:= vs = in make macros

Question

Possible Duplicate:
What is the difference between the GNU Makefile variable assignments =, ?=, := and +=?

I only know very basic makefile syntax, and was reading through another project's makefile and came across := for macro declaration. Why would they use that?

In other words, is there any difference between

MYMACRO = hi i'm a macro

and

MYMACRO := hi i'm a macro

?

http://stackoverflow.com/questions/448910/makefile-variable-assignment — cnicutar, Jun 08 '11 at 18:20
see in particular http://www.gnu.org/software/make/manual/make.html#Flavors — Alexandre C., Jun 08 '11 at 18:20
So there is no difference in the examples of the question, but there would be if MYMACRO used another macro and the value of the other macro could change while the makefile is being processed. — simpleuser, Oct 21 '14 at 22:36
@cnicutar `'info' is not recognized as an internal or external command, operable program or batch file.` — BrainSlugs83, Jul 11 '19 at 01:30

score 129 · Accepted Answer · answered Jun 08 '11 at 18:20

129

Variables defined with := in GNU make are expanded when they are defined rather than when they are used.

answered Jun 08 '11 at 18:20

sverre

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Could you explain some more, what "expand" invokes? – rubo77 Nov 16 '16 at 10:36
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@rubo77 *Expand* mean replacing `$variable` by its `value`. See here for more details http://stackoverflow.com/a/30215530/5016540 – thangdc94 Apr 28 '17 at 08:08
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An example would be beneficial. I found the linked answer in the "duplicate" was a bit more explanatory. – Leo Ufimtsev Aug 18 '17 at 20:57
some example would help here – jersey bean Jun 10 '22 at 21:38

:= vs = in make macros

1 Answers1