[scudo][standalone] Get statistics in a char buffer

Summary:
Following up on D68471, this CL introduces some `getStats` APIs to
gather statistics in char buffers (`ScopedString` really) instead of
printing them out right away. Ultimately `printStats` will just
output the buffer, but that allows us to potentially do some work
on the intermediate buffer, and can be used for a `mallocz` type
of functionality. This allows us to pretty much get rid of all the
`Printf` calls around, but I am keeping the function in for
debugging purposes.

This changes the existing tests to use the new APIs when required.

I will add new tests as suggested in D68471 in another CL.

Reviewers: morehouse, hctim, vitalybuka, eugenis, cferris

Reviewed By: morehouse

Subscribers: delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D68653

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@374173 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/scudo/standalone/size_class_map.h b/lib/scudo/standalone/size_class_map.h
index 3b494afb3..dfef0865b 100644
--- a/lib/scudo/standalone/size_class_map.h
+++ b/lib/scudo/standalone/size_class_map.h
@@ -86,6 +86,7 @@ public:
   }
 
   static void print() {
+    ScopedString Buffer(1024);
     uptr PrevS = 0;
     uptr TotalCached = 0;
     for (uptr I = 0; I < NumClasses; I++) {
@@ -93,19 +94,20 @@ public:
         continue;
       const uptr S = getSizeByClassId(I);
       if (S >= MidSize / 2 && (S & (S - 1)) == 0)
-        Printf("\n");
+        Buffer.append("\n");
       const uptr D = S - PrevS;
       const uptr P = PrevS ? (D * 100 / PrevS) : 0;
       const uptr L = S ? getMostSignificantSetBitIndex(S) : 0;
       const uptr Cached = getMaxCachedHint(S) * S;
-      Printf(
+      Buffer.append(
           "C%02zu => S: %zu diff: +%zu %02zu%% L %zu Cached: %zu %zu; id %zu\n",
           I, getSizeByClassId(I), D, P, L, getMaxCachedHint(S), Cached,
           getClassIdBySize(S));
       TotalCached += Cached;
       PrevS = S;
     }
-    Printf("Total Cached: %zu\n", TotalCached);
+    Buffer.append("Total Cached: %zu\n", TotalCached);
+    Buffer.output();
   }
 
   static void validate() {