# UE5.4.0-preview-1: C2248 'TMemoryWriterBase\<TSizedDefaultAllocator\<32\>\>::IndexSize': cannot access private member declared in class 'TMemoryWriterBase\<TSizedDefaultAllocator\<32\>\>'

**URL:** <https://forums.unrealengine.com/t/ue5-4-0-preview-1-c2248-tmemorywriterbase-tsizeddefaultallocator-32-indexsize-cannot-access-private-member-declared-in-class-tmemorywriterbase-tsizeddefaultallocator-32/1774878>\
**Category:** Programming & Scripting\
**Tags:** unreal-engine\
**Created:** [March 27, 2024, 5:25pm UTC](https://forums.unrealengine.com/t/ue5-4-0-preview-1-c2248-tmemorywriterbase-tsizeddefaultallocator-32-indexsize-cannot-access-private-member-declared-in-class-tmemorywriterbase-tsizeddefaultallocator-32/1774878 "2024-03-27T17:25:43Z")\
**Posts on this page:** 1\
**Showing post:** 19

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**Author:** ![kiruru002](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@kiruru002](https://forums.unrealengine.com/u/kiruru002)\
**Post date:** [February 10, 2025, 3:52pm UTC](https://forums.unrealengine.com/t/ue5-4-0-preview-1-c2248-tmemorywriterbase-tsizeddefaultallocator-32-indexsize-cannot-access-private-member-declared-in-class-tmemorywriterbase-tsizeddefaultallocator-32/1774878/19 "2025-02-10T15:52:59Z")

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> [@Default member initializers for bit-fields requires at least '/std:c++20'](https://forums.unrealengine.com/t/default-member-initializers-for-bit-fields-requires-at-least-std-c-20/1795109/20):
>
> This is the only solution that worked for me.

For me, who uses UE5.5, the fix didn’t work, but I got a hint from another thread I was looking at recently, and

```auto
CppStandard = CppStandardVersion.Cpp20;

```

I was able to successfully build by putting it in build.cs instead.

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