Conan: [question] Getting 'settings.compiler.libcxx' value not defined in a --pure-c project

[hbobenicio]

• [X] I've read the CONTRIBUTING guide.

Even though I've created a new package with the flag --pure-c, which conanfile.py template configures the deletion of the field self.settings.compiler.libcxx, the command conan create still fails with the error ERROR: : 'settings.compiler.libcxx' value not defined.

Am I doing something wrong? Is that a bug?

Here are the commands:

conan new myproj/1.2.3 --test --pure-c

# generated conanfile.py
    def configure(self):
            del self.settings.compiler.libcxx

conan create . user/testing -s compiler=clang -s compiler.version=10
Exporting package recipe
myproj/1.2.3@user/testing: A new conanfile.py version was exported
myproj/1.2.3@user/testing: Folder: /home/myuser/.conan/data/myproj/1.2.3/user/testing/export
myproj/1.2.3@user/testing: Exported revision: 71b84694e77a8c54b51a1f797a31116a
Configuration:
[settings]
arch=x86_64
arch_build=x86_64
build_type=Release
compiler=clang
compiler.version=10
os=Linux
os_build=Linux
[options]
[build_requires]
[env]

ERROR: : 'settings.compiler.libcxx' value not defined

[memsharded]

Hi @hbobenicio

The issue is that the conan new -t command is generating a test_package that is using C++ (check test_package/example.cpp). Then the settings.compiler.libcxx value is still necessary for building the test_package. You have two options:

• Pass -s compiler.libcxx=libstdc++ in the command line, to specify the missing value for the test_package to know how to build. You can also create your own profile (recommended) and define your settings in profiles files

• Modify the test_package code to contain only an example.c pure C example, and add the same configure() method with the same del self.settings.compiler.libcx in the test_package/conanfile.py file.

Note: we might want to provide a test_package that is pure C too, I am labeling this as a UX improvement.

[hbobenicio]

@memsharded Thanks for the quick explanation!

I got it!

How about when using -t and -c flag at the same time, the test_package/conanfile.py template could already also have the configure method deleting it the same way it does on the projects conanfile.py? Sounds a reasonable feature request?

[memsharded]

How about when using -t and -c flag at the same time, the test_package/conanfile.py template could already also have the configure method deleting it the same way it does on the projects conanfile.py? Sounds a reasonable feature request?

Yes, totally, that was what I was thinking when I said:

we might want to provide a test_package that is pure C too, I am labeling this as a UX improvement.

This would be an easy feature, if you want to try to contribute it yourself 😄

[hbobenicio]

@memsharded I think I can do that ... ;P newbie conan user here, so I gotta take a closer look to the code to see how project templates are used based on the CLI comands/flags. My free time is kind of rare, but let's see what I can do... Should we keep it going with this issue or should we open another with as a feature request instead?

[memsharded]

This issue is good, no need for a new one.

Of course, no pressure, don't worry if you can't do it, someone else will manage. The code is python I hope you know the basics.

If you want to give it a try, the idea is to put new templates in https://github.com/conan-io/conan/blob/develop/conans/client/cmd/new.py, and then add an extra conditional under if test:

Don't hesitate to ask for guidance or help. Thanks!

[hbobenicio]

Hi @memsharded , me again :)

finally got some time to take a look at it. I see that the file is already importing jinja. Is there any reason that those template strings are not jinja templates? The code is using format a lot and I thought if they were all just jinja template things could be easier to manage probably...

I want not that this would become a lot of strings templating refactoring though as I can't see much further how could this impact the rest of the system. What do you think? Should I try to change those to jinja templates?

We could have blocks just like these:

conanfile in jinja template:

    {% if pure_c %}
    def configure(self):
        del self.settings.compiler.libcxx
    {% endif %}

test_conanfile:

    {% if pure_c %}
    def configure(self):
        del self.settings.compiler.libcxx
    {% endif %}

instead of this:

        if pure_c:
            config = "    def configure(self):\n        del self.settings.compiler.libcxx\n"
            files["conanfile.py"] = files["conanfile.py"] + config

[sdmg15]

Hello, is @hbobenicio still interested in working on this? Or I can take it over?

[memsharded]

H @hbobenicio @sdmg15

Sorry for not responding @hbobenicio earlier. We got tons of notifications and sometimes they are buried in the backlog.

I would suggest, for whoever will do this, that separate the feature from the refactor, then do 2 Pull Request:

• One PR to move to jinja2 templates
• Another PR for the "C only" feature.

They could be in any order, not critical.

[hbobenicio]

Sorry guys. I've got really busy on work and on personal things so I couldn't follow this up.

@memsharded thanks for the feedback. agreed.

@sdmg15 feel free to handle it. Thanks!

[memsharded]

Thanks for the follow up @hbobenicio !

Good, assigned to you @sdmg15