make: Libraries/Search
4.5.6 Directory Search for Link Libraries
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Directory search applies in a special way to libraries used with the
linker. This special feature comes into play when you write a
prerequisite whose name is of the form '-lNAME'. (You can tell
something strange is going on here because the prerequisite is normally
the name of a file, and the _file name_ of a library generally looks
like 'libNAME.a', not like '-lNAME'.)
When a prerequisite's name has the form '-lNAME', 'make' handles it
specially by searching for the file 'libNAME.so', and, if it is not
found, for the file 'libNAME.a' in the current directory, in directories
specified by matching 'vpath' search paths and the 'VPATH' search path,
and then in the directories '/lib', '/usr/lib', and 'PREFIX/lib'
(normally '/usr/local/lib', but MS-DOS/MS-Windows versions of 'make'
behave as if PREFIX is defined to be the root of the DJGPP installation
tree).
For example, if there is a '/usr/lib/libcurses.a' library on your
system (and no '/usr/lib/libcurses.so' file), then
foo : foo.c -lcurses
cc $^ -o $@
would cause the command 'cc foo.c /usr/lib/libcurses.a -o foo' to be
executed when 'foo' is older than 'foo.c' or than
'/usr/lib/libcurses.a'.
Although the default set of files to be searched for is 'libNAME.so'
and 'libNAME.a', this is customizable via the '.LIBPATTERNS' variable.
Each word in the value of this variable is a pattern string. When a
prerequisite like '-lNAME' is seen, 'make' will replace the percent in
each pattern in the list with NAME and perform the above directory
searches using each library file name.
The default value for '.LIBPATTERNS' is 'lib%.so lib%.a', which
provides the default behavior described above.
You can turn off link library expansion completely by setting this
variable to an empty value.
Info Catalog
make: Implicit/Search
make: Directory Search