fmt: make the malloc test check its counts

Discover than %g is now down to 1 malloc from 2 from 4.
Have fun with funcs.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5504077

diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index d7fe296f09575ef384b826c82ce1cfacade2f377..d34a4f8fd2d368c2ce81f4497d26ee69be6c4d45 100644 (file)
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -506,78 +506,42 @@ func BenchmarkSprintfFloat(b *testing.B) {
        }
 }
 
+var mallocBuf bytes.Buffer
+
+var mallocTest = []struct {
+       count int
+       desc  string
+       fn    func()
+}{
+       {0, `Sprintf("")`, func() { Sprintf("") }},
+       {1, `Sprintf("xxx")`, func() { Sprintf("xxx") }},
+       {1, `Sprintf("%x")`, func() { Sprintf("%x", 7) }},
+       {2, `Sprintf("%s")`, func() { Sprintf("%s", "hello") }},
+       {1, `Sprintf("%x %x")`, func() { Sprintf("%x", 7, 112) }},
+       {1, `Sprintf("%g")`, func() { Sprintf("%g", 3.14159) }},
+       {0, `Fprintf(buf, "%x %x %x")`, func() { mallocBuf.Reset(); Fprintf(&mallocBuf, "%x %x %x", 7, 8, 9) }},
+       {1, `Fprintf(buf, "%s")`, func() { mallocBuf.Reset(); Fprintf(&mallocBuf, "%s", "hello") }},
+}
+
+var _ bytes.Buffer
+
 func TestCountMallocs(t *testing.T) {
        if testing.Short() {
                return
        }
-       const N = 100
-       runtime.UpdateMemStats()
-       mallocs := 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               Sprintf("")
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Sprintf(\"\"): %d\n", mallocs/N)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               Sprintf("xxx")
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Sprintf(\"xxx\"): %d\n", mallocs/N)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               Sprintf("%x", i)
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Sprintf(\"%%x\"): %d\n", mallocs/N)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               Sprintf("%s", "hello")
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Sprintf(\"%%s\"): %d\n", mallocs/N)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               Sprintf("%x %x", i, i)
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Sprintf(\"%%x %%x\"): %d\n", mallocs/N)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               Sprintf("%g", 3.14159)
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Sprintf(\"%%g\"): %d\n", mallocs/N)
-       buf := new(bytes.Buffer)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               buf.Reset()
-               Fprintf(buf, "%x %x %x", i, i, i)
-       }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Fprintf(buf, \"%%x %%x %%x\"): %d\n", mallocs/N)
-       runtime.UpdateMemStats()
-       mallocs = 0 - runtime.MemStats.Mallocs
-       for i := 0; i < N; i++ {
-               buf.Reset()
-               Fprintf(buf, "%s", "hello")
+       for _, mt := range mallocTest {
+               const N = 100
+               runtime.UpdateMemStats()
+               mallocs := 0 - runtime.MemStats.Mallocs
+               for i := 0; i < N; i++ {
+                       mt.fn()
+               }
+               runtime.UpdateMemStats()
+               mallocs += runtime.MemStats.Mallocs
+               if mallocs/N != uint64(mt.count) {
+                       t.Errorf("%s: expected %d mallocs, got %d", mt.desc, mt.count, mallocs/N)
+               }
        }
-       runtime.UpdateMemStats()
-       mallocs += runtime.MemStats.Mallocs
-       Printf("mallocs per Fprintf(buf, \"%%s\"): %d\n", mallocs/N)
 }
 
 type flagPrinter struct{}