UTF8ToString fails on specific strings

[jeffRTC]

@sbc100 @kripken

This is a crazy one.

I pass Base64 strings like eyJuYW1lIjogIkphc29uIiwgImFnZSI6ICI0OCJ9 to JavaScript side.

Basically,

std::string text = "eyJuYW1lIjogIkphc29uIiwgImFnZSI6ICI0OCJ9";

// Call C-extern function
printSomething(text.c_str());

Now Javascript side try convert the pointer passed to JS function to UTF8 string using this way,

    printSomething: async function(pText) {
        let converted = UTF8ToString(pText);
        
        console.log(converted)
    }

But it returns an empty string as a result instead eyJuYW1lIjogIkphc29uIiwgImFnZSI6ICI0OCJ9.

I've ran the Javascript debugger over UTF8ToString and I find that it returns "\u0001" so for naked eye it's an empty string..

[jeffRTC]

I've ran dozens of texts to make sure this issue is not on my side. This doesn't happen with simple strings according to my tests.

"Hello World" 
"FooBar"
"Dan Rocks"
"www.google.com"

All got printed..

I'm using following flags when compiling

-Wall -Wextra -g2 -s ASSERTIONS=2 -s INITIAL_MEMORY=500MB -s ALLOW_MEMORY_GROWTH=1 
-fsanitize=address -fsanitize=undefined -s DEMANGLE_SUPPORT=1 -gseparate-dwarf 
-s DISABLE_EXCEPTION_CATCHING=0 -s ALLOW_TABLE_GROWTH=1 -std=gnu++17

Ubsan and Address Sanitizer is enabled and It didn't caught anything like heap after use etc

[jeffRTC]

Turns out, I'm using an invalidated pointer but for some reason the small strings got lucky. Fixed it by using a local copy inside class...

[sbc100]

Do async functions work at all in library JS files? What does that mean in that context?