On Monday, 13 May 2013 at 07:13:03 UTC, maarten van damme wrote:
But seeing as the memory only starts growing when I put the png
line in
This is pretty strange because looking at the source there, the
only time data is even referenced is here:
output ~= data[pos..pos+bytesPerLine];
Which makes a copy. There's no delegates or anything so shouldn't
be a copied stack reference sticking around.... I see no reason
why this wouldn't work.
I also tried replacing the new ubyte with malloc/free hoping it'd
get an access violation if it was used after free, and nothing
came up.
But my computer that i'm using right now is one of those netbooks
so it doesn't have the cpu power to generate hte large images. I
did a 200x100 instead which obviously uses way less memory. But
still, if it was a bad reference I think it would show up here
too.
The only other line that might be a problem is this one:
auto com = cast(ubyte[]) compress(output);
output is at this point a copy of data, with other things added.
So it'd be a very large array too.... and is created through the
~= operator, so it is all gc managed. Could be a false positive
pointing into this array causing the leak.
And the compress function, from std.zlib, does this:
auto destlen = srcbuf.length + ((srcbuf.length + 1023) /
1024) + 12;
auto destbuf = new ubyte[destlen];
auto err = etc.c.zlib.compress2(destbuf.ptr, &destlen,
cast(ubyte *)srcbuf.ptr, srcbuf.length, level);
if (err)
{ delete destbuf;
throw new ZlibException(err);
}
destbuf.length = destlen;
Which is again, destbuf being another large gc managed array. So
my guess is either my output or std.zlib's destbuf is getting
mistaken for still being referenced by some random number on the
stack, so the gc is conservatively keeping it around.
A potential fix would be for my png.d to manually manage this
memory - preallocate output[] with malloc and perhaps use its own
compress function with its own manual buffer too. I figure this
would be a new function, savePngFromImage, that saves the file
itself instead of returning the array so it has complete control
over the reference.
