#include "llvm/ADT/SmallString.h" #includeIn this example, two SmallStrings are created, "Hello " and "world". The append function is called on the first SmallString, S1, to concatenate it with S2. The result, "Hello world", is printed to the console using the str() function. The code makes use of the LLVM/ADT/SmallString.h header file which is part of the LLVM's StringRef library. The library provides a set of string manipulation functions that are optimized for performance and memory usage. It is part of the LLVM project which is distributed under the University of Illinois open source license.int main() { llvm::SmallString<16> S1("Hello "); llvm::SmallString<16> S2("world"); S1.append(S2); std::cout << S1.str() << std::endl; return 0; }