Fix unused result errors in bionic.

This lets us use _FORTIFY_SOURCE=2 on the host.

Change-Id: I69f5ff9834bfd595aae6584104bee10c4d8a5eeb

benchmarks/stdio_benchmark.cpp

@@ -16,6 +16,7 @@
 
 #include <stdio.h>
 #include <stdio_ext.h>
+#include <stdlib.h>
 
 #include <benchmark/Benchmark.h>
 
@@ -73,7 +74,7 @@ static void FopenFgetsFclose(int iters, bool no_locking) {
   for (int i = 0; i < iters; ++i) {
     FILE* fp = fopen("/proc/version", "re");
     if (no_locking) __fsetlocking(fp, FSETLOCKING_BYCALLER);
-    fgets(buf, sizeof(buf), fp);
+    if (fgets(buf, sizeof(buf), fp) == nullptr) abort();
     fclose(fp);
   }
 }

benchmarks/utils.cpp

@@ -14,14 +14,16 @@
  * limitations under the License.
  */
 
+#include "utils.h"
+
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
 
 #include <string>
 
-#include "utils.h"
+#include <base/stringprintf.h>
 
 int Round(int n) {
   int base = 1;
@@ -72,10 +74,7 @@ std::string PrettyInt(long value, size_t base) {
       break;
     }
   }
-  char* s = NULL;
-  asprintf(&s, "%s%" PRId64 "%s", (negative_number ? "-" : ""),
-           count / kAmountPerUnit[i], kUnitStrings[i]);
-  std::string result(s);
-  free(s);
-  return result;
+  return android::base::StringPrintf("%s%" PRId64 "%s",
+                                     negative_number ? "-" : "",
+                                     count / kAmountPerUnit[i], kUnitStrings[i]);
 }