[libc-commits] [libc] add mremap (PR #112804)

[Michael Jones via libc-commits]

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@@ -0,0 +1,48 @@
+//===---------- Linux implementation of the POSIX mremap 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/mman/mremap.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include "src/__support/macros/config.h"
+#include "src/errno/libc_errno.h"
+#include <linux/param.h> // For EXEC_PAGESIZE.
+#include <stdarg.h>
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(void *, mremap,
+                   (void *old_address, size_t old_size, size_t new_size,
+                    int flags, ... /* void *new_address */)) {
+
+  long ret = 0;
+  void *new_address = nullptr;
+  if (flags & MREMAP_FIXED) {
+    va_list varargs;
+    va_start(varargs, flags);
+    new_address = va_arg(varargs, void *);
+    va_end(varargs);
+    ret = LIBC_NAMESPACE::syscall_impl<long>(SYS_mremap, old_address, old_size,
----------------
michaelrj-google wrote:

you can move this call outside of the `if`. The extra argument will be ignored by the syscall if it's not used.

https://github.com/llvm/llvm-project/pull/112804