Convert jpg to webp cause memory leak with imagemagick

Question

My code here:

std::input = "jpeg*****";              //the jpg encode stream
Magick::Blob input_blob((void*) input.c_str(), input.length());

Magick::Image img;
img.read(input_blob);

Magick::Blob blob;
img.write(&blob, "WEBP");
std::string webp_str((char*) blob.data(), blob.length());

When I start the service, the memory begin grow. It show that a memory leak. Anyone has seen this situation? How could I solve this problem?