Closed
Description
Coverage uses inserted global variable in the code to track coverage. When this is combined with the race checks it can lead to erroneous and very confusing race conditions.
The following site presents some simple code when run with the "-race" flag added and in coverage mode will give the false erroneous race conditions.
http://herman.asia/running-the-go-race-detector-with-cover
Package:
package coverrace
func add100() int {
total := 0
c := make(chan int, 1)
for i := 0; i < 100; i++ {
go func(chan int) {
c <- 1
}(c)
}
for u := 0; u < 100; u++ {
total += <-c
}
return total
}Test:
package coverrace
import "testing"
func TestCoverRace(t *testing.T) {
got := add100()
if got != 100 {
t.Errorf("got %d, want %d", got, 100)
}
}Reproducing command generated by PyCharm:
go test -v -race ./... -coverprofile=/someUserDir/coverrace$All_in__coverrace_.coverage -covermode=countThis has been fixed in go > 1.3+ by adding support for the '-covermode=atomic' flag. This ensures that the access to the coverage global variable is protected by the sync package to avoid race detection.