fix std.mem.addNullByte and implement sentinel slicing

see #3770

1 files changed, 9 insertions, 16 deletions

diff --git a/lib/std/os.zig b/lib/std/os.zig
index 6d49bcd38e..3cc43357bd 100644
--- a/lib/std/os.zig
+++ b/lib/std/os.zig
@@ -805,9 +805,9 @@ pub fn execvpeC(file: [*:0]const u8, child_argv: [*:null]const ?[*:0]const u8, e
         mem.copy(u8, &path_buf, search_path);
         path_buf[search_path.len] = '/';
         mem.copy(u8, path_buf[search_path.len + 1 ..], file_slice);
-        path_buf[search_path.len + file_slice.len + 1] = 0;
-        // TODO avoid @ptrCast here using slice syntax with https://github.com/ziglang/zig/issues/3770
-        err = execveC(@ptrCast([*:0]u8, &path_buf), child_argv, envp);
+        const path_len = search_path.len + file_slice.len + 1;
+        path_buf[path_len] = 0;
+        err = execveC(path_buf[0..path_len :0].ptr, child_argv, envp);
         switch (err) {
             error.AccessDenied => seen_eacces = true,
             error.FileNotFound, error.NotDir => {},
@@ -841,18 +841,14 @@ pub fn execvpe(
         const arg_buf = try allocator.alloc(u8, arg.len + 1);
         @memcpy(arg_buf.ptr, arg.ptr, arg.len);
         arg_buf[arg.len] = 0;
-
-        // TODO avoid @ptrCast using slice syntax with https://github.com/ziglang/zig/issues/3770
-        argv_buf[i] = @ptrCast([*:0]u8, arg_buf.ptr);
+        argv_buf[i] = arg_buf[0..arg.len :0].ptr;
     }
     argv_buf[argv_slice.len] = null;
+    const argv_ptr = argv_buf[0..argv_slice.len :null].ptr;
 
     const envp_buf = try createNullDelimitedEnvMap(allocator, env_map);
     defer freeNullDelimitedEnvMap(allocator, envp_buf);
 
-    // TODO avoid @ptrCast here using slice syntax with https://github.com/ziglang/zig/issues/3770
-    const argv_ptr = @ptrCast([*:null]?[*:0]u8, argv_buf.ptr);
-
     return execvpeC(argv_buf.ptr[0].?, argv_ptr, envp_buf.ptr);
 }
 
@@ -869,16 +865,13 @@ pub fn createNullDelimitedEnvMap(allocator: *mem.Allocator, env_map: *const std.
             @memcpy(env_buf.ptr, pair.key.ptr, pair.key.len);
             env_buf[pair.key.len] = '=';
             @memcpy(env_buf.ptr + pair.key.len + 1, pair.value.ptr, pair.value.len);
-            env_buf[env_buf.len - 1] = 0;
-
-            // TODO avoid @ptrCast here using slice syntax with https://github.com/ziglang/zig/issues/3770
-            envp_buf[i] = @ptrCast([*:0]u8, env_buf.ptr);
+            const len = env_buf.len - 1;
+            env_buf[len] = 0;
+            envp_buf[i] = env_buf[0..len :0].ptr;
         }
         assert(i == envp_count);
     }
-    // TODO avoid @ptrCast here using slice syntax with https://github.com/ziglang/zig/issues/3770
-    assert(envp_buf[envp_count] == null);
-    return @ptrCast([*:null]?[*:0]u8, envp_buf.ptr)[0..envp_count];
+    return envp_buf[0..envp_count :null];
 }
 
 pub fn freeNullDelimitedEnvMap(allocator: *mem.Allocator, envp_buf: []?[*:0]u8) void {