view dmd/lstring.h @ 1117:4c20fcc4252b

Fun with parameter attributes: For several of the "synthetic" parameters added to D functions, we can apply noalias and nocapture. They are sret parameters, 'nest' pointers passed to nested functions, and _argptr: Nocapture: - Sret and nest are nocapture because they don't represent D-level variables, and thus the callee can't (validly) obtain a pointer to them, let alone keep it around after it returns. - _argptr is nocapture because although the callee has access to it as a pointer, that pointer is invalidated when it returns. All three are noalias because they're function-local variables - Sret and _argptr are noalias because they're freshly alloca'd memory only used for a single function call that's not allowed to keep an aliasing pointer to it around (since the parameter is nocapture). - 'Nest' is noalias because the callee only ever has access to one such pointer per parent function, and every parent function has a different one. This commit also ensures attributes set on sret, _arguments and _argptr are propagated to calls to such functions. It also adds one exception to the general rule that attributes on function types should propagate to calls: the type of a delegate's function pointer has a 'nest' parameter, but this can either be a true 'nest' (for delegates to nested functions) or a 'this' (for delegates to member functions). Since 'this' is neither noalias nor nocapture, and there's generally no way to tell which one it is, we remove these attributes at the call site if the callee is a delegate.
author Frits van Bommel <fvbommel wxs.nl>
date Sat, 14 Mar 2009 22:15:31 +0100
parents c53b6e3fe49a
children
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// lstring.h
// length-prefixed strings

// Copyright (c) 1999-2002 by Digital Mars
// All Rights Reserved
// written by Walter Bright
// www.digitalmars.com
// License for redistribution is by either the Artistic License
// in artistic.txt, or the GNU General Public License in gnu.txt.
// See the included readme.txt for details.

#ifndef LSTRING_H
#define LSTRING_H 1

#include "dchar.h"

struct Lstring
{
    unsigned length;

    // Disable warning about nonstandard extension
    #pragma warning (disable : 4200)
    dchar string[];

    static Lstring zero;	// 0 length string

    // No constructors because we want to be able to statically
    // initialize Lstring's, and Lstrings are of variable size.

    #if M_UNICODE
    #define LSTRING(p,length) { length, L##p }
    #else
    #define LSTRING(p,length) { length, p }
    #endif

#if __GNUC__
    #define LSTRING_EMPTY() { 0 }
#else
    #define LSTRING_EMPTY() LSTRING("", 0)
#endif

    static Lstring *ctor(const dchar *p) { return ctor(p, Dchar::len(p)); }
    static Lstring *ctor(const dchar *p, unsigned length);
    static unsigned size(unsigned length) { return sizeof(Lstring) + (length + 1) * sizeof(dchar); }
    static Lstring *alloc(unsigned length);
    Lstring *clone();

    unsigned len() { return length; }

    dchar *toDchars() { return string; }

    hash_t hash() { return Dchar::calcHash(string, length); }
    hash_t ihash() { return Dchar::icalcHash(string, length); }

    static int cmp(const Lstring *s1, const Lstring *s2)
    {
	int c = s2->length - s1->length;
	return c ? c : Dchar::memcmp(s1->string, s2->string, s1->length);
    }

    static int icmp(const Lstring *s1, const Lstring *s2)
    {
	int c = s2->length - s1->length;
	return c ? c : Dchar::memicmp(s1->string, s2->string, s1->length);
    }

    Lstring *append(const Lstring *s);
    Lstring *substring(int start, int end);
};

#endif