[gdal-dev] CMAKE_INSTALL_PREFIX gdalinfo still looks for .dylib in /usr/lib

[Greg Troxel]

Even Rouault <even.rouault at spatialys.com> writes:

> Le 04/07/2022 à 07:32, Brad Hards a écrit :
>> On Monday, 4 July 2022 3:19:55 PM AEST Nik Sands wrote:
>>> Is it expected that these GDAL utilities (such as gdalinfo) would look for
>>> GDAL in /usr/lib instead of the location in which it was actually built?
>> No.
>>
>> I think your conceptual problem is expecting that the GDAL utilities are doing
>> the looking. That isn't how it works. Instead, the system loader does the
>> search based on what the utility says it needs.
>>
>> That is, a dynamically linked gdalinfo says the "what", not the "where".

This isn't entirely accurate.   An executable (or another library) lists
the needed libraries and the search paths.

>> If you put your libraries somewhere non-standard, you need to tell the system
>> where to get them from. Usually LD_LIBRARY_PATH environment variable or
>> something like that will help.

Variables like that can help, but having to set them is working around a bug.

> That would rather be DYLD_LIBRARY_PATH on Mac
>
> Building GDAL with "cmake -DGDAL_SET_INSTALL_RELATIVE_RPATH=ON" might
> also help. Cf
> https://gdal.org/build_hints.html#cmdoption-arg-GDAL_SET_INSTALL_RELATIVE_RPATH

Indeed, cmake is very messy about RPATH.  Some operating systems seem to
object to rpath settings, and for whatever reason, cmake doesn't default
to doing this the way I consider correct, and further seems to push some
of the decisions to the project.  Compare to autoconf/libtool, which has
"the way rpath ought to be" doctrine embedded, which is good if you
agree and not so good if you don't.

So basically you need to understand how shlib searching works, and then
you need to understand the various cmake options, and figure it out.

"objdump -a" is useful to inspect objects on normal systems, and otool
is useful on macOS.  (Despite using and working on pkgsrc for macs I
have not yet fully paged in how shared libraries work on macs.  But
pkgsrc installs programs in /opt/pkg/bin that find libraries in
/opt/pkg/lib just fine.)
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