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Future Support for int128 in MSVC and C++ Standard Roadmap

Abhishek K 10 Reputation points
2025-04-17T05:49:59.5666667+00:00

Hi ,

We currently rely on a custom implementation for 128-bit integer support in our cross-platform codebase, due to the absence of native int128/uint128 support in MSVC.

Could you please confirm:

  1. Is there any plan or intent within Microsoft to support native 128-bit integer types (__int128, or similar) in MSVC in future versions?
  2. Is there any discussion or proposal in the C++ standards committee regarding standardized 128-bit integer support in upcoming versions of the language?

Understanding this would help us make informed decisions about continuing to maintain our custom 128-bit abstraction layer vs. preparing for a potential transition to native support.

Looking forward to your insights.

Developer technologies | C++
Developer technologies | C++
A high-level, general-purpose programming language, created as an extension of the C programming language, that has object-oriented, generic, and functional features in addition to facilities for low-level memory manipulation.
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  1. Spencer Simpson 0 Reputation points
    2025-12-18T17:31:31.3866667+00:00

    Extended integer types like __int128 are defined by the C++ standard (since it incorporates the relevant portion of the C standard), but implementing such types is left up to the compiler vendor. It's entirely up to Microsoft to decide whether to put them into Visual C++.

    There was a long discussion in the Visual Studio developer forums about a feature request for __int128, but it got bogged down in red herrings.

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