infer_clone/website/docs/checker-impurity.md

---
title: "Impurity"
description: "Detects functions with potential side-effects. Same as \"purity\", but implemented on top of Pulse."
---

Detects functions with potential side-effects. Same as "purity", but implemented on top of Pulse.

Activate with `--impurity`.

Supported languages:
- C/C++/ObjC: Experimental
- Java: Experimental
- C#/.Net: Experimental

This is an experimental inter-procedural analysis that detects impure functions. It is meant to be an improvement over the [purity](/docs/next/checker-purity) analysis with a negation on the issue types. For each function, impurity analysis keeps track of not only the impurity of the function but also some additional information such as which parameters/globals the function modifies. It models functions with no summary/model as impure. The analysis relies on [Pulse](/docs/next/checker-pulse) summaries to determine impurity.


## List of Issue Types

The following issue types are reported by this checker:
- [IMPURE_FUNCTION](/docs/next/all-issue-types#impure_function)
- [MODIFIES_IMMUTABLE](/docs/next/all-issue-types#modifies_immutable)
[website] make docs URLs absolute Summary: A bug in docusaurus makes relative URLs fail depending on how the page was accessed, because the URL of a page in docs/ will end in / if accessed directly or via hyperlink, but that / will be omitted when clicking on the sidebar. The final / makes all the difference when interpreting relative URLs so relative URLs are essentially broken. See https://github.com/facebook/docusaurus/issues/2832 for more details. This changes URL generation to generate URLs /docs/next/..., and manually substitute relative URLs that had been written by hand. Also fix a few other things about outdated links/comments. Finally, `make doc-publish`. Reviewed By: dulmarod Differential Revision: D22117187 fbshipit-source-id: 32e2ba7e1 5 years ago			`---`
			`title: "Impurity"`
			`description: "Detects functions with potential side-effects. Same as \"purity\", but implemented on top of Pulse."`
			`---`

			`Detects functions with potential side-effects. Same as "purity", but implemented on top of Pulse.`

			Activate with `--impurity`.

			`Supported languages:`
			`- C/C++/ObjC: Experimental`
			`- Java: Experimental`
[website] Updating website Summary: updating website. The update was triggered by `make doc-publish`. Reviewed By: jvillard Differential Revision: D26424662 fbshipit-source-id: 5be2369cd 4 years ago			`- C#/.Net: Experimental`
[website] make docs URLs absolute Summary: A bug in docusaurus makes relative URLs fail depending on how the page was accessed, because the URL of a page in docs/ will end in / if accessed directly or via hyperlink, but that / will be omitted when clicking on the sidebar. The final / makes all the difference when interpreting relative URLs so relative URLs are essentially broken. See https://github.com/facebook/docusaurus/issues/2832 for more details. This changes URL generation to generate URLs /docs/next/..., and manually substitute relative URLs that had been written by hand. Also fix a few other things about outdated links/comments. Finally, `make doc-publish`. Reviewed By: dulmarod Differential Revision: D22117187 fbshipit-source-id: 32e2ba7e1 5 years ago
			This is an experimental inter-procedural analysis that detects impure functions. It is meant to be an improvement over the [purity](/docs/next/checker-purity) analysis with a negation on the issue types. For each function, impurity analysis keeps track of not only the impurity of the function but also some additional information such as which parameters/globals the function modifies. It models functions with no summary/model as impure. The analysis relies on [Pulse](/docs/next/checker-pulse) summaries to determine impurity.


			`## List of Issue Types`

			`The following issue types are reported by this checker:`
			`- [IMPURE_FUNCTION](/docs/next/all-issue-types#impure_function)`
[website] Updating website Summary: updating website. The update was triggered by `make doc-publish`. Reviewed By: jvillard Differential Revision: D26424662 fbshipit-source-id: 5be2369cd 4 years ago			`- [MODIFIES_IMMUTABLE](/docs/next/all-issue-types#modifies_immutable)`