Conditionals that Test 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 (see 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, the following shows 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. See Recursive use of make.

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