From de709146e46d7c793d644c094696f8df2833076d Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sun, 23 Apr 2023 15:26:57 -0700
Subject: [PATCH] add behavior test for `@memset` on slices

and avoid new language feature in std.ArrayList for now, until x86_64
self-hosted backend can implement it.
---
 lib/std/array_list.zig  | 16 +++++++++++--
 test/behavior/basic.zig | 50 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/lib/std/array_list.zig b/lib/std/array_list.zig
index 1791482bc4db..54bed28285bb 100644
--- a/lib/std/array_list.zig
+++ b/lib/std/array_list.zig
@@ -121,7 +121,13 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
 
             const new_memory = try allocator.alignedAlloc(T, alignment, self.items.len);
             mem.copy(T, new_memory, self.items);
-            @memset(self.items, undefined);
+
+            // TODO: write like this instead:
+            //@memset(self.items, undefined);
+            // first we need to implement memset with element ABI size > 1 in
+            // the x86_64 selfhosted backend.
+            @memset(@ptrCast([*]u8, self.items.ptr)[0..self.items.len * @sizeOf(T)], undefined);
+
             self.clearAndFree();
             return new_memory;
         }
@@ -597,7 +603,13 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
 
             const new_memory = try allocator.alignedAlloc(T, alignment, self.items.len);
             mem.copy(T, new_memory, self.items);
-            @memset(self.items, undefined);
+
+            // TODO: write like this instead:
+            //@memset(self.items, undefined);
+            // first we need to implement memset with element ABI size > 1 in
+            // the x86_64 selfhosted backend.
+            @memset(@ptrCast([*]u8, self.items.ptr)[0..self.items.len * @sizeOf(T)], undefined);
+
             self.clearAndFree(allocator);
             return new_memory;
         }
diff --git a/test/behavior/basic.zig b/test/behavior/basic.zig
index a1ea2c340f4f..a59397d0b5eb 100644
--- a/test/behavior/basic.zig
+++ b/test/behavior/basic.zig
@@ -357,6 +357,14 @@ test "@memset on array pointers" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_wasm) {
+        // TODO: implement memset when element ABI size > 1
+        return error.SkipZigTest;
+    }
+    if (builtin.zig_backend == .stage2_x86_64) {
+        // TODO: implement memset when element ABI size > 1
+        return error.SkipZigTest;
+    }
 
     try testMemsetArray();
     try comptime testMemsetArray();
@@ -381,6 +389,48 @@ fn testMemsetArray() !void {
     }
 }
 
+test "@memset on slices" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_wasm) {
+        // TODO: implement memset when element ABI size > 1
+        // TODO: implement memset on slices
+        return error.SkipZigTest;
+    }
+    if (builtin.zig_backend == .stage2_x86_64) {
+        // TODO: implement memset when element ABI size > 1
+        // TODO: implement memset on slices
+        return error.SkipZigTest;
+    }
+
+    try testMemsetSlice();
+    try comptime testMemsetSlice();
+}
+
+fn testMemsetSlice() !void {
+    {
+        // memset slice to non-undefined, ABI size == 1
+        var array: [20]u8 = undefined;
+        var len = array.len;
+        var slice = array[0..len];
+        @memset(slice, 'A');
+        try expect(slice[0] == 'A');
+        try expect(slice[11] == 'A');
+        try expect(slice[19] == 'A');
+    }
+    {
+        // memset slice to non-undefined, ABI size > 1
+        var array: [20]u32 = undefined;
+        var len = array.len;
+        var slice = array[0..len];
+        @memset(slice, 1234);
+        try expect(slice[0] == 1234);
+        try expect(slice[11] == 1234);
+        try expect(slice[19] == 1234);
+    }
+}
+
 test "memcpy and memset intrinsics" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;