Summary: These were originally intended to represent the functions that are present on the GPU as to be provided by the LLVM libc implementation. The original plan was that LLVM libc would report which functions were supported and then the offload interface would mark those as supported. The problem is that these wrapper headers are very difficult to make work given the various libc extensions everyone does so they were extremely fragile. OpenMP already declares all functions used inside of a target region as implicitly host / device, while these headers weren't even used for CUDA / HIP yet anyway. The only things we need to define right now are the stdio FILE types. If we want to make this work for CUDA we'd need to define these manually, but we're a ways off and that's way easier because they do proper overloading.
The LLVM Compiler Infrastructure
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