GNU Info

(make.info)Libraries/Search

---

Prev: Implicit/Search Up: Directory Search

---

Enter node , (file) or (file)node

Directory Search for Link Libraries
-----------------------------------

   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' 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).

   If that file is not found, then the file `libNAME.a' is searched
for, in the same directories as above.

   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 that library filename.  If no library is found, the next
word in the list will be used.

   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.