RE: [GNU-make] Tricky problem filtering out commas from a string.

[Rakesh Sharma]

Hello DaveK,
I was going though the GNU Make mailing list & somehow stumbled upon a 
very-oldquery that you had posted on this list.
You were reporting a problem due to comma variables. But actually the problemis 
not that, rather it is the age-old problem of make allowing the use of 
undefinedvariables to collapse into an empty string!
The culprit is on line #10 and 11.On line-11, the variable 
`LIST2_WITHOUT_COMMAS' is used whereas a line beforeon line-10, 
`LIST_WITHOUT_COMMAS' is initialized. Due to which an empty stringis output.
We could prevent such issues by not resorting to creating new variables for 
intermediateresults, like as,
>    10  LIST_WITHOUT_COMMAS:=$(filter-out $(IMMCOMMA),$(LIST_WITH_COMMAS))>    
> 11  $(warning $(LIST2_WITHOUT_COMMAS))
$(warning $(filter-out $(IMMCOMMA),$(LIST_WITH_COMMAS)))

Or, with a newer version of GNU make, there is an option 
"--warn-undefined-variables"which when run on your makefile "comma.mk" will 
blurt out:
$   make    --warn-undefined-variables    -f   comma.mk                  
comma.mk: 11:  warning: undefined variable 'LIST2_WITH_COMMAS'
With regards,  Rakesh S.

P.S.:  By any chance, are you the David Korn of the Kornshell ?

>On 19 April 2007 14:06, Paul Smith wrote:>>> On Thu, 2007-04-19 at 13:15 
>+0100, Dave Korn wrote:>>>>> The obvious first approach - escape the comma so 
>that filter-out doesn't>>> think it's the separator between its two arguments 
>- just doesn't work.  I>>> can't quite see how to achieve this in make....>>>> 
>Using backslashes as an escape character in make is pretty ad hoc; it>> 
>definitely does not work everywhere you expect it to (unfortunately).>>  I 
>wondered if that might be the case.>>> However, you should be able to do it 
>with variables:>>>>     COMMA = ,>>     LIST_WITHOUT_COMMAS:=$(filter-out 
>$(COMMA),$(LIST_WITH_COMMAS))>>  Doesn't actually work in practice:  as Danny 
>pointed out, filter-out only>matches entire words, but using a variable 
>enabled subst to work.>>/tmp $ cat -n comma.mk>     1>     2  
>LIST_WITH_COMMAS:= foo, bar, baz, quux>     3>     4  COMMA = ,>     5  
>IMMCOMMA:= ,>     6>     7  LIST_WITHOUT_COMMAS:=$(filter-out 
>$(COMMA),$(LIST_WITH_COMMAS))>     8  $(warning $(LIST_WITHOUT_COMMAS))>     
>9>    10  LIST_WITHOUT_COMMAS:=$(filter-out $(IMMCOMMA),$(LIST_WITH_COMMAS))>  
>  11  $(warning $(LIST2_WITHOUT_COMMAS))>    12>    13  
>LIST3_WITHOUT_COMMAS:=$(subst $(COMMA), ,$(LIST_WITH_COMMAS))>    14  
>$(warning $(LIST3_WITHOUT_COMMAS))>    15>    16  
>LIST4_WITHOUT_COMMAS:=$(subst $(IMMCOMMA), ,$(LIST_WITH_COMMAS))>    17  
>$(warning $(LIST4_WITHOUT_COMMAS))>    18>    19>    20>    21  all:>    22    
>      @>/tmp $ /bin/make -f comma.mk>comma.mk:8: foo, bar, baz, 
>quux>comma.mk:11:>comma.mk:14: foo  bar  baz  quux>comma.mk:17: foo  bar  baz  
>quux>make: `all' is up to date.>>  Thanks to all :)>>    cheers,>      
>DaveK>-->Can't think of a witty .sigline today....