A safer interface for core.stdc

[Andrei Alexandrescu via Digitalmars-d]

On 2/7/15 5:26 PM, H. S. Teoh via Digitalmars-d wrote:
> On Sun, Feb 08, 2015 at 12:39:39AM +0000, bearophile via Digitalmars-d wrote:
>> Andrei Alexandrescu:
>>
>>> Such wrappers would allow safe code to use more C stdlib primitives.
>>
>> I'd also like a safer templated wrapper for calloc() and malloc() and
>> similar.
> [...]
>
> You mean something like this?
>
> 	T* malloc(T)() @trusted
> 	{
> 		return cast(T*)malloc(T.sizeof);
> 	}

I think that would go as follows:

private @system T[] mallocUninitializedArrayImpl(T)(size_t n)
{
     auto p = malloc(n * T.sizeof);
     p || assert(0, "Not enough memory");
     return (cast(T*) p)[0 .. n];
}

@trusted T[] mallocUninitializedArray(size_t n)
if (!hasIndirections!T)
{
     return mallocUninitializedArrayImpl!T(n);
}

@system T[] mallocUninitializedArray(size_t n)
if (hasIndirections!T)
{
     return mallocUninitializedArrayImpl!T(n);
}

Similarly there'd be a mallocMinimallyInitializedArray that zeroes only 
pointers and is @trusted for all types.

Then we'd probably have a @trusted callocArray that blasts zeros 
throughout. It's @trusted because we know pointers are zeroes (an 
assumption somewhat not robust in theory but fine in practice).

Then we'd have a mallocArray that allocates an array and initializes 
each element with .init.

> 	struct MyStruct {
> 		int x, y, z;
> 	}
>
> 	void main() {
> 		auto p = malloc!MyStruct();
>
> 		// Not sure how to make free() usable from @safe, unless
> 		// we wrap the pointer returned by malloc().
> 		free(p);
> 	}

Indeed we have no safe way to wrap free.


Andrei