Re: cost of -MP

[Noel Yap]

This shouldn't be the case.

For example:

$ cat GNUmakefile
.PHONY: all
all: my.o

my.o: my.h
        touch $(@)

my.h:
$ ls my.h
ls: my.h: No such file or directory
$ gmake
touch my.o
$ gmake
touch my.o
$ touch my.h
$ gmake
touch my.o
$ gmake
gmake: Nothing to be done for `all'.

$ cat GNUmakefile
.PHONY: all
all: my.o

my.o: my.h
        touch $(@)

.PHONY: my.h
my.h:

$ ls my.h
my.h
$ gmake
touch my.o
$ gmake
touch my.o


IOW, things dependent upon a .PHONY will be rebuilt regardless of the 
dependency's timestamp.  Empty targets are treated differently.

Noel
Boris Kolpackov wrote:

> Noel Yap <address@hidden> writes:
>  
>
> > I misunderstood.  When you said PHONY targets, I thought you meant it 
> > generates ".PHONY: my_header" as well, not just an empty target.
>
>
> No, gcc generates just
>
> header.h:
>
>
> And since there are no commands for this target make assumes it is
> phony.
>
> -boris