Makefile compare string input-CodePudding

To understand better string variables in a Makefile, I have tried to do this example :

KEYWORD=Nothing

test:
    $(call myFunc)

define myFunc
ifeq ($(KEYWORD), "Apple")
    echo "You have found the key"
else
    echo "Try again"
endif
endef

But when I'm typing

make test KEYWORD="Fork"

It prints errors

syntax error near unexpected token `Fork,'
`ifeq (Fork, "Apple")'

I have also tried :

Put Apple or 'Apple' in ifeq
Put a space or not after "," : ifeq ($(KEYWORD), "Apple")
Run command with KEYWORD=Fork
Did it using shell (if [ ${KEYWORD} -eq "Apple" ])

I'm running out of ideas because I don't understand how Makefille / Shell interpret the assignment KEYWORD="Fork"

Thanks

CodePudding user response：

First, $(call myfunc) is 100% identical to writing $(myfunc). The call function in make merely expands a variable with some other local values (the arguments) bound first. If you don't provide any local values, then you're just expanding the variable.

Expanding a variable just replaces the variable reference with what it expands to. So writing:

FOO = bar
foo:
        echo $(FOO)

is 100% identical to writing:

foo:
        echo bar

So in your situation,

test:
        $(call myFunc)

is the same as:

test:
        $(myFunc)

which is the same as:

test:
        ifeq ($(KEYWORD), "Apple")
            echo "You have found the key"
        else
            echo "Try again"
        endif

which is why you get the output you did: these are not valid shell commands, but since you've expanded the variable as part of a recipe, they are sent to the shell as part of the recipe.

CodePudding user response：

MadScientist identifies the problem. Perhaps the solution you're looking for is simply evaluating the conditional earlier. eg:

KEYWORD ?= NOTHING
...
ifeq ($(KEYWORD), Apple)
define myFunc
        echo "You have found the key"
endef
else
define myFunc
        echo "Try again"
endef
endif