I am working on a project for which I need to "combine" code distributed over multiple C++ files into one file. Due to the nature of the project, I only need one entry function (the function that will be defined as the top function in the Xilinx High-Level-Synthesis software -> see context below). The signature of this function needs to be preserved in the transformation. Whether other functions from other files simply get copied into the file and get called as a subroutine or are inlined does not matter. I think due to variable and function scopes simply concatenating the files will not work.

Since I did not write the C++ code myself and it is quite comprehensive, I am looking for a way to do the transformation automatically. The possibilities I am aware of to do this are the following:

1. Compile the code to LLVM IR with inlining flags and use a C++/C backend to turn the LLVM code into the source language again. This will result in bad source code and require either an old release of Clang and LLVM or another backend like JuliaComputing. 1
2. The other option would be developing a tool that relies on using the AST and a library like LibTooling to restructure the code. This option would probably result in better code and put everything into one file without the unnecessary inlining. 2 However, this options seems too complicated to put the all the code into one file.

Hence my question: Are you aware of a better or simply alternative approach to solve this problem?

Context: The project aims to run some of the code on a Xilinx FPGA and the Vitis High-Level-Synthesis tool requires all code that is to be made into a single IP block to be contained in a single file. That is why I need to realise this transformation.