[CMake] How to set environment variables with spaces in commands

[Ruslan Baratov]

On 10-Dec-15 12:52, Attila Krasznahorkay wrote:
> Hi QP,
>
> Probably not the intended solution, but what I’m doing in such cases is that in a patch step I create a shell script that does the configuration for me. With all the environment settings and everything. Like:
>
> PATCH_COMMAND ${CMAKE_COMMAND} -E echo “cd someDir/; CC=\”something\” ./configure” > configure.sh
> CONFIGURE_COMMAND sh configure.sh
...

> Unfortunately this makes the code quite unportable, as it will only work on POSIX platforms like this.
Even on *nix platforms such code will not always works as expected. As 
documentation states 
(https://cmake.org/cmake/help/v3.4/module/ExternalProject.html):

    Behavior of shell operators like |&&| is not defined.

I've hit this on practice by using `LOG_* 1` feature. You can try this 
example (I've moved PATCH_COMMAND to CONFIGURE_COMMAND since there is no 
LOG_PATCH option):

    https://gist.github.com/ruslo/e8c7be03521f167ae8f0


Result:

    [ 62%] Performing configure step for 'Foo'
    cd /.../Foo-prefix/src/Foo-build && /.../cmake -P
    /.../Foo-prefix/src/Foo-stamp/Foo-configure-.cmake
    CMake Error at /.../Foo-prefix/src/Foo-stamp/Foo-configure-.cmake:16
    (message):
       Command failed: 1

The reason of the failure is because CMake collect all arguments into 
one command and run execute_process:

    set(command "/.../cmake;-E;echo;cd ..;>;configure.sh")
    execute_process(COMMAND ${command} RESULT_VARIABLE result)

which of course doesn't make sense.

This makes writing ExternalProject_Add steps with modification of 
environment quite non-trivial task (at least doing it correctly). This 
feature definitely missing in CMake. I've mentioned it once already: 
https://cmake.org/pipermail/cmake-developers/2015-August/026053.html

but I've changed my mind about the approach because of LOG_* issue. Now 
I do the next:

* wrap each step with CMake script, i.e. instead of `CC=something 
./configure` do

    set(ENV{CC} "something")
    execute_process(COMMAND ./configure ...)

* run CMake script in *_COMMAND:

    CONFIGURE_COMMAND
    "${CMAKE_COMMAND}" -P "/path/to/configure.cmake"

This makes it cross-platform and *_LOG friendly but require more tricks. 
Like if you're building in source (non-cmake packages) you have to copy 
script before execution since CMake will remove source directory on 
DOWNLOAD step. Which makes it looks like this:

    CONFIGURE_COMMAND
    "${CMAKE_COMMAND}" -E copy "/path/to/source/configure.cmake"
    "/path/to/unpacked/configure.cmake"
    COMMAND
    "${CMAKE_COMMAND}" -P "/path/to/unpacked/configure.cmake"

PS I'm hitting problems in ExternalProject with environment variables 
all the time. E.g. at this moment fixing MinGW + Boost: 
https://github.com/ruslo/hunter/pull/273

Ruslo

>   But I guess that’s the case anyway once you start setting environment variables.
>
> Cheers,
>             Attila
>
> P.S. I often create build.sh and install.sh scripts as well in additional patch commands.
>
>> On Dec 10, 2015, at 5:35 AM, Qingping Hou <dave2008713 at gmail.com> wrote:
>>
>> Hi all,
>>
>> I am trying to setup an ExternalProject in cmake but got stuck in the
>> configuration step. I am using ccache to speed up the compilation:
>>
>> ```
>> ExternalProject_Add(
>>   ...
>>   CONFIGURE_COMMAND CC="ccache arm-linux-gnueabihf-gcc" ./configure
>>   ...
>> )
>> ```
>>
>> However, when cmake generates the Makefile, it moves the quotes around
>> and breaks the command:
>>
>> ```
>> "CC=ccache arm-linux-gnueabihf-gcc" ./configure
>> ```
>>
>> I have tried various escaping method to try to get it work properly
>> without any luck. Is this a bug or an unintended feature?
>>
>> Thanks,
>> QP
>> -- 
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