[CMake] Re: Find* and cross compiling

[Rodolfo Schulz de Lima]

> By setting the mode to ONLY cmake will look ONLY in the directories with 
> the
> CMAKE_FIND_ROOT_PATH prefix.

Yes, I do this. The problem is that those scripts hardwire some default 
paths to the native places where headers and libraries are found. When we 
cross-compile, those defaults should be changed. If the scripts didn't 
hardwire those default paths, they'd use the correct defaults set up by 
CMake.

For instance, look at what FindOpenAL does:

FIND_PATH(OPENAL_INCLUDE_DIR al.h
  PATHS
  $ENV{OPENALDIR}
  NO_DEFAULT_PATH
  PATH_SUFFIXES include/AL include/OpenAL include
)
FIND_PATH(OPENAL_INCLUDE_DIR al.h
  PATHS ${CMAKE_PREFIX_PATH} # Unofficial: We are proposing this.
  NO_DEFAULT_PATH
  PATH_SUFFIXES include/AL include/OpenAL include
)
FIND_PATH(OPENAL_INCLUDE_DIR al.h
  PATHS
  ~/Library/Frameworks
  /Library/Frameworks
  /usr/local
  /usr
  /sw # Fink
  /opt/local # DarwinPorts
  /opt/csw # Blastwave
  /opt
  [HKEY_LOCAL_MACHINE\\SOFTWARE\\Creative\ Labs\\OpenAL\ 1.1\ Software\ 
Development\ Kit\\1.00.0000;InstallDir]
  PATH_SUFFIXES include include/lua51 include/lua5.1 include/lua
)

This could be changed to

FIND_PATH(OPENAL_INCLUDE_DIR al.h
    PATHS
    $ENV{OPENALDIR}
    [HKEY_LOCAL_MACHINE\\SOFTWARE\\Creative\ Labs\\OpenAL\ 1.1\ Software\ 
Development\ Kit\\1.00.0000;InstallDir]
    PATH_SUFFIXES include/AL include/OpenAL include)

By not using NO_DEFAULT_PATH, FIND_PATH relies on the correctly default 
search locations set up by cmake. I'm don't know about Mac frameworks and 
stuff, but cross-compilation should always be in mind when writing those 
scripts.
Other native locations (as /sw, /opt/local, /opt/csw) should only be 
searched if not cross-compiling.

Regards,
rod