From ab5a72f6ca9446820f3f516873e1b5d1aeefb5a8 Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Sun, 14 May 2023 12:48:11 +0300
Subject: [PATCH] Sema: ensure dest ptr of memcpy has length

Closes #15513
---
 src/Sema.zig             | 12 ++++++++++++
 test/behavior/memcpy.zig | 21 +++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/Sema.zig b/src/Sema.zig
index 1b55f765f9..f0ebd65a31 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -22130,6 +22130,14 @@ fn zirMemcpy(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!void
             const ok = try block.addBinOp(.cmp_eq, dest_len, src_len);
             try sema.addSafetyCheck(block, ok, .memcpy_len_mismatch);
         }
+    } else if (dest_len != .none) {
+        if (try sema.resolveDefinedValue(block, dest_src, dest_len)) |dest_len_val| {
+            len_val = dest_len_val;
+        }
+    } else if (src_len != .none) {
+        if (try sema.resolveDefinedValue(block, src_src, src_len)) |src_len_val| {
+            len_val = src_len_val;
+        }
     }
 
     const runtime_src = if (try sema.resolveDefinedValue(block, dest_src, dest_ptr)) |dest_ptr_val| rs: {
@@ -22213,6 +22221,10 @@ fn zirMemcpy(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!void
         if (new_src_ptr_ty.isSlice()) {
             new_src_ptr = try sema.analyzeSlicePtr(block, src_src, new_src_ptr, new_src_ptr_ty);
         }
+    } else if (dest_len == .none and len_val == null) {
+        // Change the dest to a slice, since its type must have the length.
+        const dest_ptr_ptr = try sema.analyzeRef(block, dest_src, new_dest_ptr);
+        new_dest_ptr = try sema.analyzeSlice(block, dest_src, dest_ptr_ptr, .zero, src_len, .none, .unneeded, dest_src, dest_src, dest_src, false);
     }
 
     try sema.requireRuntimeBlock(block, src, runtime_src);
diff --git a/test/behavior/memcpy.zig b/test/behavior/memcpy.zig
index 66657b26c9..a2aad42402 100644
--- a/test/behavior/memcpy.zig
+++ b/test/behavior/memcpy.zig
@@ -44,3 +44,24 @@ fn testMemcpyBothSinglePtrArrayOneIsNullTerminated() !void {
     try expect(buf[98] == 'l');
     try expect(buf[99] == 'o');
 }
+
+test "@memcpy dest many pointer" {
+    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_spirv64) return error.SkipZigTest;
+
+    try testMemcpyDestManyPtr();
+    try comptime testMemcpyDestManyPtr();
+}
+
+fn testMemcpyDestManyPtr() !void {
+    var str = "hello".*;
+    var buf: [5]u8 = undefined;
+    @memcpy(@ptrCast([*]u8, &buf), @ptrCast([*]const u8, &str)[0..5]);
+    try expect(buf[0] == 'h');
+    try expect(buf[1] == 'e');
+    try expect(buf[2] == 'l');
+    try expect(buf[3] == 'l');
+    try expect(buf[4] == 'o');
+}