diff --git a/libc/src/stdio/printf_core/parser.h b/libc/src/stdio/printf_core/parser.h
--- a/libc/src/stdio/printf_core/parser.h
+++ b/libc/src/stdio/printf_core/parser.h
@@ -42,14 +42,23 @@
       return (size == other.size) && (primary_type == other.primary_type);
     }
   };
-  // TODO: Make this size configurable via a compile option.
-  static constexpr size_t DESC_ARR_LEN = 32;
+// This buffer is always initialized when printf is called. In cases where index
+// mode is necessary but memory is limited, or when index mode performance is
+// important and memory is available, this compile option provides a knob to
+// adjust memory usage to an appropriate level. 128 is picked as the default
+// size since that's big enough to handle even extreme cases and the runtime
+// penalty for not having enough space is severe.
+#ifndef LLVM_LIBC_PRINTF_INDEX_ARR_LEN
+  static constexpr size_t DESC_ARR_LEN = 128;
+#else
+  static constexpr size_t DESC_ARR_LEN = LLVM_LIBC_PRINTF_INDEX_ARR_LEN;
+#endif
   // desc_arr stores the sizes of the variables in the ArgList. This is used in
   // index mode to reduce repeated string parsing. The sizes are stored as
   // TypeDesc objects, which store the size as well as minimal type information.
   // This is necessary because some systems separate the floating point and
   // integer values in va_args.
-  TypeDesc desc_arr[DESC_ARR_LEN];
+  TypeDesc desc_arr[DESC_ARR_LEN] = {{0, Integer}};
 
   // TODO: Look into object stores for optimization.
 
@@ -58,10 +67,7 @@
 public:
 #ifndef LLVM_LIBC_PRINTF_DISABLE_INDEX_MODE
   Parser(const char *__restrict new_str, internal::ArgList &args)
-      : str(new_str), args_cur(args), args_start(args) {
-    inline_memset(reinterpret_cast<char *>(desc_arr), 0,
-                  DESC_ARR_LEN * sizeof(TypeDesc));
-  }
+      : str(new_str), args_cur(args), args_start(args) {}
 #else
   Parser(const char *__restrict new_str, internal::ArgList &args)
       : str(new_str), args_cur(args) {}