[libc-commits] [PATCH] D154519: [libc] Support fopen / fclose on the GPU

[Joseph Huber via Phabricator via libc-commits]

jhuber6 added a comment.

In D154519#4475537 <https://reviews.llvm.org/D154519#4475537>, @JonChesterfield wrote:

> There's a design question in here I think. Specifically whether FILE* is some handle to a host only thing or something that lives on the GPU. I can see arguments both ways, this LGTM too.

So that's something I was wondering about, because as it stands the following will not work if we're doing an offloading language

  int main() {
    FILE *fp = fopen("foo.txt", "w");
  #pragma omp target
    { fputs("foo", fp); }
  }

This is because these both represent fundamentally different structs. We could potentially make the interface just a `uintptr_t` to a host `FILE *`, but this would necessitate bypassing completely the file abstractions in `libc` and implementing each entrypoint separate on the GPU, versus what we do now where we more or less treat RPC as the syscall. We could potentially detect if a `FILE *` came from us or the host via pointer tagging in the LSB, that would allow us to wrap it in a new file if needed, but going from the GPU to the CPU then still wouldn't work. Alternatively we can just be like "Don't mix the two they're not the same `libc`" and call it a day.


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https://reviews.llvm.org/D154519