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- [libc][GPU] ftell: use the LIBC_FTELL opcode instead of LIBC_FSEEK
- The GPU ftell() opened the RPC port with LIBC_FSEEK and only filled data[0].
- The host server then called fseek(stream, data[1], data[2]) with whatever was
- left in the buffer from a previous message. glibc just returns EINVAL, so the
- bug is silent on Linux; the MSVC CRT treats an invalid 'origin' as an invalid
- parameter and terminates the process (0xC0000409, FAST_FAIL_INVALID_ARG).
- Still present in llvm-project main as of 2026-10.
- --- a/libc/src/stdio/gpu/ftell.cpp
- +++ b/libc/src/stdio/gpu/ftell.cpp
- @@ -16,7 +16,7 @@
- LLVM_LIBC_FUNCTION(long, ftell, (::FILE * stream)) {
- long ret;
- - rpc::Client::Port port = rpc::client.open<LIBC_FSEEK>();
- + rpc::Client::Port port = rpc::client.open<LIBC_FTELL>();
- port.send_and_recv(
- [=](rpc::Buffer *buffer, uint32_t) {
- buffer->data[0] = file::from_stream(stream);
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