stats: Avoid asserts in fuzz-tests by eliminating arbitrary length limits, using the new MemBlock wrapper for memcpy

test/common/stats/symbol_table_fuzz_test.cc

@@ -5,26 +5,42 @@
 #include "test/fuzz/fuzz_runner.h"
 #include "test/fuzz/utility.h"
 
+#include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
+
 namespace Envoy {
 namespace Stats {
 namespace Fuzz {
 
+// Adds a stat-name to the symbol table, discarding it if it ends in ".", and
+// splitting it in two if it's too long (64k bytes).
+//
+// The actual requirement for StatName allows up to 64k "."-separated segments
+// of 64k, but it's simpler to just limit the whole string. I don't think
+// there's that much value in using strings larger than 64k.
+void addSymbol(StatNamePool& pool, SymbolTable& symbol_table, absl::string_view str) {
+  while (absl::EndsWith(str, ".")) {
+    str.remove_suffix(1);
+  }
+
+  if (str.size() >= StatNameMaxSize) {
+    size_t halfway = str.size() / 2;
+    addSymbol(pool, symbol_table, str.substr(0, halfway));
+    addSymbol(pool, symbol_table, str.substr(halfway));
+  } else if (!str.empty()) {
+    StatName stat_name = pool.add(str);
+    FUZZ_ASSERT(str == symbol_table.toString(stat_name));
+  }
+}
+
 // Fuzzer for symbol tables.
 DEFINE_FUZZER(const uint8_t* buf, size_t len) {
   FuzzedDataProvider provider(buf, len);
   SymbolTableImpl symbol_table;
   StatNamePool pool(symbol_table);
 
   while (provider.remaining_bytes() != 0) {
-    std::string next_data = provider.ConsumeRandomLengthString(provider.remaining_bytes());
-
-    // ending with a "." is not considered legal, so just skip.
-    if (!next_data.empty() && next_data[next_data.size() - 1] == '.') {
-      continue;
-    }
-
-    StatName stat_name = pool.add(next_data);
-    FUZZ_ASSERT(next_data == symbol_table.toString(stat_name));
+    addSymbol(pool, symbol_table, provider.ConsumeRandomLengthString(provider.remaining_bytes()));
   }
 }