[CMake] PKGCONFIG backward compatibility on CVS trunk.

[Bill Hoffman]

Michel Hermier wrote:
> Hi,
>
> I'm experiencing a string against list issue PKGCONFIG new code.
>
> When using it we (in KDE) do things like:
>
> PKGCONFIG(lib libIncDir libLinkDir libLinkFlags LibCFlags)
> FIND_PATH(LIB_INCLUDE_DIR libfile.h ${linInkDir})
> FIND_LIBRARY(LIB_LIBRARIES NAMES libnames ... PATH ${libLinkDir})
>
> This was working for me until the upgrade of the pkgtool util.
>
> It seems that the new pkgtool util return a string instead of a list, 
> making the FIND_FOO methods fails in case of multiple path.
> From what I understand, calling ${BAR} doesn't produce the same number 
> of arguments when expended, and for me it's sounds an unexpected 
> behavior.
> I mean, if I wanted it to be a single argument I would have done "${BAR}"
>
> I attached a little CMakeLists.txt that show the behavior.
> The case is simple I only assign one variable to one string, and one 
> to a list containing the same content of the string.
> And the output is different of the 2 calls is different, while I would 
> expect to have the same output since I don't used "" in the macro call.
>
> Is it something expected or did I miss something ?
I am a bit lost here....

Did the program pkgtool change its output?  
If not, then it was not intentional to break backwards compatibility 
with the new pkgconfg stuff.

A patch was submitted because PlPlot did not work with the changes...

Here is the comment:

    # To be compatible with obsolete module must return blank-delimited 
strings.
    # Also, lead with a blank (for TRUE/FALSE compatibility, 2.4.4 
appears to
    # have returned a blank sometimes followed by nl for the situation
    # where the pkg-config  module has been found [e.g., 
_PKGCONFIG_TMP_FOUND]
    # but does not define the desired quantity.

The old one basically did this:
 EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} ARGS ${_package} --libs 
OUTPUT_VARIABLE ${_link_FLAGS} )

The new one puts it in a cmake list, but the patch puts it back into a 
string separated by spaces.

-Bill