diff options
Diffstat (limited to 'src/runtime')
| -rw-r--r-- | src/runtime/slice.go | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/src/runtime/slice.go b/src/runtime/slice.go index 228697a708..29e2fd5cbd 100644 --- a/src/runtime/slice.go +++ b/src/runtime/slice.go @@ -186,14 +186,21 @@ func growslice(oldPtr unsafe.Pointer, newLen, oldCap, num int, et *_type) slice if oldCap < threshold { newcap = doublecap } else { - // Check 0 < newcap to detect overflow - // and prevent an infinite loop. - for 0 < newcap && newcap < newLen { + for { // Transition from growing 2x for small slices // to growing 1.25x for large slices. This formula // gives a smooth-ish transition between the two. - newcap += (newcap + 3*threshold) / 4 + newcap += (newcap + 3*threshold) >> 2 + + // We need to check `newcap >= newLen` and whether `newcap` overflowed. + // newLen is guaranteed to be larger than zero, hence + // when newcap overflows then `uint(newcap) > uint(newLen)`. + // This allows to check for both with the same comparison. + if uint(newcap) >= uint(newLen) { + break + } } + // Set newcap to the requested cap when // the newcap calculation overflowed. if newcap <= 0 { |