[libc-commits] [libc] [libc] Fix Darwin aarch64 fenv and sigsetjmp build support (PR #192079)

[Michael Jones via libc-commits]

================
@@ -0,0 +1,47 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation header for sigprocmask.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_OSUTIL_DARWIN_SYSCALL_WRAPPERS_SIGPROCMASK_H
+#define LLVM_LIBC_SRC___SUPPORT_OSUTIL_DARWIN_SYSCALL_WRAPPERS_SIGPROCMASK_H
+
+#include "hdr/stdint_proxy.h"
+#include "hdr/types/sigset_t.h"
+#include "src/__support/OSUtil/darwin/syscall.h" // syscall_impl
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+namespace darwin_syscalls {
+
+LIBC_INLINE ErrorOr<int> sigprocmask(int how, const sigset_t *set,
+                                     sigset_t *oldset) {
+  int ret = syscall_impl<int>(SYS_sigprocmask, how, set, oldset);
+  if (ret != 0)
+    return Error(ret);
+
+  if (oldset) {
+    uint32_t kernel_oldset;
+    __builtin_memcpy(&kernel_oldset, oldset, sizeof(kernel_oldset));
+    oldset->__signals[0] =
+        static_cast<unsigned long>(kernel_oldset & 0x7FFFFFFFU);
+  }
+  return ret;
----------------
michaelrj-google wrote:

it seems like MacOS expects `sigset_t` to be 32 bits and we'll probably want to update the definition in a followup PR. Given that it'd probably be better to reorder this so we don't have to copy the data around as much. I'd also recommend adding a TODO about updating `sigset_t`.
```suggestion
LIBC_INLINE ErrorOr<int> sigprocmask(int how, const sigset_t *set,
                                     sigset_t *oldset) {
  uint32_t kernel_set = set ? static_cast<uint32_t>(set->__signals[0]) : 0;
  uint32_t kernel_oldset = 0;
  int ret = syscall_impl<int>(SYS_sigprocmask, how,
                              set ? &kernel_set : nullptr,
                              oldset ? &kernel_oldset : nullptr);
  if (ret != 0)
    return Error(ret);

  if (oldset)
    oldset->__signals[0] =
        static_cast<unsigned long>(kernel_oldset & 0x7FFFFFFFU);
  return ret;
```

https://github.com/llvm/llvm-project/pull/192079