Currently opm-parser does not create opm-parser-config.cmake files. Therefore
building with duncontrol fails as it sets opm-parser_DIR. With this patch
we force CMake to always use module mode for finding which fixes this.
this prevents to check for the same module more than once in the same
cmake run and should thus speed things up a bit as well as make the
output a bit cleaner. For this I assumed that the ${name}_FOUND cmake
variable does not get cached, which it seems like it does not...
Setting CMAKE_DISABLE_FIND_PACKAGE_xxx flag should make find_package
not doing anything, but this does not seem to work with older versions
of CMake. Anyway, we can test this flag and make sure that we don't
call find_package in that case.
Also includes a check for both upper- and same-case versions of found
flag, as some modules, most notably Boost, does not set the upper-case
version of their _FOUND flag; this tests for both.
If it is already found, most packages sets a flag that makes it exit
immediately anyway. We usually cannot rerun find_package to get another
combinations of modules. Here we check the flag before we start looking
for the package to avoid the endless stream of messages.
By returning a ${package}_SOURCES variable with the names of the code,
it will be propagated to ${project}_SOURCES and subsequently compiled
into the library.
AGMG (Algebraic Multigrid) uses this functionality.
The config variables in _CONFIG_IMPL_VARS are only written to config.h
and not the .pc or -config.cmake files. They can thus only be used by
the implementation files and not the headers. Use this set to avoid
exposing the variables to other projects, when it is likely that a
probe used by that other project may turn up a different result.
Markus Blatt
Andreas Lauser
Roland Kaufmann
Atgeirr Flø Rasmussen
Bård Skaflestad