[cmake-developers] SONAME on APPLE?

[Stephen Kelly]

Hi there,

The patch at:

https://codereview.qt-project.org/#change,30084

sets the IMPORTED_SONAME on linux for Qt 5 IMPORTED targets. I don't know 
whether it should also be set on APPLE, but I have now done some 
investigation.

I created a dummy project to test the output created by CMake when 
generating IMPORTING targets with install(EXPORT).

It seems that on APPLE, otool -D <the_lib> will output the "shared library 
id name". I don't know for certain that it is the same thing (I know very 
little about APPLE), but CMake seems to set that based on the name of the 
library, the SOVERSION property, and the file suffix. So far it seems 
similar to the SONAME reported by objdump on linux.

CMake seems to populate the "shared library id name" (Let's call it SONAME 
for now, even on APPLE) with a full path when the library is in the build 
directory ("/Users/kdab/dev/cmake/build/libcmakeqt.5.dylib"), and without 
the path when installed (Only "libcmakeqt.5.dylib"). 

I don't know if that is configurable.

I didn't find any way to create 'frameworks' with CMake, so I don't know if 
there is even the concept of a SONAME when creating a 'framework' on APPLE.

Running otool -D on QtCore from Qt 5 (configured with -no-frameworks), I get 
a full path to the install location when running it on the binaries in both 
the build location and the install location.

Running otool -D on QtCore from Qt 5 (configured as it is by default, that 
is, with -frameworks), I get a full versioned path to 
QtCore.framework/Versions/5/QtCore in the install location when run on 
QtCore.framework/QtCore in both the build dir and the install dir.

CMake seems to use this information to compute the link line, so it would 
seem advantagous that I set it correctly on relevant platforms. Can anyone 
add clarity to anything I wrote? Should I set the IMPORTED_SONAME to these 
full paths to the installation location on APPLE? Wouldn't that make the 
frameworks non-relocatable, or is that a bug in Qt anyway?

Thanks,

Steve.