[GRASS-dev] Replace GNU Indent with ClangFormat?

GRASS GRASS developer
1

Formatting the C and C++ code, making a consistent coding style was proposed for G8 [1]. Unfortunately, it didn't make it. There were attempts to do this [2, 3], but numerous problem arose using `util/grass_indent.sh` and its batch script `util/grass_indent_ALL.sh`, which are based on GNU Indent [4]. These problem are probably originate in the comparatively limited functionality and lack of active development on GNU Indent.

I just filed a PR [5] with the aim to replace GNU Indent with ClangFormat [6] and later (separately!) make a bulk formatting of all the code. Running clang-format on all *.h|*.c|*.cpp (some 3000+) files goes fine without any issues. I have created a `.clang-format` file with the settings as close as possible to the ones in `grass_indent.sh` (somewhat outdated described in [7]).

ClangFormat is a working program in active development, therefore its performance is version dependent (similar to what we have had with Black for Python). On the other hand, its adaptation is increasing, now used in several big and small projects.

Now the question is first of all: is using ClangFormat something the GRASS dev community (you) would want or could live with for this project?
And if so, what version of ClangFormat should then be the starting point (what do you have reasonably easy available for your dev platform)? The present settings in the PR are derived from ClangFormat 13, but could possibly be back ported if really needed.

Please check out the settings, as well as some code files formatted for illustrational purposes only, at the PR [5].

Best,
Nicklas

[1] https://trac.osgeo.org/grass/wiki/Grass8Planning#Codeorganisationcodingstyles
[2] https://github.com/OSGeo/grass/issues/1630
[3] https://github.com/OSGeo/grass/pull/2270
[4] https://www.gnu.org/software/indent/
[5] https://github.com/OSGeo/grass/pull/2272
[6] https://clang.llvm.org/docs/ClangFormat.html
[7] https://trac.osgeo.org/grass/wiki/Submitting/C#Indentation

2

+1

On Ubuntu 20.04 LTS, there is ClangFormat 12, I suppose there will be 13 in the upcoming 22.04 release.

Anna

On Mon, Mar 21, 2022 at 10:01 AM Nicklas Larsson via grass-dev <grass-dev@lists.osgeo.org> wrote:

Formatting the C and C++ code, making a consistent coding style was proposed for G8 [1]. Unfortunately, it didn’t make it. There were attempts to do this [2, 3], but numerous problem arose using util/grass_indent.sh and its batch script util/grass_indent_ALL.sh, which are based on GNU Indent [4]. These problem are probably originate in the comparatively limited functionality and lack of active development on GNU Indent.

I just filed a PR [5] with the aim to replace GNU Indent with ClangFormat [6] and later (separately!) make a bulk formatting of all the code. Running clang-format on all .h|.c|*.cpp (some 3000+) files goes fine without any issues. I have created a .clang-format file with the settings as close as possible to the ones in grass_indent.sh (somewhat outdated described in [7]).

ClangFormat is a working program in active development, therefore its performance is version dependent (similar to what we have had with Black for Python). On the other hand, its adaptation is increasing, now used in several big and small projects.

Now the question is first of all: is using ClangFormat something the GRASS dev community (you) would want or could live with for this project?
And if so, what version of ClangFormat should then be the starting point (what do you have reasonably easy available for your dev platform)? The present settings in the PR are derived from ClangFormat 13, but could possibly be back ported if really needed.

Please check out the settings, as well as some code files formatted for illustrational purposes only, at the PR [5].

Best,
Nicklas

[1] https://trac.osgeo.org/grass/wiki/Grass8Planning#Codeorganisationcodingstyles
[2] https://github.com/OSGeo/grass/issues/1630
[3] https://github.com/OSGeo/grass/pull/2270
[4] https://www.gnu.org/software/indent/
[5] https://github.com/OSGeo/grass/pull/2272
[6] https://clang.llvm.org/docs/ClangFormat.html
[7] https://trac.osgeo.org/grass/wiki/Submitting/C#Indentation

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3

On Mon, 21 Mar 2022 at 10:01, Nicklas Larsson via grass-dev <grass-dev@lists.osgeo.org> wrote:

…There were attempts to do this [2, 3], but numerous problem arose…which are based on GNU Indent [4]. These problem are probably originate in the comparatively limited functionality and lack of active development on GNU Indent.

