1 files changed, 55 insertions, 0 deletions
diff --git a/lldb/source/Utility/VASprintf.cpp b/lldb/source/Utility/VASprintf.cpp
new file mode 100644
index 000000000000..2ee0f6676fa7
--- /dev/null
+++ b/lldb/source/Utility/VASprintf.cpp
@@ -0,0 +1,55 @@
+//===-- VASprintf.cpp -------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Utility/VASPrintf.h"
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+
+#include <assert.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+bool lldb_private::VASprintf(llvm::SmallVectorImpl<char> &buf, const char *fmt,
+                             va_list args) {
+  llvm::SmallString<16> error("<Encoding error>");
+  bool result = true;
+
+  // Copy in case our first call to vsnprintf doesn't fit into our buffer
+  va_list copy_args;
+  va_copy(copy_args, args);
+
+  buf.resize(buf.capacity());
+  // Write up to `capacity` bytes, ignoring the current size.
+  int length = ::vsnprintf(buf.data(), buf.size(), fmt, args);
+  if (length < 0) {
+    buf = error;
+    result = false;
+    goto finish;
+  }
+
+  if (size_t(length) >= buf.size()) {
+    // The error formatted string didn't fit into our buffer, resize it to the
+    // exact needed size, and retry
+    buf.resize(length + 1);
+    length = ::vsnprintf(buf.data(), buf.size(), fmt, copy_args);
+    if (length < 0) {
+      buf = error;
+      result = false;
+      goto finish;
+    }
+    assert(size_t(length) < buf.size());
+  }
+  buf.resize(length);
+
+finish:
+  va_end(args);
+  va_end(copy_args);
+  return result;
+}