URL:
<http://savannah.gnu.org/bugs/?49093>
Summary: ifdef checks for non-empty value, not definition
Project: make
Submitted by: dduvall
Submitted on: Wed 14 Sep 2016 09:57:06 PM GMT
Severity: 3 - Normal
Item Group: Bug
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Component Version: 4.2.1
Operating System: POSIX-Based
Fixed Release: None
Triage Status: None
_______________________________________________________
Details:
The info doc for "ifdef" is inconsistent. It first says
If the value of that variable has a non-empty value, the
TEXT-IF-TRUE is effective
but then later says
Note that 'ifdef' only tests whether a variable has a value.
It does not expand the variable to see if that value is
nonempty.
Perhaps I'm reading one of those two bits wrong?
At any rate, there seems to be a discrepancy in behavior between "ifdef" and
$(origin). Again, perhaps there's something I'm missing, but the following
makefile demonstrates the issue. If I leave VAR set to empty, then ifdef
thinks VAR is undefined, but origin thinks it's defined. If I set VAR to a
non-empty value, both think it's defined. If I remove the line entirely or
add "undefine VAR", then both think it's undefined. I see this behavior with
4.2.1 and with 3.82.
VAR=
ifdef VAR
$(info ifdef thinks VAR is defined)
else
$(info ifdef thinks VAR is undefined)
endif
ifneq "$(origin VAR)" "undefined"
$(info ifneq/origin thinks VAR is defined)
else
$(info ifneq/origin thinks VAR is undefined)
endif
all:
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