Additionally, the C++ support in GNU Indent is limited:

While an attempt was made to get indent working for C++, it will not do a good job on any C++ source except the very simplest.

https://www.gnu.org/software/indent/manual/indent/Bugs.html

I think the note in the docs was there even before C++11.

I have created a .clang-format file with the settings as close as possible to the ones in grass_indent.sh (somewhat outdated described in [7]).

I don’t think the style is set in stone. This is perhaps for a next phase, but unless a strong standard emerges for C/C++, we may consider switching to something which is close to Black given our mixed code base. Function signatures and calls would be the big change there. However, the closing parenthesis on a separate line typical to Black is available only in the upcoming ClangFormat 14.

On the other hand, yielding to some 3rd party standard seems like a good idea especially for all the C++ syntax.

Now the question is first of all: is using ClangFormat something the GRASS dev community (you) would want or could live with for this project?

+1. Being tool-independent is not possible here and ClangFormat seems to do the job.

And if so, what version of ClangFormat should then be the starting point (what do you have reasonably easy available for your dev platform)? The present settings in the PR are derived from ClangFormat 13, but could possibly be back ported if really needed.

You can run a specific version locally using Docker thanks to a related GitHub Action:

https://github.com/DoozyX/clang-format-lint-action#run-locally

Harder to integrate in your editor, but at least something. (Yes, your favorite editor may already have support for ClangFormat.)

4

pirmd., 2022. g. 21. marts, plkst. 16:01 — lietotājs Nicklas Larsson
via grass-dev (<grass-dev@lists.osgeo.org>) rakstīja:

Now the question is first of all: is using ClangFormat something the GRASS dev community (you) would want or could live with for this project?

Yes! +1 from me – helps to avoid accidental reformatting of files
while changing small things.

Best,
Nicklas

Māris.

5

+1

FYI - on Fedora:
clang-format --version
clang-format version 13.0.0 (Fedora 13.0.0-3.fc35)

Markus

On Mon, Mar 21, 2022 at 6:43 PM Anna Petrášová <kratochanna@gmail.com> wrote:

+1

On Ubuntu 20.04 LTS, there is ClangFormat 12, I suppose there will be 13 in the upcoming 22.04 release.

Anna

On Mon, Mar 21, 2022 at 10:01 AM Nicklas Larsson via grass-dev <grass-dev@lists.osgeo.org> wrote:

Formatting the C and C++ code, making a consistent coding style was proposed for G8 [1]. Unfortunately, it didn't make it. There were attempts to do this [2, 3], but numerous problem arose using `util/grass_indent.sh` and its batch script `util/grass_indent_ALL.sh`, which are based on GNU Indent [4]. These problem are probably originate in the comparatively limited functionality and lack of active development on GNU Indent.

I just filed a PR [5] with the aim to replace GNU Indent with ClangFormat [6] and later (separately!) make a bulk formatting of all the code. Running clang-format on all *.h|*.c|*.cpp (some 3000+) files goes fine without any issues. I have created a `.clang-format` file with the settings as close as possible to the ones in `grass_indent.sh` (somewhat outdated described in [7]).

ClangFormat is a working program in active development, therefore its performance is version dependent (similar to what we have had with Black for Python). On the other hand, its adaptation is increasing, now used in several big and small projects.

Now the question is first of all: is using ClangFormat something the GRASS dev community (you) would want or could live with for this project?
And if so, what version of ClangFormat should then be the starting point (what do you have reasonably easy available for your dev platform)? The present settings in the PR are derived from ClangFormat 13, but could possibly be back ported if really needed.

Please check out the settings, as well as some code files formatted for illustrational purposes only, at the PR [5].

Best,
Nicklas

[1] https://trac.osgeo.org/grass/wiki/Grass8Planning#Codeorganisationcodingstyles
[2] https://github.com/OSGeo/grass/issues/1630
[3] https://github.com/OSGeo/grass/pull/2270
[4] https://www.gnu.org/software/indent/
[5] https://github.com/OSGeo/grass/pull/2272
[6] https://clang.llvm.org/docs/ClangFormat.html
[7] https://trac.osgeo.org/grass/wiki/Submitting/C#Indentation

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