Does dynamic array literal, which is NOT created by make proc, must be deleted using delete proc?
darr1 := make([dynamic]int, 5)
delete(darr1) // Dynamic array made with `make` must be deleted.
darr2: [dynamic]int
delete(darr2) // How about this case? Does commenting this line cause a memory leak?
It might be a dumb question, but I’m asking it here because I couldn’t find example code that mentions about it.
The latter won’t allocate anything on its own, the [dynamic]int is just zeroed (nil pointer/0 length/0 capacity/no allocator). But as soon as some space is needed (e.g. from append, resize, or reserve), then it’ll allocate, after which it would need to be deleted to avoid leaking its memory.
make([dynamic]int), without a length or capacity, is actually similar. It sets the allocator that will be used when it allocates, but doesn’t immediately allocate anything.
If you want to see what’s happening internally, you can transmute it to runtime.Raw_Dynamic_Array:
darr: [dynamic]int
fmt.println(transmute(runtime.Raw_Dynamic_Array)darr)
// Raw_Dynamic_Array{data = 0x0, len = 0, cap = 0, allocator = Allocator{procedure = nil, data = 0x0}}
// data pointer is nil, so there's no allocation
append(&darr, 1, 2, 3)
fmt.println(transmute(runtime.Raw_Dynamic_Array)darr)
// Raw_Dynamic_Array{data = 0x17384018, len = 3, cap = 8, allocator = Allocator{procedure = proc(rawptr, Allocator_Mode, int, int, rawptr, int, Source_Code_Location) -> ([]u8, Allocator_Error) @ 0x43ECB0, data = 0x0}}
// data pointer has been set, the dynamic array has allocated
// the allocator has also been set to context.allocator since it wasn't specified
delete(darr)
fmt.println(transmute(runtime.Raw_Dynamic_Array)darr)
// Raw_Dynamic_Array{data = 0x17384018, len = 3, cap = 8, allocator = Allocator{procedure = proc(rawptr, Allocator_Mode, int, int, rawptr, int, Source_Code_Location) -> ([]u8, Allocator_Error) @ 0x43ECB0, data = 0x0}}
// note that the pointer is still set--it's no longer valid and shouldn't be used again without resetting the dynamic array (e.g. darr = {})
// of particular note, don't delete a dynamic array before you return it from a proc!
That will only define a variable, but will not allocate memory, as mentioned by Barinzaya.
You can use tracking-allocator to test ideas like that. Also a good idea in general to have as part of your project as you test code to make sure memory is managed.
Karl’s tracker here.
I also have a fancy colorized version of a tracker here.