Fpm: compiler flags and warnings

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Hi all,

I am now using fpm for a fortran project and I have two questions:

First: it doesn’t appear to be possible to change the default compiler flags corresponding to the build and debug profiles. When looking at the output from `fpm build --verbose’, I can see that the compiler flags are:

-cpp -Wall -Wextra -fPIC -fmax-errors=1 -g -fcheck=bounds -fcheck=array-temps -fbacktrace -fcoarray=single -fopenmp

However, if, for example, I wanted to have -fcheck=all enabled, I could call fpm build --flag -fcheck=all, (and I would also have to manually add the other flags which I would like to keep). Ideally, I would like to be able to configure the default compiler flags corresponding to the debug and release profiles, so that I don’t have to remember or copy/paste the flags each time. Based on the manifest reference it doesn’t seem possible to do it within fpm.toml. Therefore, are my only options to:

a) Modify the environment variable FPM_FFLAGS? When I do this I see that the flag is added to the default flags, but it doesn’t seem to allow differentiating between debug and release builds nor does it allow for removing any of the default flags.

b) Write a script which calls fpm? Therefore I can configure the script to always call fpm with whichever flags I like using --flag. Then I can have a different script (or define my own flags for the script) for debug vs release builds. Or

c) Use a makefile for complete build control? I would prefer not to do this since I’ve never used make and would rather avoid having to learn another new tool (also I’m on windows so it’s slightly more annoying).

I’m leaning toward option b) since it seems relatively simple, but I’m wondering if I’m missing something more straightforward. And is the lack of configuration available through the manifest intended or is this something which may be added in future releases?

Second: when I call fpm build, the warnings for each file (from -Wall and -Wextra) are written to log files in the build folder. However, I would like to see the warnings directly when I run fpm build. Is it possible to tell fpm to print the warnings directly to the terminal? Or to a single file. I don’t see such an option available in the documentation. The inconvenience here is that if I have several modules I have to manually check each log file in order to see any compiler warnings. Here I can also write script to automate this (e.g., to combine all the log files), but I was wondering if I can avoid this.

I am quite new to formal software development procedures, so feel free to correct me if I have some fundamental misunderstanding in terms of how I’m approaching fpm as a tool.

Thank you for any and all help with this!

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Regarding your first problem, have you tried response files? You can create a fpm.rsp file and create several profiles to build/test/run your projects. I’ve found this very useful and easy to use.

Here a very simple example fast_math/fpm.rsp at main · jalvesz/fast_math · GitHub

Once you have a rsp in your project you can then do fpm @your_profile

Your option b) is also a very good one, you can find something like that for stdlib here stdlib/config/fypp_deployment.py at 38485d8eca7dfb726254a638265c790e858d7cea · fortran-lang/stdlib · GitHub for inspiration

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Okay, yes the response file solution seems very simple. I saw it in fpm --help but it seems to not be super well documented and I didn’t really understand it. If I ever want to do more complicated stuff the python script looks like a good choice. Thank you!

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We had the design for supporting this worked out and mostly implemented, but it didn’t quite get over the finish line.

If anyone has interest and time to update this and get it finished I’d be happy to provide guidance and support.

Yes. Use the --verbose option. I.e. fpm build --verbose.

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Response files were expected to be superseded by the manifest file (fpm.tom) options, as those would be part of the project and so portably
would help set options needed by dependencies as well. They are a feature of the M_CLI2 command line parser and documented in greater detail at

https://urbanjost.github.io/M_CLI2/set_args.3m_cli2.html

They get a good deal of usage, so perhaps a more extensive description
should be added that could be invoked via “fpm help response” somewhat like the extended description of the --runner option can be seen via “fpm help runner”.

Perhaps the highest risk using a script is whether it can run in both MSWindows and GNU/Linux and Unix if multiple environments are supported, particularly if the package will be shared with others. But by definition, a script is very flexible. One variant is instead of calling fpm from the script, the script can be written as an alternate “compiler” and then setting FPM_COMPILER invokes that script.

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