md5 hashing acting strangly?

[bearophile via Digitalmars-d-learn]

Sean Campbell:

> i have the following code
> char[] Etag(string file){
> 	auto info = DirEntry(file);
> 	ubyte[16] hash = md5Of(to!string(info.timeLastAccessed.day)~
> 	                       to!string(info.timeLastAccessed.month)~
> 	                       to!string(~info.timeLastAccessed.year)~
> 	                       file);
> 	char[] hashstring = toHexString(hash);
> 	writeln(hashstring);
> 	return hashstring;
> }
> the proper hash string prints out in the console, but when i 
> try to use the return value of Etag it becomes an obscure 
> string?

As shown in the docs toHexString returns a fixed size array, that 
in D are values. With "char[] hashstring = " you are slicing a 
stack allocated variable, so Etag returns garbage. So you can 
write (note the starting lowercase):

auto etag(string file) {
...
> 	auto hashstring = toHexString(hash);
> 	writeln(hashstring);
> 	return hashstring;
> }

Such kind of bugs are impossible in Rust. Hopefully we'll 
eventually remove them from D too.

Bye,
bearophile