Add QEP 337: Coverity scan cleanup

Author: nyalldawson

qep-337-coverity-scan-cleanup.md

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+# QGIS Enhancement: QGIS (and dependencies) Coverity Scan Cleanup 
+
+**Date** 2025-03-25
+
+**Author** Nyall Dawson (@nyalldawson)
+
+**Contact** [email protected]
+
+**Version** QGIS 3.44-3.46
+
+# Summary
+
+The [Coverity Scan](https://scan.coverity.com/) tool is a highly regarded tool for static analysis of complex
+c++ projects. It's able to pro-actively identify many code issues (such as potential
+crashes, memory leaks, and other unsafe behavior) which aren't picked up by other
+tools (such as clang-tidy or cppcheck).
+
+Having no open issues reported by Coverity Scan allows a project to advertise
+themselves as "Coverity Clean", which is a highly regarded recognition and which forms
+a valuable bullet point when discussing a project's stability and code quality.
+
+While Coverity Scan is a proprietary service, it offers free analysis for
+suitable open-source projects. It has been used sporadically for QGIS analysis
+over the past 10 years, and has directly lead to many fixes and optimisations. 
+
+Currently, the tool reports around 1075 open issues when run on the QGIS master codebase.
+
+These issues range from false positives to trivial fixes through to serious issues
+which require substantial work to fix. Unfortunately, the large number of trivial
+issues currently reported in QGIS make the tool effectively useless for QGIS, as
+the critical issues are hidden amongst the many hundreds of trivial issues.
+
+This project will cleanup the Coverity Scan results by:
+
+1. Marking false-positive issues accordingly in the scan results, so that they no
+  longer clutter the Coverity results reports
+2. Fix trivial issues so that the signal-to-noise ratio of the reports is improved
+
+Unfortunately the Coverity Scan results site is very slow and clunky to navigate,
+so even closing false-positive reports takes a non-negligable amount of time to do!
+
+**Please note that Coverity Scan results are not publicly available due to the
+potential of security risks being exposed, and only approved QGIS core developers
+have access to these reports**
+
+## External projects
+
+Since QGIS embeds a number of third party dependencies (such as MDAL, lazperf, and untwine,
+among others), the scan also includes issues identified in these projects.
+
+During the cleanup I will submit pull requests upstream to these projects, which will
+benefit both the QGIS scan results + other users of these libraries.
+
+## Deliverables
+
+- Removing all false-positive reports from the scan results
+- Fixing trivial issues in QGIS and embedded third party dependencies
+
+If time is available after completing the cleanup, I will investigate whether it is
+possible to automatically run the Coverity Scan tool on a weekly basis as a GitHub
+action (as is done for other projects, e.g. GDAL). **This may not be possible due to
+the size of QGIS and the time required for a full QGIS rebuild under the Coverity Scan
+tool.**
+
+All non-trivial fixes are considered to be out of scope for the project. After the
+cleanup these will be easy to identify and could potentially be targeted in a future
+QGIS bug fixing round.