---
title: "sourceInformationMarkerStart"
description: "A Compose internal function. DO NOT call directly.

Records the start of a source information marker that can be used for tooling to determine the
source location of the corresponding composable function that otherwise don't require tracking
information such as [ReadOnlyComposable] functions. By default, this function is declared as
having no side-effects. It is safe for code shrinking tools (such as R8 or ProGuard) to remove
it.

Important that both [sourceInformationMarkerStart] and [sourceInformationMarkerEnd] are removed
together or both kept. Removing only one will cause incorrect runtime behavior."
type: "function"
---

<div class='type'>Function</div>


<a id='references'></a>
<div class='sourceset sourceset-common'>Common</div>


```kotlin
@ComposeCompilerApi
public fun sourceInformationMarkerStart(composer: Composer, key: Int, sourceInformation: String)
```


A Compose internal function. DO NOT call directly.

Records the start of a source information marker that can be used for tooling to determine the
source location of the corresponding composable function that otherwise don't require tracking
information such as `ReadOnlyComposable` functions. By default, this function is declared as
having no side-effects. It is safe for code shrinking tools (such as R8 or ProGuard) to remove
it.

Important that both `sourceInformationMarkerStart` and `sourceInformationMarkerEnd` are removed
together or both kept. Removing only one will cause incorrect runtime behavior.