Bug 6878 – Mutable result for toStringz()

In some situations you have to call C functions that accept a char* (not const). For simplify such usage cases I'd like std.string.toStringz to be closer to this: import core.stdc.string; char* toStringz(immutable(char[]) s) pure nothrow in { // The assert below contradicts the unittests! //assert(memchr(s.ptr, 0, s.length) == null, //text(s.length, ": `", s, "'")); } out (result) { if (result) { auto slen = s.length; while (slen > 0 && s[slen-1] == 0) --slen; assert(strlen(result) == slen); assert(memcmp(result, s.ptr, slen) == 0); // overkill? } } body { /+ Unfortunately, this isn't reliable. We could make this work if string literals are put in read-only memory and we test if s[] is pointing into that. /* Peek past end of s[], if it's 0, no conversion necessary. * Note that the compiler will put a 0 past the end of static * strings, and the storage allocator will put a 0 past the end * of newly allocated char[]'s. */ char* p = &s[0] + s.length; if (*p == 0) return s; +/ // Need to make a copy auto copy = new char[s.length + 1]; copy[0 .. s.length] = s[]; copy[s.length] = '\0'; return copy.ptr; } void main() { string t = "hello"; char* s1 = toStringz(t); const(char*) s2 = toStringz(t); immutable(char*) s3 = toStringz(t); immutable(char)* s4 = toStringz(t); }

Use std.utf.toUTFz. It allows you to get a pointer to whatever zero-terminate string type you want (both in terms of character type and constness). toStringz is simplified function for the common use case. We're not going to complicate it further. toUTFz gives you the functionality that you're looking for.