find_library
------------

Find a library.

::

   find_library(<VAR> name1 [path1 path2 ...])

This is the short-hand signature for the command that is sufficient in
many cases.  It is the same as find_library(<VAR> name1 [PATHS path1
path2 ...])

::

   find_library(
             <VAR>
             name | NAMES name1 [name2 ...] [NAMES_PER_DIR]
             [HINTS path1 [path2 ... ENV var]]
             [PATHS path1 [path2 ... ENV var]]
             [PATH_SUFFIXES suffix1 [suffix2 ...]]
             [DOC "cache documentation string"]
             [NO_DEFAULT_PATH]
             [NO_CMAKE_ENVIRONMENT_PATH]
             [NO_CMAKE_PATH]
             [NO_SYSTEM_ENVIRONMENT_PATH]
             [NO_CMAKE_SYSTEM_PATH]
             [CMAKE_FIND_ROOT_PATH_BOTH |
              ONLY_CMAKE_FIND_ROOT_PATH |
              NO_CMAKE_FIND_ROOT_PATH]
            )

This command is used to find a library.  A cache entry named by <VAR>
is created to store the result of this command.  If the library is
found the result is stored in the variable and the search will not be
repeated unless the variable is cleared.  If nothing is found, the
result will be <VAR>-NOTFOUND, and the search will be attempted again
the next time find_library is invoked with the same variable.  The
name of the library that is searched for is specified by the names
listed after the NAMES argument.  Additional search locations can be
specified after the PATHS argument.  If ENV var is found in the HINTS
or PATHS section the environment variable var will be read and
converted from a system environment variable to a cmake style list of
paths.  For example ENV PATH would be a way to list the system path
variable.  The argument after DOC will be used for the documentation
string in the cache.  PATH_SUFFIXES specifies additional
subdirectories to check below each search path.

If NO_DEFAULT_PATH is specified, then no additional paths are added to
the search.  If NO_DEFAULT_PATH is not specified, the search process
is as follows:

1.  Search paths specified in cmake-specific cache variables.  These
are intended to be used on the command line with a -DVAR=value.  This
can be skipped if NO_CMAKE_PATH is passed.

::

   <prefix>/lib/<arch> if CMAKE_LIBRARY_ARCHITECTURE is set, and
   <prefix>/lib for each <prefix> in CMAKE_PREFIX_PATH
   CMAKE_LIBRARY_PATH
   CMAKE_FRAMEWORK_PATH

2.  Search paths specified in cmake-specific environment variables.
These are intended to be set in the user's shell configuration.  This
can be skipped if NO_CMAKE_ENVIRONMENT_PATH is passed.

::

   <prefix>/lib/<arch> if CMAKE_LIBRARY_ARCHITECTURE is set, and
   <prefix>/lib for each <prefix> in CMAKE_PREFIX_PATH
   CMAKE_LIBRARY_PATH
   CMAKE_FRAMEWORK_PATH

3.  Search the paths specified by the HINTS option.  These should be
paths computed by system introspection, such as a hint provided by the
location of another item already found.  Hard-coded guesses should be
specified with the PATHS option.

4.  Search the standard system environment variables.  This can be
skipped if NO_SYSTEM_ENVIRONMENT_PATH is an argument.

::

   PATH
   LIB

5.  Search cmake variables defined in the Platform files for the
current system.  This can be skipped if NO_CMAKE_SYSTEM_PATH is
passed.

::

   <prefix>/lib/<arch> if CMAKE_LIBRARY_ARCHITECTURE is set, and
   <prefix>/lib for each <prefix> in CMAKE_SYSTEM_PREFIX_PATH
   CMAKE_SYSTEM_LIBRARY_PATH
   CMAKE_SYSTEM_FRAMEWORK_PATH

6.  Search the paths specified by the PATHS option or in the
short-hand version of the command.  These are typically hard-coded
guesses.

On Darwin or systems supporting OS X Frameworks, the cmake variable
CMAKE_FIND_FRAMEWORK can be set to empty or one of the following:

::

   "FIRST"  - Try to find frameworks before standard
              libraries or headers. This is the default on Darwin.
   "LAST"   - Try to find frameworks after standard
              libraries or headers.
   "ONLY"   - Only try to find frameworks.
   "NEVER" - Never try to find frameworks.

On Darwin or systems supporting OS X Application Bundles, the cmake
variable CMAKE_FIND_APPBUNDLE can be set to empty or one of the
following:

::

   "FIRST"  - Try to find application bundles before standard
              programs. This is the default on Darwin.
   "LAST"   - Try to find application bundles after standard
              programs.
   "ONLY"   - Only try to find application bundles.
   "NEVER" - Never try to find application bundles.

The CMake variable CMAKE_FIND_ROOT_PATH specifies one or more
directories to be prepended to all other search directories.  This
effectively "re-roots" the entire search under given locations.  By
default it is empty.  It is especially useful when cross-compiling to
point to the root directory of the target environment and CMake will
search there too.  By default at first the directories listed in
CMAKE_FIND_ROOT_PATH and then the non-rooted directories will be
searched.  The default behavior can be adjusted by setting
CMAKE_FIND_ROOT_PATH_MODE_LIBRARY.  This behavior can be manually
overridden on a per-call basis.  By using CMAKE_FIND_ROOT_PATH_BOTH
the search order will be as described above.  If
NO_CMAKE_FIND_ROOT_PATH is used then CMAKE_FIND_ROOT_PATH will not be
used.  If ONLY_CMAKE_FIND_ROOT_PATH is used then only the re-rooted
directories will be searched.

The default search order is designed to be most-specific to
least-specific for common use cases.  Projects may override the order
by simply calling the command multiple times and using the NO_*
options:

::

   find_library(<VAR> NAMES name PATHS paths... NO_DEFAULT_PATH)
   find_library(<VAR> NAMES name)

Once one of the calls succeeds the result variable will be set and
stored in the cache so that no call will search again.

When more than one value is given to the NAMES option this command by
default will consider one name at a time and search every directory
for it.  The NAMES_PER_DIR option tells this command to consider one
directory at a time and search for all names in it.

If the library found is a framework, then VAR will be set to the full
path to the framework <fullPath>/A.framework.  When a full path to a
framework is used as a library, CMake will use a -framework A, and a
-F<fullPath> to link the framework to the target.

If the global property FIND_LIBRARY_USE_LIB64_PATHS is set all search
paths will be tested as normal, with "64/" appended, and with all
matches of "lib/" replaced with "lib64/".  This property is
automatically set for the platforms that are known to need it if at
least one of the languages supported by the PROJECT command is
enabled.
