[CMake] Confusion on how find_package works.

[Robert Dailey]

Trust me, I've read this already. It makes no sense to me. How am I supposed
to know that any of the variables it is checking have been set? And if so,
where were they set? Could someone give me a summary of what find_path is
searching in in this specific case?

On Tue, Jan 13, 2009 at 4:20 PM, Michael Jackson <
mike.jackson at bluequartz.net> wrote:

> From the Help page:
>
> All CMake commands
>
>        • find_path: Find the directory containing a file.
> find_path(<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_path(<VAR> name1 [PATHS path1 path2 ...])
>
> find_path(
> <VAR>
> name | NAMES name1 [name2 ...]
> [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 directory containing the named file. A cache
> entry named by <VAR> is created to store the result of this command. If the
> file in a directory 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_path is invoked with the same variable. The name of
> the file in a directory 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>/include for each <prefix> in CMAKE_PREFIX_PATH
> CMAKE_INCLUDE_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>/include for each <prefix> in CMAKE_PREFIX_PATH
> CMAKE_INCLUDE_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
> INCLUDE
> 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>/include for each <prefix> in CMAKE_SYSTEM_PREFIX_PATH
> CMAKE_SYSTEM_INCLUDE_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_INCLUDE. 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_path(<VAR> NAMES name PATHS paths... NO_DEFAULT_PATH)
> find_path(<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 searching for frameworks, if the file is specified as A/b.h, then the
> framework search will look for A.framework/Headers/b.h. If that is found the
> path will be set to the path to the framework. CMake will convert this to
> the correct -F option to include the file.
>
> ---
> Mike Jackson                 www.bluequartz.net
>
>
>
>
> On Jan 13, 2009, at 5:08 PM, Robert Dailey wrote:
>
>  Hi,
>>
>> I'm currently looking at FindZLIB.cmake trying to understand how it works
>> and I just can't seem to make sense of it. I have a few questions:
>>        • How does find_path() know where to look? Where is it looking?
>> Where is it told where to look?
>>        • Question #1 with find_library() as well.
>> It would be great to be able to set a root directory with all my libraries
>> in it and have it recursively go through it and find the file it is looking
>> for. This would be a convenient (but slow) way of getting find_path() and
>> find_library() to work reliably in my case. Thanks in advance for any help.
>> _______________________________________________
>> CMake mailing list
>> CMake at cmake.org
>> http://www.cmake.org/mailman/listinfo/cmake
>>
>
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