On Thursday 16 February 2012, Alexander Neundorf wrote:
> Hi,
>
> when I use a Find-module to search for a package, I get a nice error
> message if the package could not be found.
I collected the various error messages which can be produced in the different
cases:
* package not found
* package found, but version doesn't match
* REQUIRED
* without REQUIRED
* find_package() with no Find-module present
* find_package(NO_MODULE)
* find_package() with a wrapper Find-module which does:
find_package(ecm QUIET NO_MODULE)
fphsa(ecm CONFIG_MODE)
Here we go:
package not found, REQUIRED:
--------------------------------------------------------
1.) find_package() with no Find-module present:
CMake Error at CMakeLists.txt:4 (find_package):
Could not find module Findecm.cmake or a configuration file
for package ecm.
Adjust CMAKE_MODULE_PATH to find Findecm.cmake or set
ecm_DIR to the directory containing a CMake configuration
file for ecm. The file will have one of the following
names:
ecmConfig.cmake
ecm-config.cmake
***** processing continues, but with error
--------------------------------------------------------
2.) find_package(NO_MODULE):
CMake Error at CMakeLists.txt:4 (find_package):
Could not find a configuration file for package ecm.
Set ecm_DIR to the directory containing a CMake
configuration file for ecm. The file will have one of the
following names:
ecmConfig.cmake
ecm-config.cmake
***** processing continues, but with error
--------------------------------------------------------
3.) find_package() with a wrapper Find-module:
CMake Error at /opt/cmakeHEAD/share/cmake-2.8/Modules/
FindPackageHandleStandardArgs.cmake:91 (MESSAGE):
Could NOT find ecm: found neither ecmConfig.cmake nor ecm-config.cmake
(Required is at least version "0.0.4")
Call Stack (most recent call first):
/opt/cmakeHEAD/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:121
/opt/cmakeHEAD/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:247
Findecm.cmake:4 (find_package_handle_standard_args)
CMakeLists.txt:7 (find_package)
***** processing stops
--------------------------------------------------------
Without REQUIRED the messages are the same (with the wrapper Find-module the
callstack is not printed), but processing continues without error.
Now the cases where the Config file was found, but the version didn't match:
--------------------------------------------------------
4.) find_package() with no Find-module present, same with NO_MODULE:
CMake Error at CMakeLists.txt:4 (find_package):
Could not find a configuration file for package "ecm" that
is compatible with requested version "0.0.4".
The following configuration files were considered but not accepted:
/opt/ecm/share/ecm-0.0.2/cmake/ecm-config.cmake, version: 0.0.2
/opt/ecm/share/ecm-0.0.3/cmake/ecm-config.cmake, version: 0.0.3
***** processing continues, but with error
--------------------------------------------------------
5.) find_package() with a wrapper Find-module:
CMake Error at /opt/cmakeHEAD/share/cmake-2.8/Modules/
FindPackageHandleStandardArgs.cmake:91 (MESSAGE):
Could NOT find ecm (Required is at least version "0.0.4"),
checked the following files:
/opt/ecm/share/ecm-0.0.2/cmake/ecm-config.cmake (version 0.0.2)
/opt/ecm/share/ecm-0.0.3/cmake/ecm-config.cmake (version 0.0.3)
Call Stack (most recent call first):
/opt/cmakeHEAD/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:117
/opt/cmakeHEAD/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:247
Findecm.cmake:4 (find_package_handle_standard_args)
CMakeLists.txt:7 (find_package)
***** processing stops
--------------------------------------------------------
What should be improved:
1.), 2.), 4.) processing should stop if REQUIRED was used
2.) CMAKE_PREFIX_PATH should be mentioned
1.), 2.) if a version number was used, this should be printed in the error
message
1.) CMAKE_PREFIX_PATH should be mentioned at least.
This is the one error message which is IMO problematic. It basically only says
"it did not work", and I don't know whether the package is missing or whether
the buildsystem of the project is broken, which are two significantly
different problems - one requires installing a package, the other requires
hacking the buildsystem of an unknown project.
This could be avoided by making NO_MODULE required when the intention is to
search for a Config file (I would have preferred from the beginning if
find_package() would use only Find-modules, and for searching Config-files
there would have been a separate command like find_config()).
In general, I would still recommend everybody to use the small wrapper Find-
modules also for packages which install a Config.file, if only for the purpose
to contain some documentation or to set up information for
FeatureSummary.cmake.
Alex
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