我无法理解 makefile 中 patsubst 的输出

Question

这是有罪的 makefile :

$ cat -n example.mak
     1  define this
     2          $(patsubst $(1)/%.o,%.o,why_this_does/that.o)
     3          $(patsubst butnot/%.o,%.o, butnot/but_not_that.o)
     4  endef
     5
     6  why:
     7          $(info $(call this, why_this_does) ?)

这是我的问题：

$ make -f example.mak 
        why_this_does/that.o
        but_not_that.o ?
make: 'why' is up to date.

Answer 1

根本原因不在patsubst，而在call。 The manual有备注：

A final caution: be careful when adding whitespace to the arguments to call. As with other functions, any whitespace contained in the second and subsequent arguments is kept; this can cause strange effects. It’s generally safest to remove all extraneous whitespace when providing parameters to call.

事实上，如果你更换

$(info $(call this, why_this_does) ?)

来自

$(info $(call this,why_this_does) ?)

你得到你想要的。