wazero: JIT: Exception 0xc0000005 0x8 0x0 0x0

I’m testing some code with Wazero, and I notice one odd crash, that I’m not sure if it’s either my code (which is Zig) or Wazero. That is strange from previous errors, because it’s one “Exception 0xc0000005 0x8 0x0 0x0”. It’s not an panic or something from testing.Error(err).

I’m using Windows/amd64.

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The log is:

 go test -tags wasi,km,zig -v -bench=. -benchmem -benchtime=5s -cpu 1
=== RUN   TestEncodeObjectAPI
Exception 0xc0000005 0x8 0x0 0x0                                                                                                                                              
PC=0x0                                                                                                                                                                        
                                                                                                                                                                              
github.com/tetratelabs/wazero/internal/wasm/jit.(*callEngine).execWasmFunction(0xc00074a240, {0x5dd008, 0xc00009e140}, 0xc000952e70, 0xc000952cf0)                            
        Z:/GOPATH/pkg/mod/github.com/tetratelabs/wazero@v0.0.0-20220430041858-abd1c79f3335/internal/wasm/jit/engine.go:699 +0x185 fp=0xc00095dbb8 sp=0xc00095dae0 pc=0x4d5305 
github.com/tetratelabs/wazero/internal/wasm/jit.(*moduleEngine).Call(0xc000954030?, {0x5dd008, 0xc00009e140}, 0xc000952e70, 0xc000494dd0, {0xc000954030, 0x1, 0x1})           
        Z:/GOPATH/pkg/mod/github.com/tetratelabs/wazero@v0.0.0-20220430041858-abd1c79f3335/internal/wasm/jit/engine.go:582 +0x48f fp=0xc00095dcb8 sp=0xc00095dbb8 pc=0x4d4b2f 
github.com/tetratelabs/wazero/internal/wasm.(*FunctionInstance).Call(0x53bca0?, {0x5dd008?, 0xc00009e140?}, {0xc000954030?, 0xc000022270?, 0x0?})                             
        Z:/GOPATH/pkg/mod/github.com/tetratelabs/wazero@v0.0.0-20220430041858-abd1c79f3335/internal/wasm/call_context.go:164 +0x63 fp=0xc00095dd08 sp=0xc00095dcb8 pc=0x4901c3
benchmark%2ekarmem%2eorg.(*Wasm).Run(...)
        X:/karmem/benchmark/main_wasi_test.go:289
benchmark%2ekarmem%2eorg.TestEncodeObjectAPI(0xc000061040)
        X:/karmem/benchmark/main_wasi_test.go:113 +0x1f6 fp=0xc00095df70 sp=0xc00095dd08 pc=0x50d556
testing.tRunner(0xc000061040, 0x58dce8)
        C:/Program Files/Go/src/testing/testing.go:1439 +0x102 fp=0xc00095dfc0 sp=0xc00095df70 pc=0x3e3482
testing.(*T).Run.func1()
        C:/Program Files/Go/src/testing/testing.go:1486 +0x2a fp=0xc00095dfe0 sp=0xc00095dfc0 pc=0x3e432a
runtime.goexit()
        C:/Program Files/Go/src/runtime/asm_amd64.s:1571 +0x1 fp=0xc00095dfe8 sp=0xc00095dfe0 pc=0x3587a1
created by testing.(*T).Run
        C:/Program Files/Go/src/testing/testing.go:1486 +0x35f

goroutine 1 [chan receive]:
testing.(*T).Run(0xc000060ea0, {0x57e4e0?, 0x35af53?}, 0x58dce8)
        C:/Program Files/Go/src/testing/testing.go:1487 +0x37a
testing.runTests.func1(0xc000020090?)
        C:/Program Files/Go/src/testing/testing.go:1839 +0x6e
testing.tRunner(0xc000060ea0, 0xc0000c3cd8)
        C:/Program Files/Go/src/testing/testing.go:1439 +0x102
testing.runTests(0xc000094320?, {0x72cd40, 0x1, 0x1}, {0x26848cc0598?, 0x40?, 0x738f20?})
        C:/Program Files/Go/src/testing/testing.go:1837 +0x457
testing.(*M).Run(0xc000094320)
        C:/Program Files/Go/src/testing/testing.go:1719 +0x5d9
main.main()
        _testmain.go:57 +0x1aa
rax     0x20
rbx     0x110000
rcx     0xc000494270
rdi     0x1100000012
rsi     0xc0002de820
rbp     0xc00095dba8
rsp     0xc00095dad8
r8      0x23280
r9      0x8
r10     0x90
r11     0x0
r14     0xc000966600
r15     0xc004a90000
rip     0x0
rflags  0x10202
cs      0x33
fs      0x53
gs      0x2b
exit status 2

That issue is ONLY affecst JIT, so I think it’s an Wazero issue. The biggest issue is that it crashes the entire program and it’s not possible to recover.

Change:

wazero.NewRuntimeConfigJIT().WithFinishedFeatures()

To:

wazero.NewRuntimeConfigInterpreter().WithFinishedFeatures()

Runs the tests without issue:

=== RUN   TestEncodeObjectAPI
--- PASS: TestEncodeObjectAPI (17.07s)

Also, it’s ONLY affects WASM compiled with zig build install -Dtarget="wasm32-wasi" -Drelease-safe, so if you compile as debug zig build install -Dtarget="wasm32-wasi" it will run. A lot slower, but runs. The debug have more bounds checks and so on. So, maybe there’s something in my code that is actually crashing the runtime, crashing at one unrecoverable point.

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I’ll share the source-code soon.