Do not modify input in-place
SortedUniqueStrings and FirstUniqueStrings dedupes repeating elements
and returns the deduped list. Currently, it also modifies the input list
in-place, which causes non-determinisitc failures like b/275313114
Operate on a copy of the input so that the input remains untouched.
SortedUniqueStrings is O(NlogN) and FirstUniqueStrings is ~O(N), so
creating a copy (O(N)) should not result in major performance regressions.
Numbers for this single unit test:
```
go test . -run TestStubsForLibraryInMultipleApexes -v -count 1000
Before: 174s
After: 172s
```
Test: go test ./android
Test: go test . -run TestStubsForLibraryInMultipleApexes -v -count 1000
Change-Id: Id859723b2c2ebdc0023876c4b6fabe75d870bad7
diff --git a/android/util.go b/android/util.go
index 38e0a4d..fb09128 100644
--- a/android/util.go
+++ b/android/util.go
@@ -276,6 +276,8 @@
// FirstUniqueStrings returns all unique elements of a slice of strings, keeping the first copy of
// each. It modifies the slice contents in place, and returns a subslice of the original slice.
func FirstUniqueStrings(list []string) []string {
+ // Do not moodify the input in-place, operate on a copy instead.
+ list = CopyOf(list)
// 128 was chosen based on BenchmarkFirstUniqueStrings results.
if len(list) > 128 {
return firstUniqueStringsMap(list)
@@ -332,6 +334,7 @@
// SortedUniqueStrings returns what the name says
func SortedUniqueStrings(list []string) []string {
+ // FirstUniqueStrings creates a copy of `list`, so the input remains untouched.
unique := FirstUniqueStrings(list)
sort.Strings(unique)
return unique