Revert "[asan] Use InternalMmapVector for error_message_buffer, reallocate when the size of error_message_buffer is not enough"

This reverts commit 37e6da6.

Author: Enna1

compiler-rt/lib/asan/asan_report.cpp

@@ -32,7 +32,8 @@ namespace __asan {
 
 // -------------------- User-specified callbacks ----------------- {{{1
 static void (*error_report_callback)(const char*);
-static InternalMmapVector<char> *error_message_buffer = nullptr;
+static char *error_message_buffer = nullptr;
+static uptr error_message_buffer_pos = 0;
 static Mutex error_message_buf_mutex;
 static const unsigned kAsanBuggyPcPoolSize = 25;
 static __sanitizer::atomic_uintptr_t AsanBuggyPcPool[kAsanBuggyPcPoolSize];
@@ -41,15 +42,17 @@ void AppendToErrorMessageBuffer(const char *buffer) {
   Lock l(&error_message_buf_mutex);
   if (!error_message_buffer) {
     error_message_buffer =
-        new (GetGlobalLowLevelAllocator()) InternalMmapVector<char>();
-    error_message_buffer->reserve(kErrorMessageBufferSize);
-    error_message_buffer->push_back('\0');
+      (char*)MmapOrDieQuietly(kErrorMessageBufferSize, __func__);
+    error_message_buffer_pos = 0;
   }
-  uptr error_message_buffer_len = error_message_buffer->size() - 1;
-  uptr buffer_len = internal_strlen(buffer);
-  error_message_buffer->resize(error_message_buffer_len + buffer_len + 1);
-  internal_memcpy(error_message_buffer->data() + error_message_buffer_len,
-                  buffer, buffer_len + 1);
+  uptr length = internal_strlen(buffer);
+  RAW_CHECK(kErrorMessageBufferSize >= error_message_buffer_pos);
+  uptr remaining = kErrorMessageBufferSize - error_message_buffer_pos;
+  internal_strncpy(error_message_buffer + error_message_buffer_pos,
+                   buffer, remaining);
+  error_message_buffer[kErrorMessageBufferSize - 1] = '\0';
+  // FIXME: reallocate the buffer instead of truncating the message.
+  error_message_buffer_pos += Min(remaining, length);
 }
 
 // ---------------------- Helper functions ----------------------- {{{1
@@ -155,14 +158,14 @@ class ScopedInErrorReport {
 
     // Copy the message buffer so that we could start logging without holding a
     // lock that gets acquired during printing.
-    InternalScopedString buffer_copy;
+    InternalMmapVector<char> buffer_copy(kErrorMessageBufferSize);
     {
       Lock l(&error_message_buf_mutex);
-      buffer_copy.Append(error_message_buffer->data());
+      internal_memcpy(buffer_copy.data(),
+                      error_message_buffer, kErrorMessageBufferSize);
       // Clear error_message_buffer so that if we find other errors
       // we don't re-log this error.
-      error_message_buffer->clear();
-      error_message_buffer->push_back('\0');
+      error_message_buffer_pos = 0;
     }
 
     LogFullErrorReport(buffer_copy.data());