[libc] [llvm] [libc] add remaining epoll functions, pipe (PR #84587)

[Nick Desaulniers via llvm-commits]

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@@ -0,0 +1,39 @@
+//===---------- Linux implementation of the epoll_create function ---------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/epoll/epoll_create.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(int, epoll_create, (int size)) {
+#ifdef SYS_epoll_create
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_epoll_create, size);
+#elif defined(SYS_epoll_create1)
+  // TODO: Silence warning for size being unused.
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nickdesaulniers wrote:

add `[[gnu::maybe_used]]` on the parameter. `(void) size;` only works for clang but not yet for GCC.

https://github.com/llvm/llvm-project/pull/84587