From 3375a97c399cd9263281a27e895ec6ba984a1a53 Mon Sep 17 00:00:00 2001
From: Reuben Dunnington <reuben.dunnington@gmail.com>
Date: Wed, 16 Aug 2023 10:57:27 -0700
Subject: [PATCH] darwin: fix madvise

---
 stable_array.zig | 33 +++++++++++----------------------
 1 file changed, 11 insertions(+), 22 deletions(-)

diff --git a/stable_array.zig b/stable_array.zig
index ac64e0e..acf8e95 100644
--- a/stable_array.zig
+++ b/stable_array.zig
@@ -4,6 +4,10 @@ const os = std.os;
 const mem = std.mem;
 const assert = std.debug.assert;
 
+const darwin = struct {
+    extern "c" fn madvise(ptr: [*]align(mem.page_size) u8, length: usize, advice: c_int) c_int;
+};
+
 pub fn StableArray(comptime T: type) type {
     return StableArrayAligned(T, @alignOf(T));
 }
@@ -204,7 +208,12 @@ pub fn StableArrayAligned(comptime T: type, comptime alignment: u29) type {
                     var addr: [*]align(mem.page_size) u8 = @alignCast(mem.page_size, @intToPtr([*]u8, offset_addr));
                     if (comptime builtin.target.isDarwin()) {
                         const MADV_DONTNEED = 4;
-                        darwin_madvise(addr, bytes_to_free, MADV_DONTNEED) catch unreachable;
+                        const err: c_int = darwin.madvise(addr, bytes_to_free, MADV_DONTNEED);
+                        switch (@intToEnum(os.darwin.E, err)) {
+                            os.E.INVAL => unreachable,
+                            os.E.NOMEM => unreachable,
+                            else => {},
+                        }
                     } else {
                         os.madvise(addr, bytes_to_free, std.c.MADV.DONTNEED) catch unreachable;
                     }
@@ -315,27 +324,6 @@ pub fn StableArrayAligned(comptime T: type, comptime alignment: u29) type {
     };
 }
 
-fn darwin_syscall3(number: usize, arg1: usize, arg2: usize, arg3: usize) usize {
-    return asm volatile ("syscall"
-        : [ret] "={rax}" (-> usize),
-        : [number] "{rax}" (number),
-          [arg1] "{rdi}" (arg1),
-          [arg2] "{rsi}" (arg2),
-          [arg3] "{rdx}" (arg3),
-        : "rcx", "r11", "memory"
-    );
-}
-
-fn darwin_madvise(ptr: [*]align(mem.page_size) u8, length: usize, advice: u32) os.MadviseError!void {
-    if (darwin_syscall3(75, @ptrToInt(ptr), length, advice) == -1) {
-        return switch (os.errno()) {
-            os.c.INVAL => os.MadviseError.InvalidSyscall,
-            os.c.ENOMEM => os.MadviseError.OutOfMemory,
-            else => os.MadviseError.Unexpected,
-        };
-    }
-}
-
 const TEST_VIRTUAL_ALLOC_SIZE = 1024 * 1024 * 2; // 2 MB
 
 test "init" {
@@ -374,6 +362,7 @@ test "shrinkAndFree" {
     var a = StableArray(u8).init(TEST_VIRTUAL_ALLOC_SIZE);
     try a.appendSlice(&[_]u8{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 });
     a.shrinkAndFree(5);
+
     assert(a.calcTotalUsedBytes() == mem.page_size);
     assert(a.items.len == 5);
     for (a.items) |v, i| {