Fix a crash in FormatStringIntoVector

src/common/angleutils.cpp

@@ -49,26 +49,26 @@ std::string ArrayIndexString(const std::vector<unsigned int> &indices)
 
 size_t FormatStringIntoVector(const char *fmt, va_list vararg, std::vector<char> &outBuffer)
 {
-    // The state of the va_list passed to vsnprintf is undefined after the call, do a copy in case
-    // we need to grow the buffer.
+    // The state of the va_list passed to vsnprintf is undefined after the call,
+    // do a copy since we don't want to interfere with vararg usage inside the caller.
     va_list varargCopy;
     va_copy(varargCopy, vararg);
 
     // Attempt to just print to the current buffer
     int len = vsnprintf(&(outBuffer.front()), outBuffer.size(), fmt, varargCopy);
     va_end(varargCopy);
+    ASSERT(len >= 0);
 
-    if (len < 0 || static_cast<size_t>(len) >= outBuffer.size())
+    if (static_cast<size_t>(len) >= outBuffer.size())
     {
-        // Buffer was not large enough, calculate the required size and resize the buffer
-        len = vsnprintf(nullptr, 0, fmt, vararg);
+        // Buffer was not large enough, resize it
         outBuffer.resize(len + 1);
 
         // Print again
         va_copy(varargCopy, vararg);
         len = vsnprintf(&(outBuffer.front()), outBuffer.size(), fmt, varargCopy);
         va_end(varargCopy);
+        ASSERT(len >= 0);
     }
-    ASSERT(len >= 0);
     return static_cast<size_t>(len);
 }