Re: Did $(if $(myvar),...) behavior change from make 3.81 to make 4.1?

[Paul Smith]

On Mon, 2017-06-12 at 18:26 -0500, David Drinnan wrote:
> I have a makefile that works just fine in make 3.81 on RHEL 6.8, but
> quickly fails with make 4.1 on Ubuntu 16.04.
> 
> It's failing on this line (details changed, but same logic):
> 
> $(if $(myvar),myothervar := abc,myothervar := xyz)
> 
> with error message:
> 
> build.mk:3: *** empty variable name.  Stop.

This is an issue in the parser.  I doesn't matter whether myvar is empty
or not, that's not what it's complaining about.  The problem is that the
parser is interpreting this as a target-specific variable assignment,
not a normal variable assignment.  That is, instead of expanding to:

  myothervar := abc

it's expanding as if you'd written:

  myothervar :   = abc

which is a target-specific variable assignment with an empty variable
name.

This is a bug: it would be greatly helpful if you could file this on
Savannah, here: https://savannah.gnu.org/bugs/?func=additem&group=make


As for workarounds, the simplest one is to move the if-statement into
the right-hand side; I'm not sure why you need to include the entire
assignment in the if-statement.  Like this:

    myothervar := $(if $(myvar),abc,xyz)