When is memory allocated by malloc garbage collected?

Question

I am guessing (hoping) the answer is never. That such memory must be explicitly freed.

For example if if I wrote:

julia> x = Libc.malloc(1_000_000)
Ptr{Void} @0x0000000002f6bd80

julia> x = nothing

have I just leaked ~1MB of memory?

However I am not 100% certain this is true, because the docs don't mention it at all.

help?> Libc.malloc(3)
malloc(size::Integer) -> Ptr{Void}

Call malloc from the C standard library.

Answer 1

Yes, you are correct.

Julia is designed to seamlessly interoperate with C on a low level, so when you use the C wrapper libraries, you you get C semantics and no garbage collection.

The docs for Libc.malloc is not written to teach C, but could be improved to mention Libc.free, in case anyone gets confused.