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(make.info)Testing Flags

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Conditionals that Test Flags
============================

   You can write a conditional that tests `make' command flags such as
`-t' by using the variable `MAKEFLAGS' together with the `findstring'
function (Note: Functions for String Substitution and Analysis.
).  This is useful when `touch' is not enough to make a file
appear up to date.

   The `findstring' function determines whether one string appears as a
substring of another.  If you want to test for the `-t' flag, use `t'
as the first string and the value of `MAKEFLAGS' as the other.

   For example, here is how to arrange to use `ranlib -t' to finish
marking an archive file up to date:

     archive.a: ...
     ifneq (,$(findstring t,$(MAKEFLAGS)))
             +touch archive.a
             +ranlib -t archive.a
     else
             ranlib archive.a
     endif

The `+' prefix marks those command lines as "recursive" so that they
will be executed despite use of the `-t' flag.  Note: Recursive Use of
`make'.