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SoC-2025-Microprojects.md

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SoC 2025 Applicant Microprojects

Introduction

First make sure you read and understand our general guidelines and suggestions for microprojects.

There are some suggestions on how you can find some microprojects on your own in the document.

Ideas for microprojects

Fix Sign Comparison Warnings in Git's Codebase

Help improve Git's code quality by fixing sign comparison warnings in files that currently disable these warnings. The goal is to remove instances of DISABLE_SIGN_COMPARE_WARNINGS macro and fix the underlying issues properly.

Steps to Complete

  1. Find a C source file that contains #define DISABLE_SIGN_COMPARE_WARNINGS

  2. Remove this #define

  3. Build Git with DEVELOPER=1 to enable compiler warnings. The DEVLEOPER can be specified in your config.mak or as follows

    make DEVELOPER=1 -j4

  4. Fix all -Wsign-compare warnings that appear for that file:

    • Pay attention to comparisons between signed and unsigned integers
    • Modify variable types or add appropriate casts as needed
    • Ensure the fixes don't change the code's behavior

Notes

  • Each file should be handled in a separate patch
  • Follow Git's commit message conventions
  • Test your changes thoroughly
  • This is part of an ongoing effort to enable -Wsign-compare globally

Related Patches

For context on why this is a crucial improvement to Git's codebase, checkout this e-mail by Patrick Steinhardt.

Modernize Test Path Checking in Git's Test Suite

Help improve Git's test suite by converting old-style path checks to use modern helper functions. We'll be replacing basic shell test commands like test -f with Git's dedicated test helpers like test_path_is_file.

Steps to Complete

  1. Find a test script using old-style path checks:

    git grep "test -[efd]" t/

  2. Look for patterns like:

    test -f path/to/file      # old way
test_path_is_file path/to/file    # new way

test -d some/directory    # old way
test_path_is_dir some/directory   # new way

  3. Important: Only replace checks that are actually testing for conditions, not those used in flow control. For example:

    # DON'T change this - it's flow control
if test -e "file.txt"; then
    do_something
fi

# DO change this - it's a test assertion
test -e "file.txt" || error "file.txt should exist"

Notes

  • Start small: Pick a test file with just a few instances to convert
  • Run the test suite after your changes to ensure nothing breaks
  • Follow Git's commit message style
  • Include which command you used to find the instances in your commit message

Need Help?

  • Reference this discussion for detailed examples.
  • If you can't find any instances to fix, let us know what search command you used

Add more builtin patterns for userdiff

"git diff" shows the function name corresponding to each hunk after the @@ ... @@ line. For common languages (C, HTML, Ada, Matlab, ...), the way to find the function name is built-in Git's source code as regular expressions (see userdiff.c). A few languages are common enough to deserve a built-in driver, but are not yet recognized. For example, shell.

This project requires a very good knowledge of regular expressions.

It is easy though to find examples of how this can be done by searching the code base and the mailing list archive, as this has already been done for a number of languages.

Replace a run_command*() call by direct calls to C functions

See for example what Junio did in ffcb4e94d3 (bisect: do not run show-branch just to show the current commit, 2021-07-27).

If you can't find one please tell us, along with the command you used to search, so that we can remove this microproject idea.

Avoid suppressing git's exit code in test scripts

The Git project uses a large collection of integration tests written in Shell to guard against regressions when adding new features or fixing bugs. The scripts in question can be found in the t directory here.

While it is perfectly OK to use pipes when writing integration tests, we must be careful to avoid writing a pipeline that suppresses the exit code of a Git process, like so:

git <subcommand> | <some other command>

...since the exit code of git <subcommand> would be suppressed by the pipe. If git <subcommand> crashed, we would not catch it in the above example when running the integration suite.

Other examples to avoid include:

# bad:
<some command> $(git <subcommand>)

# also bad:
<some command> <<EOF
... some text ...
$(git <subcommand>)
EOF

...since the exit code of git <subcommand> is hidden behind the subshell in both instances.

On the other hand, both of the following examples are OK, since neither hides the exit code of running git <subcommand>:

# good:
var=$(git <subcommand>)

# also good:
<some command> | <some other command> | git <subcommand>

(provided that neither <some command> or <some other command> are git).

See the commit c6f44e1da5 for example, and then do the same thing in one other test script.

If you can't find one please tell us, along with the command you used to search, so that we can remove this microproject idea.

Use unsigned integral type for collection of bits.

Pick one field of a structure that (1) is of signed integral type and (2) is used as a collection of multiple bits. Discuss if there is a good reason why it has to be a signed integral field and change it to an unsigned type otherwise. [thread]

Even though the amount of code to write is small, these projects involve a lot of prior work to understand the specification and deal with all potential corner-cases.

Modernize a test script

A number of our test scripts have been written a long time ago in a style that is now outdated.

In the following email it is explained in details how to modernize and clean up the t7001 test script:

https://lore.kernel.org/git/CAPig+cQpUu2UO-+jWn1nTaDykWnxwuEitzVB7PnW2SS_b7V8Hg@mail.gmail.com/

t7001 is not the only test script where similar changes could be made though.

Find one test script that needs some of the same changes and make them. Please make sure that the test script is not already being worked on by asking on the mailing list before starting to work on it.

There should be only one kind of change per commit. For example if one of your commits indents test bodies with TABs, instead of spaces, then this should be the only kind of change in this commit.