reset []bytes after getting them from sync.Pool

.circleci/config.yml

@@ -156,7 +156,7 @@ jobs:
                 if [ "$CIRCLE_BRANCH" == "master" ]; then
                     printf "\n $CIRCLE_BRANCH branch, ignoring check for relese notes \n"
                 else
-                    ChangedFiles=`git diff --name-only $CIRCLE_BRANCH origin/master`
+                    ChangedFiles=`git diff --name-only origin/master`
                     case "$ChangedFiles" in
                         *RELEASE_NOTES.*)
                             printf "\n Thanks, your commits include update to release notes. \n";;

.github/RELEASE_NOTES.md

@@ -8,6 +8,7 @@
 - removed vendor directory and dep files: https://github.com/komuw/meli/pull/107
 - we no longer release meli for 386 arch on github releases.  
   We now ONLY release amd64 for darwin, linux and windows
+- Fixed a bug where buffers from sync.Pool were not reset before use: https://github.com/komuw/meli/pull/119
 
 
 ## v0.1.9.8

image.go

@@ -116,6 +116,12 @@ var blackHolePool = sync.Pool{
 // this is taken from io.util
 func poolReadFrom(r io.Reader) (n int64, err error) {
 	bufp := blackHolePool.Get().(*[]byte)
+	// reset the buffer since it may contain data from a previous round
+	// see issues/118
+	for i := range *bufp {
+		(*bufp)[i] = 0
+
+	}
 	readSize := 0
 	for {
 		readSize, err = r.Read(*bufp)

image_test.go

@@ -3,6 +3,7 @@ package meli
 import (
 	"context"
 	"io/ioutil"
+	"strings"
 	"testing"
 )
 
@@ -91,3 +92,14 @@ func BenchmarkBuildDockerImage(b *testing.B) {
 		_, _ = BuildDockerImage(ctx, cli, dc)
 	}
 }
+
+func BenchmarkPoolReadFrom(b *testing.B) {
+	// go test -run=XXX -bench=BenchmarkPoolReadFrom
+	// BenchmarkPoolReadFrom-4   	30000000	        36.0 ns/op
+	// after fixing issues/118:                         50.1 ns/op
+	r := strings.NewReader("hello")
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		_, _ = poolReadFrom(r)
+	}
+}