Huge allocation leaks are detected correctly.
Tiny allocation leaks are problematic, both false positive and false negative.
For example:
leaks Report Version: 2.0
Process 73345: 4980 nodes malloced for 1677 KB
Process 73345: 1 leak for 1048576 total leaked bytes.
Leak: 0x10aed0000 size=1048576 zone: SwiftZone_0x10adc35d8
Swift SVN r18007