[CMake] CMake 3.11: Gives wrong paths to ar/strip/etc. when overridden

[Deniz Bahadir]

Am 14.06.2018 um 07:05 schrieb Paul Smith:
> I've discovered that CMake is not correctly locating ar/strip/etc. if I
> override the names of these tools on the command line.  I've tried this
> with 3.5.2 as well and I get the same incorrect behavior.
> 
> Here's an example (this is on a GNU/Linux system):
> 
> $ type -a my-ar
> /work/bin/my-ar
> 
> $ my-ar --version | head -n1
> GNU ar (GNU Binutils) 2.30
> 
> $ pwd
> /tmp/obj
> 
> $ cat ../CMakeLists.txt
> PROJECT(foobar)
> CMAKE_MINIMUM_REQUIRED(VERSION 3.0)
> 
> $ cmake --version | head -n1
> cmake version 3.11.3
> 
> $ cmake -DCMAKE_AR=my-ar ..
>    ...
> 
> $ grep CMAKE_AR CMakeCache.txt
> CMAKE_AR:FILEPATH=/tmp/obj/my-ar
> //ADVANCED property for variable: CMAKE_AR
> CMAKE_AR-ADVANCED:INTERNAL=1
> 
> 
> Note how, instead of either using just "my-ar" or else the fully-
> qualified path "/work/bin/my-ar", CMake uses the bogus and completely
> non-existent path "/tmp/obj/my-ar".  This causes my builds to fail,
> obviously.
> 
> I tried enabling debug-output, trace, and trace-expand but there are no
> clues there as to why CMake prefixes these paths with the local object
> directory.
> 
> I should note that resetting the C and C++ compilers works:
> 
>   * -DCMAKE_C_COMPILER=my-gcc   --> CMAKE_C_COMPILER=/work/bin/my-gcc
>   * -DCMAKE_CXX_COMPILER=my-g++ --> CMAKE_CXX_COMPILER=/work/bin/my-g++

I would not have this expected to work.

> 
> But all the other bintools variable overrides do the wrong thing:
> 
>   * -DCMAKE_AR=my-ar           --> CMAKE_AR=/tmp/obj/my-ar
>   * -DCMAKE_LINKER=my-ld       --> CMAKE_LINKER=/tmp/obj/my-ld
>   * -DCMAKE_RANLIB=my-ranlib   --> CMAKE_RANLIB=/tmp/obj/my-ranlib
>   * -DCMAKE_STRIP=my-strip     --> CMAKE_STRIP=/tmp/obj/my-strip
>   * -DCMAKE_OBJCOPY=my-objcopy --> CMAKE_OBJCOPY=/tmp/obj/objcopy
> 

This is what I would have expected.
If you just give the executable's name as value to the variable an 
implicit "./" is seen by CMake which when translated into an absolute 
path results in "./" being replaced by the current working-directory of 
CMake (which seems to be "/tmp/obj/").

> Can anyone explain this, and hopefully help me find a way to fix it?
> Am I just doing variables wrong here?  How should I do it?

I recommend to us the fully qualified path to your alternative 
executables as values for the variables. That should do the trick.

> 
> Thanks!
> 

HTH,
Deniz

PS: You are right that the behavior seems to be inconsistent for 
different variables and should be similar for all variables. So I 
recommend you file a bug-report in CMake's issue-tracker.