---
name: "PDL::DeveloperGuide"
section: "3pm"
platform: "linux"
package: "pdl"
version: "1:2.100-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/PDL::DeveloperGuide"
---

# PDL::DeveloperGuide(3pm)

How to develop for PDL

## NAME

PDL::DeveloperGuide - How to develop for PDL

## Public Git Repository

The PDL source distribution is hosted with "Git" at the GitHub site \<https://github.com/PDLPorters/pdl\>, alongside with other PDL related software.

This is the preferred place to submit bug reports or, even better, pull requests.

## PDL Developer Guidelines

The following guidelines are for any developer that has access to the PDL Git repository.

- 1\) Add new files to the inventory

  Before committing a change with new files to the repository you should update:

  ```
      - MANIFEST (if files were added, using 'make manifest')
      - MANIFEST.SKIP (if applicable)
  ```

- 2\) Add tests

  Make sure you add a test case in the 't' directory for any significant additional capability you add to PDL.  Please use Test::More or one the of the Test modules available via perl modules rather than doing-it-yourself!

- 3\) Add documentation

  Please include POD documentation for any functions you add to the distribution.

- 4\) Run the tests

  Don't commit before you successfully built and passed `"make test"`.

- 5\) Watch for bug reports

  Bugs should be reported to the GitHub issue tracker at \<https://github.com/PDLPorters/pdl/issues\>.  See PDL::Bugs for a detailed description.

- 6\) PDL Developer Recommended Workflow

  This is detailed in section 4.11 of PDL::FAQ.

## PDL Developer Notes

### Getting (some) Debug Information

PDL has some global variables which control diagnostic output:

- $::PP\_VERBOSE

  If set to a true value, PDL::PP will print details while building the module processing `"pp_def"` declarations.

- $PDL::Graphics::TriD::verbose

  If set to a true value, the routines in PDL::Graphics::TriD will report their progress.

- $PDL::verbose

  Several modules produce diagnostic output to STDOUT if `$PDL::verbose` has a true value.

- $PDL::debug

  Several modules produce diagnostic output if `$PDL::verbose` has a true value.

### Generating a Stack Trace

To generate a stack-trace to help us debug a problem, please first of all do `"make realclean"`, ensure you have the latest released PDL. Then, if it is still happening, please follow this process:

- Rerun perl Makefile.PL

  This will update the timestamps on Makefiles, prompting a full rebuild.

- Edit your generated top-level Makefile

  Add `"-g"` to the `"OPTIMIZE ="` line to generate debug symbols (this gets propagated to subdirectories)

- Run: "make"

  This builds PDL into the `"blib"` directory.

- Run: "gdb perl -ex 'run -Mblib t/tracking.t'"

  In gdb, run: `"bt"`

- Copy-paste the backtrace output

  This should show where the segfault originated.

Then please open an issue on whichever repo is relevant with your `"perl -V"` output and PDL version, together with the stack-trace created above. When you do paste such output into a GitHub issue, please surround such blocks with \`\`\` on their own lines. You can check out how it will render with the "Preview" button above the issue-editing box.

### Random Musings

A (small) collection of random musings to note if you feel the need to improve or add to PDL (please do):

- Organizing Commits

  The preferred way to organize commits is one commit per small, meaningful change (ideally each with an update to the corresponding tests).  This makes it easy in the log to determine what was done and to locate any desired commit in case of issues that need to be resolved.

### Finding the Source

As of 2.096, the directory layout in the repository is largely the same as in a PDL installation, especially in PDL::Basic.

Where the .pm files are generated via PDL::PP, changes would need to go into their .pd sources. Use `"git grep Package::Name"` to find them.

## References

- Official Website

  For the audience of PDL users there is a dedicated website in the perl.org domain: \<https://pdl.perl.org/\>.

- The current PDL version on MetaCPAN

  \<https://metacpan.org/dist/PDL\>

- A guide to PDL's module references for PDL users

  PDL::Modules

- The comprehensive modules index (autogenerated)

  PDL::Index

- Git

  The main Git home page is at \<http://www.git-scm.org/\>. Two good online Git references are:

  - the Git User's Manual at

    \<http://www.kernel.org/pub/software/scm/git/docs/user-manual.html\>

  - and Git Magic at

    \<http://www-cs-students.stanford.edu/~blynn/gitmagic/\>