runtime/coverage: avoid non-test coverage profiles in test report helper

When walking through the set of coverage data files generated from a
"go test -cover" run, it's possible to encounter pods (clumps of data
files) that were generated by a run from an instrumented Go tool (for
example, cmd/compile). Add a guard to the test reporting code to
ensure that it only processes files created by the currently running
test.

Fixes #57924.

Change-Id: I1bb7dce88305e1088162e3cb1df628486ecee1c1
Reviewed-on: https://go-review.googlesource.com/c/go/+/462756
Reviewed-by: David Chase <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Run-TryBot: Than McIntosh <[email protected]>

Author: thanm

src/runtime/coverage/testsupport.go

@@ -15,6 +15,7 @@ import (
 	"internal/coverage/pods"
 	"io"
 	"os"
+	"strings"
 )
 
 // processCoverTestDir is called (via a linknamed reference) from
@@ -80,7 +81,15 @@ func processCoverTestDirInternal(dir string, cfile string, cm string, cpkg strin
 		cf:    cformat.NewFormatter(cmode),
 		cmode: cmode,
 	}
+	// Generate the expected hash string based on the final meta-data
+	// hash for this test, then look only for pods that refer to that
+	// hash (just in case there are multiple instrumented executables
+	// in play). See issue #57924 for more on this.
+	hashstring := fmt.Sprintf("%x", finalHash)
 	for _, p := range podlist {
+		if !strings.Contains(p.MetaFile, hashstring) {
+			continue
+		}
 		if err := ts.processPod(p); err != nil {
 			return err
 		}