[compiler-rt] [libc] [libc][sched] Implement proxy headers for `cpu_set_t`, `struct sched_param` and `sched_macros`. (PR #126303)

[Krishna Pandey via llvm-commits]

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@@ -0,0 +1,27 @@
+//===-- Definition of macros from sched.h ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_HDR_SCHED_MACROS_H
+#define LLVM_LIBC_HDR_SCHED_MACROS_H
+
+#ifdef LIBC_FULL_BUILD
+
+#ifndef _SCHED_H
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krishna2803 wrote:

The source `compiler-rt/lib/scudo/standalone/linux.cpp` that is causing the errors uses `sched.h`:

https://github.com/llvm/llvm-project/blob/3f67c42904757958fe9b30db1e37429ef1c0dfde/compiler-rt/lib/scudo/standalone/linux.cpp#L23

in the function `getNumberOfCPUs`:

https://github.com/llvm/llvm-project/blob/3f67c42904757958fe9b30db1e37429ef1c0dfde/compiler-rt/lib/scudo/standalone/linux.cpp#L164-L171

which is declared in `common.h`

https://github.com/llvm/llvm-project/blob/3f67c42904757958fe9b30db1e37429ef1c0dfde/compiler-rt/lib/scudo/standalone/common.h#L170-L171

we already have definitions for `cpu_set_t` and `sched_getaffinity` but not for `CPU_COUNT`. I planned on first implementing the proxy headers for `sched.h` related definitions and then work on #124642 for the implementation of those macros but it seems there's a cyclic dependency within these issues. Since `sched.h` is not too big of a header, I think we should go with the 1st approach:

> 1. Fulfilling our sched.h related headers to be complete enough so that usr/include/sched.h is not needed anymore in full build mode

@lntue How should I proceed? Should I complete #124642 prior to this, or implement CPU_COUNT within this PR only, which should complete the requirements for Scudo for now?

https://github.com/llvm/llvm-project/pull/126303