Language Version

Like many programming languages, Slang experiences a tension between the desire for rapid innovation/evolution and stability. One of the benefits that users of Slang have so far enjoyed has been the rapid pace of innovation in the language and its standard library. However, as developers start to have larger bodies of Slang code, they may become concerned that changes to the language could break existing code. There is no magical way to keep innovating while also keeping the language static.

Slang supports using the #language preprocessor directive, as well as the -std compiler option (CompilerOptionName::LanguageVersion) to specify the language version that a source file is written against. The source file will then be parsed and checked by the compiler using the rules from the specified language version.

Users are advised to provide a #language directive as the first non-whitespace line in their source file, such as:

#language slang 2026

The following version strings are allowed:

  • latest: use the latest language version supported by the current compiler.

  • legacy: use the legacy Slang language.

  • 2018: equivalent to legacy.

  • 2025: Slang language version 2025.

  • 2026: Slang language version 2026.

If no #language line exists and no version is specified via compiler options, the default setting is legacy.

The Legacy Slang Language

When the language version is set to legacy, the compiler behavior will be consistent with the Slang language as in 2018-2023. Specifically:

  • All declarations have public visibility.

  • A module declaration is not required at the start of each module.

Slang 2025

Slang language version 2025 brings these changes on top of the legacy language:

  • All declarations have internal visibility.

  • A module declaration is required at the start of each module.

  • Modifier volatile has been deprecated in Slang. See GitHub issue #10614 for details. The modifier is still accepted in GLSL source code for compatibility reasons.

Slang 2026

Slang language version 2026 brings these changes on top of Slang 2025:

  • Comma expression is removed when it is used inside a parenthesis. The expression (a, b) no longer evaluates to have b’s type as in C/C++. Instead, (a,b) means makeTuple(a,b) and returns a tuple consisting of a and b. See SP#027 for details.

  • Users must explicitly opt in to enable dynamic dispatch with the dyn keyword. More rigorous validations are enabled to make sure dynamic dispatch is not triggered accidentally. See SP#024 for details.

  • Modifier volatile has been removed from Slang. See GitHub issue #10614 for details. The modifier is still accepted in GLSL source code for compatibility reasons.

  • Interface-typed variables can no longer be default-initialized. See GitHub issue #9191 for details.