Stream: wasm-tools

Topic: Making component from modules with pagesize 0x1

view this post on Zulip Antoine Lavandier (May 19 2026 at 15:42):

Hello,

I just updated from wasm-tools from 1.239.0 to 1.249.0. And now I have files that previously could be turned into components with wasm-tools component new now fail with 

error: failed to encode a component from module

Caused by:
    0: failed to validate component output
    1: mismatch in page size for memories (at offset 0x33c9)

I suspect that this is linked to the fact that I have a memory with pagesize 0x1 and is caused by https://github.com/bytecodealliance/wasm-tools/pull/2477. I only have a single memory though that I'm not sure that I understand where's the problem
cc @Alex Crichton since you're the author of the linked PR.

view this post on Zulip Alex Crichton (May 19 2026 at 21:57):

Ah yeah this is from that PR because previously we didn't check all the components of the memory type. Technically the component model doesn't integrate with the custom-page-sizes proposal, but I think this would be reasonable to relax for wasm-tools. @Antoine Lavandier would you be up for sending a PR for this?

view this post on Zulip Antoine Lavandier (May 20 2026 at 11:27):

Sure. That being said, when you say that it would make sense to relax it for wasm-tools. Would you also be open to relax it for wasmtime ? Also, what's the best way to do this ? Currently all memories are checked to be subtypes of MemoryType { initial: 0, maximum: None, memory64: ty.memory64, shared: false, page_size_log2: None };Should we remove this check ? Check against pages_size_log2: Some(0) and page_size_log2: Some(16) and only fail if none work ?

view this post on Zulip Alex Crichton (May 20 2026 at 13:26):

For Wasmtime and wasm-tools we'll still want to require -Wcustom-page-sizes as an opt-in to enable that feature, but I would agree that there shouldn't be any necessary feature other than that.

For wasm-tools it'd probably be easiest to update the check to pick up the page_size_log2 from the original type itself so that way it's guaranteed to be compatible

view this post on Zulip Antoine Lavandier (May 21 2026 at 09:05):

I have opened a PR for this in the wasm-tools repo. For now I'm sticking with wasm-tools 1.246.0 and wasmtime 43 since they're the newest version that still allow component with custom page sizes.

Last updated: Jun 01 2026 at 09:49 UTC