From 91040b567863e7c068b21d7c6bbf76a1d28a2b2d Mon Sep 17 00:00:00 2001
From: Sardorbek Imomaliev <3041675+imomaliev@users.noreply.github.com>
Date: Mon, 25 Aug 2025 20:25:53 +0100
Subject: [PATCH] add macOS handling for totalSystemMemory (#24903)

* add macos handling for totalSystemMemory

* fix return type cast for .freebsd in totalSystemMemory

* add handling for the whole Darwin family in totalSystemMemory
---
 lib/std/process.zig | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/std/process.zig b/lib/std/process.zig
index 360c3f6af0..1f86ca658a 100644
--- a/lib/std/process.zig
+++ b/lib/std/process.zig
@@ -1762,7 +1762,20 @@ pub fn totalSystemMemory() TotalSystemMemoryError!u64 {
                 error.UnknownName => unreachable,
                 else => return error.UnknownTotalSystemMemory,
             };
-            return @as(usize, @intCast(physmem));
+            return @as(u64, @intCast(physmem));
+        },
+        // whole Darwin family
+        .driverkit, .ios, .macos, .tvos, .visionos, .watchos => {
+            // "hw.memsize" returns uint64_t
+            var physmem: u64 = undefined;
+            var len: usize = @sizeOf(u64);
+            posix.sysctlbynameZ("hw.memsize", &physmem, &len, null, 0) catch |err| switch (err) {
+                error.PermissionDenied => unreachable, // only when setting values,
+                error.SystemResources => unreachable, // memory already on the stack
+                error.UnknownName => unreachable, // constant, known good value
+                else => return error.UnknownTotalSystemMemory,
+            };
+            return physmem;
         },
         .openbsd => {
             const mib: [2]c_int = [_]c_int{