[wasm2wat] Incorrect rejection of valid module

[pventuzelo]

Hi,

During fuzzing I found that the following module was consider invalid by wabt due to a leb128 parsing error. Binaryen choose to "reject" this module but precise that it is a valid module. Other tools like wasmer, wasmtime and wasm-tools valid this module.

Reproducing

Download:
reject_leb128_wabt.zip

WABT:

$ ./wasm-validate reject_leb128_wabt.wasm 
0000016: error: unable to read u32 leb128: table_size

Other tools:

# binaryen
$ wasm-opt reject_leb128_wabt.wasm
wasm-opt reject_leb128_wabt2.wasm
[parse exception: inline string contains NULL (0). that is technically valid in wasm, but you shouldn't do it, and it's not supported in binaryen (at 0:34)]
Fatal: error parsing wasm
# wasmer
$ wasmer validate reject_leb128_wabt2.wasm
# wasm-tools
$ ./wasm-tools/target/debug/wasm-validate-rs reject_leb128_wabt.wasm
$ ./wasm-tools/target/debug/wasm2wat-rs reject_leb128_wabt.wasm
(module
  (type (;0;) (func (param i32 i32 f64)))
  (type (;1;) (func (param i32 i32) (result f64)))
  (type (;2;) (func (param i32 i32)))
  (type (;3;) (func (result f64)))
  (type (;4;) (func (param i32) (result f64)))
  (type (;5;) (func))
  (import "env" "memoryBase" (global (;0;) i32))
  (import "env" "memory" (memory (;0;) 0 2))
  (import "e`v" "table" (table (;0;) 0 funcref))
  (import "^^v" "tableBase" (global (;1;) i32))
)

Branch: master
commit: 15264cd

[binji]

This is an "error" because the custom dynlink section is malformed. wasm-validate currently fails in this case, but will just produce only a warning if run with --ignore-custom-section-errors. Perhaps this is the wrong default? @sbc100 wdyt?

[sbc100]

Perhaps we should make it clear when the error is from a custom section? And point users to --ignore-custom-section-errors in the error message?

Also, perhaps that flag is misnamed, since "ignore" and "only-warn" are two different things, no?