Re: string hashing design/implementation questions involving string literals

tragomaskhalos <>
Tue, 12 Feb 2008 11:41:38 -0800 (PST)
On 12 Feb, 13:30, Sebastian Karlsson <>
[ snip ]

If above is true there's still a very large problem remaining, users
passing strings that aren't string literals, for example
std::string::c_str() comes to mind. These aren't guaranteed to be
constant between calls to a StringHash constructor so I can't use the
memory address as a key to the value. I could create a constructor of
StringHash which accepts a std::string&, however that certainly
doesn't guarantee that the user doesn't use c_str(), and std::string
isn't really the only possible problem anyway. What really would help
me here would be if there's any neat way to guarantee that the client
only uses string literals for my StringHash( const char* )
constructor. Is there any?

Any feedback appreciated!

Firstly, I don't think there is any way to enforce string
literals. One might be tempted to defeat passing a char*
via eg
  template<int N> void bar(const char(&ca)[N]) { ...}
This will accept
but reject e.g.
The problem is it _also_ accepts
  char oh_dear[] = "In trouble now";
Where oh_dear may eg be on the stack.

But I think the problem is this: you've gone down
a rat-hole looking for a solution without looking
properly at the problem, because what actual use
  bar("magically works only with literals"); ??

When the string has to be hard-coded in, you
may as well just do this:
  void bar(int tag) { .... }

so that the user can just do this:
  enum my_tags {
    wow, yowza, hooray

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