[scudo] Improve Secondary Cache Dump

[frs513]

Summary

Exclude cached blocks with invalid start address. Mainly concerned with
cached blocks that are still available/unused.

[cferris]

compiler-rt/lib/scudo/standalone/secondary.h

176

I think you need to rebase, this should not be listed as a change.

[Chia-hungDuan]

compiler-rt/lib/scudo/standalone/secondary.h

146–148

Nit: Single line statement doesn't need braces

https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

[frs513]

rebased and got rid of brackets for single line statement

[cferris]

LGTM, but you misspelled concern in your commit message.

[frs513]

fixed grammar in commit message

[Chia-hungDuan]

I'll merge this change

compiler-rt/lib/scudo/standalone/secondary.h

public:
 
   void getStats(ScopedString *Str) {
     ScopedLock L(Mutex);
     Str->append("Stats: MapAllocatorCache: EntriesCount: %d, "
                 "MaxEntriesCount: %u, MaxEntrySize: %zu\n",
                 EntriesCount, atomic_load_relaxed(&MaxEntriesCount),
                 atomic_load_relaxed(&MaxEntrySize));
     for (CachedBlock Entry : Entries) {
+      if (!Entry.CommitBase)
+        continue;
       Str->append("StartBlockAddress: 0x%zx, EndBlockAddress: 0x%zx, "
                   "BlockSize: %zu\n",
-                  Entry.CommitBase, (Entry.CommitBase + Entry.CommitSize),
+                  Entry.CommitBase, Entry.CommitBase + Entry.CommitSize,
                   Entry.CommitSize);
     }
   }
 
   // Ensure the default maximum specified fits the array.
   static_assert(CacheConfig::DefaultMaxEntriesCount <=
                     CacheConfig::EntriesArraySize,
                 "");
public:
 
   void store(Options Options, LargeBlock::Header *H) EXCLUDES(Mutex) {
     if (!canCache(H->CommitSize))
       return unmap(H);
 
     bool EntryCached = false;
     bool EmptyCache = false;
     const s32 Interval = atomic_load_relaxed(&ReleaseToOsIntervalMs);
     const u64 Time = getMonotonicTimeFast();
     const u32 MaxCount = atomic_load_relaxed(&MaxEntriesCount);
     CachedBlock Entry;
     Entry.CommitBase = H->CommitBase;
     Entry.CommitSize = H->CommitSize;
     Entry.BlockBegin = reinterpret_cast<uptr>(H + 1);
     Entry.MemMap = H->MemMap;
     Entry.Time = Time;
     if (useMemoryTagging<Config>(Options)) {