HI Jim. On 07/28/2012 09:32 AM, Jim Meyering wrote: > Stefano Lattarini wrote: >> Sometimes, in our makefiles, we want to assign a default value to a >> variable that might not have been assigned yet. One might think that >> using the GNU make assignment '?=' is enough: >> >> VAR ?= DEFAULT-VALUE >> >> But alas, such an usage allow environment overrides; i.e., if an > > s/an / > s/allow/allows/ > >> environment variable named 'VAR' is present there and defined to, > > s/is present there / > >> say, BAD-VALUE, the construct above will result in the $(VAR) make >> variable being defined to BAD-VALUE, not to DEFAULT-VALUE. >> >> To help overcoming this situation, we define a new make function > > At first I was going to say s/ing//, but how about rewording? > > Use the 'am.vars.is-undef' function to avoid this situation. > It tells whether the given make variable is ... > >> 'am.vars.is-undef', that tells whether the given make variable is >> not "safely" defined, i.e., either undefined, or defined to a value >> that is inherited from the environment. >> Good advice, as usual. I've amended the comments and the commit message following all your suggestions, and pushed.
Thanks, Stefano
