[dev.fuzz] testing,internal/fuzz: prevent unbounded memory growth

Usage of f.testContext.match.fullName to generate the test name causes
unbounded memory growth, eventually causing the fuzzer to slow down
as memory pressure increases.

Each time fuzzFn is invoked it generates a unique string and stores it
in a map. With the fuzzer running at around 100k executions per second
this consumed around ~30GB of memory in a handful of minutes.

Instead just use the base name of the test for mutated inputs, a special
name for seeded inputs, and the filename for inputs from the input
corpus.

Change-Id: I083f47df7e82f0c6b0bda244f158233784a13029
Reviewed-on: https://go-review.googlesource.com/c/go/+/316030
Trust: Roland Shoemaker <roland@golang.org>
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>

diff --git a/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt b/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt
index 76e7907bf1cd46663eb37fba5f4c2871ffda1ff7..ca2b389321d782b786fb0f2ce37493f6affc6f8b 100644 (file)
--- a/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_mutate_crash.txt
@@ -21,6 +21,8 @@ go run check_testdata.go FuzzWithBug
 # Now, the failing bytes should have been added to the seed corpus for
 # the target, and should fail when run without fuzzing.
 ! go test
+stdout 'testdata[/\\]corpus[/\\]FuzzWithBug[/\\][a-f0-9]{64}'
+stdout 'this input caused a crash!'
 
 ! go test -run=FuzzWithNilPanic -fuzz=FuzzWithNilPanic -fuzztime=100x
 stdout 'testdata[/\\]corpus[/\\]FuzzWithNilPanic[/\\]'

diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index 3511cf41a6b5992673b2d67b79a3fdd68a10781a..a370bc9ac98a064c6a07e14f5b23363668bc0ced 100644 (file)
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -501,7 +501,7 @@ var depsRules = `
        FMT, flag, runtime/debug, runtime/trace, internal/sysinfo
        < testing;
 
-       FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token, math/rand
+       FMT, crypto/sha256, encoding/json, go/ast, go/parser, go/token, math/rand, encoding/hex, crypto/sha256
        < internal/fuzz;
 
        internal/fuzz, internal/testlog, runtime/pprof, regexp

diff --git a/src/internal/fuzz/fuzz.go b/src/internal/fuzz/fuzz.go
index b9d2d4cd5fb06bccff08578a05259c903f3a810f..d0545bd076d1e7d35cf47372466dac963e45b784 100644 (file)
--- a/src/internal/fuzz/fuzz.go
+++ b/src/internal/fuzz/fuzz.go
@@ -512,7 +512,7 @@ func ReadCorpus(dir string, types []reflect.Type) ([]CorpusEntry, error) {
                        errs = append(errs, fmt.Errorf("%q: %v", filename, err))
                        continue
                }
-               corpus = append(corpus, CorpusEntry{Name: file.Name(), Data: data, Values: vals})
+               corpus = append(corpus, CorpusEntry{Name: filename, Data: data, Values: vals})
        }
        if len(errs) > 0 {
                return corpus, &MalformedCorpusError{errs: errs}

diff --git a/src/testing/fuzz.go b/src/testing/fuzz.go
index 70e1b414a8b428fc8db93f757f20e62f6fb2ffc4..7afd24d2582c7afbca5576cd33a6766b1e83f159 100644 (file)
--- a/src/testing/fuzz.go
+++ b/src/testing/fuzz.go
@@ -226,7 +226,7 @@ func (f *F) Add(args ...interface{}) {
                }
                values = append(values, args[i])
        }
-       f.corpus = append(f.corpus, corpusEntry{Values: values})
+       f.corpus = append(f.corpus, corpusEntry{Values: values, Name: fmt.Sprintf("seed#%d", len(f.corpus))})
 }
 
 // supportedTypes represents all of the supported types which can be fuzzed.
@@ -298,21 +298,19 @@ func (f *F) Fuzz(ff interface{}) {
        // fn is called in its own goroutine.
        //
        // TODO(jayconrod,katiehockman): dedupe testdata corpus with entries from f.Add
-       // TODO(jayconrod,katiehockman): improve output when running the subtest.
-       // e.g. instead of
-       //    --- FAIL: FuzzSomethingError/#00 (0.00s)
-       // do
-       //    --- FAIL: FuzzSomethingError/<hash> (0.00s)
        run := func(e corpusEntry) error {
                if e.Values == nil {
                        // Every code path should have already unmarshaled Data into Values.
                        // It's our fault if it didn't.
                        panic(fmt.Sprintf("corpus file %q was not unmarshaled", e.Name))
                }
-               testName, ok, _ := f.testContext.match.fullName(&f.common, e.Name)
-               if !ok || shouldFailFast() {
+               if shouldFailFast() {
                        return nil
                }
+               testName := f.common.name
+               if e.Name != "" {
+                       testName = fmt.Sprintf("%s/%s", testName, e.Name)
+               }
                // Record the stack trace at the point of this call so that if the subtest
                // function - which runs in a separate stack - is marked as a helper, we can
                // continue walking the stack into the parent test.