Array

variablecloudinessgmail.com wrote:
>> myBinary: myBinary.o $(filter-out $(wildcard
myLibrary.so), myLibrary.so)
>>         g++ --go-go-gadget-linker
>>
>> With the above rule myBinary depends on
myLibrary.so if it doesn't
>> already exist. But if the file already exist it
doesn't care if it is
>> newer than myBinary.
> 
> Perfect!  Thanks!  I don't claim to understand how
that works, but it
> does work.

The above uses two functions, filter-out and wildcard.
Filter-out is used
to remove strings from a variable, eg:

$(filter-out hello world, hello big world) 

would only leave the word "big" left.

Wildcard is used to search for files that exist, it is
usually used
something like this:

$(wildcard *.c)

The above might return something like "hello.c
world.c".

When using $(wildcard myLibrary.so) it will return
myLibrary.so if the
file already exist. If the file doesn't exist it will
return an empty
string. Using the empty string in filter-out will return the
filename,
when wildcard returns the filename filter-out will return an
empty string.

> The problem with dropping the dependency was that if I
do a 'make clean'
> then a 'make -j 4 all' (all is a target that depends
on all the .so
> files and all of the binaries), the binary may be
linked before the .so
> file is created, which is an error.

If this is an error you might still get trouble. If you
change enough
files so that both the binary and the library needs to be
rebuilt the
binary might still be finished before the library is
finished.

regards Henrik
-- 
The address in the header is only to prevent spam. My real
address is:
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