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<p style="margin-top:0;margin-bottom:0">Thanks Craig,</p>
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<p style="margin-top:0;margin-bottom:0">we are already doing roughly that, plus some custom logic we built around options to be able to forward them to the second CMake process.
<br>
</p>
<p style="margin-top:0;margin-bottom:0">It's a bit more complex for us, but the concepts are the same.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">The problem is just being able to use targets for the version of the executables compiled for the host, instead of using find_program or hardcoding paths like you do at step (e) in your StackOverflow answer.</p>
<p style="margin-top:0;margin-bottom:0"><br>
</p>
<p style="margin-top:0;margin-bottom:0">It wouldn't be that important if all people using our internal CMake API were also CMake experts, but unfortunately we have lots of baffled developers by having to call "find_program()" and then variables, instead of
"find_package(pkg REQUIRED<span class="n"> NO_CMAKE_FIND_ROOT_PATH</span>)" and then use an imported target. Also, this is asymmetrical when non-crosscompiling, which adds more logic than necessary in several places.</p>
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</p>
<p style="margin-top:0;margin-bottom:0">Cheers,<br>
</p>
<p style="margin-top:0;margin-bottom:0">Matteo Settenvini<br>
</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Craig Scott <craig.scott@crascit.com><br>
<b>Sent:</b> Thursday, July 12, 2018 12:00:18 AM<br>
<b>To:</b> Settenvini, Matteo<br>
<b>Cc:</b> cmake@cmake.org<br>
<b>Subject:</b> Re: [CMake] Cannot import a project twice when cross compiling (as host-tool and for the target arch)</font>
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<div dir="ltr">Not quite sure if it fits your use case, but we use a technique at work basically as described in the following:
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<div><a href="https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fstackoverflow.com%2Fquestions%2F36084785%2Fbuilding-a-tool-immediately-so-it-can-be-used-later-in-same-cmake-run&data=01%7C01%7C%7C19358ac4692f4ef2cce208d5e779b1f5%7C6d4034cd72254f72b85391feaea64919%7C1&sdata=xJ%2FHdGlj4O%2FRulWQNQY6nWhpodk3sBpiDM6EucQJXZk%3D&reserved=0" originalsrc="https://stackoverflow.com/questions/36084785/building-a-tool-immediately-so-it-can-be-used-later-in-same-cmake-run" shash="E4Xhz69vkQSaL8JOQGTRRe3XqrO992+f2tSmOf1mklMZx9POI+9AHQ7cM070V10ZeqLbi2NJwM8qPTQkngpJENBjD2+BPiyWgeH3xlwr34sldP7zDW7HRGmyDAqHvr+Yp3Na08XGeT1U3OtK7Uc5H+kXy7g8QeZR+betkq5BFK4=">https://stackoverflow.com/questions/36084785/building-a-tool-immediately-so-it-can-be-used-later-in-same-cmake-run</a></div>
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<div>Your case sounds more complicated, but maybe the above technique might help if you can organise things that way.<br>
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<div class="x_gmail_extra"><br>
<div class="x_gmail_quote">On Wed, Jul 11, 2018 at 10:54 PM, Settenvini, Matteo <span dir="ltr">
<<a href="mailto:matteo.settenvini@here.com" target="_blank">matteo.settenvini@here.com</a>></span> wrote:<br>
<blockquote class="x_gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
Dear all,<br>
<br>
I have the following problem which I don't know how to best solve.<br>
Any help is appreciated.<br>
<br>
============== Use Case ==============<br>
<br>
Consider the following use case:<br>
<br>
* We are cross-compiling.<br>
* A certain project A depends on project B in two different ways:<br>
- it uses an executable target from B to generate some files, e.g. a compiler.<br>
- one of its libraries links against a library of B.<br>
<br>
We would like to be able to do (not possible with CMake at the moment):<br>
<br>
<br>
find_package(B REQUIRED)<br>
# use B::lib normally. When crosscompiling, it will be the one compiled for the target.<br>
<br>
find_package(B REQUIRED NO_CMAKE_FIND_ROOT_PATH)<br>
# use B::exe knowing that it will always run from the host system.<br>
<br>
<br>
This is for instance a use case we have for flatbuffers / protobuf.<br>
<br>
IMPORTED and ALIAS targets should not be global, or it should be<br>
possible to override them. Or else, it should be possible to<br>
dynamically specify a namespace when importing targets through<br>
find_package().<br>
<br>
I opened a bug at <a href="https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.kitware.com%2Fcmake%2Fcmake%2Fissues%2F18169&data=01%7C01%7C%7C19358ac4692f4ef2cce208d5e779b1f5%7C6d4034cd72254f72b85391feaea64919%7C1&sdata=O2F%2BX4iOCnF7HYxPFBkSobsrqxkyTIhkcFJ3fjeP81k%3D&reserved=0" originalsrc="https://gitlab.kitware.com/cmake/cmake/issues/18169" shash="lOrzgGksWR0JiW5Z2ulY5VVwD0Kxsn8oq7aaJdS3mHBCyPl2desKXReNwGlYIYFgdt0gxAt7B0T1FV+aNbszbzu92YV+8vGms3gSiO3pxewKrFgqhYSQgwwK2VIT0MwVLhfOxMv0ycriGG5L9hOJzsfUTNjNTOjpy7Fub/8vJaE=" rel="noreferrer" target="_blank">
https://gitlab.kitware.com/<wbr>cmake/cmake/issues/18169</a>,<br>
but it got closed as there are no plans to change the way CMake works.<br>
<br>
The issue contains also a test case, if you'd like to try it out.<br>
<br>
============== Problem ==============<br>
<br>
The user cannot import a project twice to get the appropriate targets<br>
when cross-compiling: once for the host architecture and once for the<br>
target architecture.<br>
<br>
Right now, the user needs to manually use e.g. find_program() instead<br>
of relying on installed locations, which can be annoying if the<br>
binaries are installed outside the environment PATH. This can be<br>
worked around, but we would like to use targets in place of<br>
find_program() or find_library() calls.<br>
<br>
The problem is much more apparent in big superbuilds where you have<br>
hundreds of projects brought together in one build and no control over<br>
components outside your own. It is too hard to ensure a stable<br>
configuration order (so that find_package() is always called for the<br>
host version before the target version, or vice-versa).<br>
<br>
============== Help needed ==============<br>
<br>
How would you solve the issue, so that different targets are available<br>
for both the version built for the host and target architectures?<br>
<br>
Note that sometimes these external projects are not under our control,<br>
and they come directly from upstream as git submodules. So we would<br>
like to touch them as little as possible.<br>
<br>
Bests,<br>
Matteo Settenvini<br>
-- <br>
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<div dir="ltr">Craig Scott<br>
<div>Melbourne, Australia</div>
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