GC and slices

[Lionello Lunesu]

Walter Bright wrote:
> Oskar Linde wrote:
>> This is a very short question regarding the liberties of the GC. Is it 
>> safe to rely on data outside a slice?
> 
> Yes, because all a slice is is an interior pointer, and interior 
> pointers hold the entire allocated chunk.

Are you guys sure?!

I was using a void[] as a fifo queue, appending new items to the list 
with ~= and removing processed items with list = list[1..$] and was 
wondering if the memory at the beginning of the list.ptr was ever being 
freed, so I made this small test program:

#import std.stdio;
#long[] queue = [123,1234,1233,435,7654,54,3241];
#void main() {
#	const size_t MASK = 1024*1024*16-1;
#	size_t size;
#	while (1) {
#		queue ~= size;			// anything
#		size += long.sizeof;
#		long* t = queue.ptr;
#		queue = queue[1..$];
#		assert( queue[0] != 123 );	// popped?
#		assert( queue.length == 7 );	
#		assert( (t+1) == queue.ptr );	// moved?
#		if ((size&MASK) == 0)		// stats
#			writefln(size);
#	}
#}	

and it seems it IS being freed! The (virtual) memory is not growing!

How can this be? Is the GC smarter than we think?

L.