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[dev.fuzz] internal/fuzz: allow setting pcg seed via GODEBUG 

Format is "fuzzseed=123".

Change-Id: Idb314270c8fd4307149c8503e13424b653ec4b0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/313651
Trust: Roland Shoemaker <roland@golang.org>
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
This commit is contained in:
Roland Shoemaker 2021-04-26 13:00:15 -07:00
parent 7a7eee8ab7
commit 0b5470f31d
1 changed files with 20 additions and 0 deletions
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20
src/internal/fuzz/pcg.go
View File

@ -6,6 +6,9 @@ package fuzz
import (
"math/bits"
"os"
"strconv"
"strings"
"sync/atomic"
"time"
)
@ -28,10 +31,27 @@ type pcgRand struct {
inc uint64
}
func godebugSeed() *int {
debug := strings.Split(os.Getenv("GODEBUG"), ",")
for _, f := range debug {
if strings.HasPrefix(f, "fuzzseed=") {
seed, err := strconv.Atoi(strings.TrimPrefix(f, "fuzzseed="))
if err != nil {
panic("malformed fuzzseed")
}
return &seed
}
}
return nil
}
// newPcgRand generates a new, seeded Rand, ready for use.
func newPcgRand() *pcgRand {
r := new(pcgRand)
now := uint64(time.Now().UnixNano())
if seed := godebugSeed(); seed != nil {
now = uint64(*seed)
}
inc := atomic.AddUint64(&globalInc, 1)
r.state = now
r.inc = (inc << 1) | 1