(word 1,...) expands result (the whole define including newline) recipe template , ends 2 lines executes recipe.

consider macro this:

define somecommands echo foo echo bar echo baz endef  all:     $(somecommands)

what expect happen here? how many lines body of all? how many shells run here? commands executed? answer 3 lines, 3 shells , 3 echo commands.

if newlines weren't counted run echo foo echo bar echo baz in 1 command , foo echo bar echo baz output instead of expected (and far more useful) foo, bar, , baz on 3 different lines.


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