Can we use EmccMaximumHeapSize to change the maximum size of the heap to 4gb?

[dlemstra]

I am working on a project that uses Blazor and can use a lot of memory. We would love to have Memory64 support as mentioned in #94108 but for now we are limited to increasing the size of the heap from 2gb to 4gb. But it looks like this is not fully supported? When I enable this in our project I get out of bounds errors that look like an int overflow:

MONO_WASM: jit_call code generation failed: RangeError: Start offset -2038988752 is outside the bounds of the buffer
MONO_WASM: // 1 jit call wrappers generated, blob follows //
MONO_WASM: // #0 === jcp_419b4_0 hasThis=true hasRet=true wasmArgTypes=127,127,127

Assert failed: Overflow: value -956889432 is out of 0 4294967295 range dotnet.native.8.0.2.6av86pdsis.js:8 
Error: Assert failed: Overflow: value -956643752 is out of 0 4294967295 range

Should we be able to use <EmccMaximumHeapSize>4294901760</EmccMaximumHeapSize> to increase the size of the heap or should we not do this? I have created a discussion instead of an issue because I cannot create a small project that reproduces this. It looks like jit_call is part of the Jiterpreter. Is there an option to disable this so we can check if increasing the heap size only causes issues in the Jiterpreter?

[maraf]

You can disable jiterpreter with <BlazorWebAssemblyJiterpreter>false</BlazorWebAssemblyJiterpreter>.
You are using the EmccMaximumHeapSize correctly, I just need to check the max value, because I'm not sure if it can be "all memory" or whether it needs to substract stack size (it is directly passed to emscripten as MAXIMUM_MEMORY and according to their setting it to 4gb should be ok)

[maraf]

I can't get the error you mentioned on my sample.

[maraf]

What version of SDK are you using? (dotnet --info + TargetFramework property from your csproj)

[dlemstra]

I am using the following version:

.NET SDK:
 Version:           8.0.200
 Commit:            438cab6a9d
 Workload version:  8.0.200-manifests.e575128c

And targeting net8.0 in the project with this NuGet package: <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="8.0.2" />.

To check if EmccMaximumHeapSize was working and if we could allocate more than int.MaxValue I added the allocation of an array with int.MaxValue as the size. When doing this early in the program it seems to be causing the issues mentioned earlier and I am also getting out of memory exceptions. But when I do this a bit later in the program I can use more than 2gb:

> getDotnetRuntime(0).Module.HEAP8
Int8Array(317128704) [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, .....

But that doesn't mean the program will continue to work happily. At some point it fails inside assert_int_in_range because buffer_ptr is below zero:

But I am still unable to reproduce this in a sample project. And using <BlazorWebAssemblyJiterpreter>false</BlazorWebAssemblyJiterpreter> had no effect.