fix: resolve use-afer-free in backup.zig

This worked fine on stage1, and works fine in debug in stage3.
However, stage3 ReleaseSafe would panic due to what I assume must
have been an undefined behaviour optimization.

While I'm happy that I was quickly made aware of the issue thanks to
the safety checks in ReleaseSafe I do wish that this issue showed itself
in Debug, since I *am* using the GPA

src/Gui.zig

@@ -11,7 +11,6 @@ const pitch = @import("core/ppu.zig").framebuf_pitch;
 const scale = @import("core/emu.zig").win_scale;
 
 const emu = @import("core/emu.zig");
-const asString = @import("core/util.zig").asString;
 const log = std.log.scoped(.GUI);
 
 const default_title: []const u8 = "ZBA";

src/core/bus/backup.zig

@@ -3,7 +3,7 @@ const Allocator = std.mem.Allocator;
 const log = std.log.scoped(.Backup);
 
 const escape = @import("../util.zig").escape;
-const asString = @import("../util.zig").asString;
+const asStringSlice = @import("../util.zig").asStringSlice;
 
 const backup_kinds = [5]Needle{
     .{ .str = "EEPROM_V", .kind = .Eeprom },
@@ -72,7 +72,7 @@ pub const Backup = struct {
     }
 
     fn loadSaveFromDisk(self: *Self, path: []const u8) !void {
-        const file_path = try self.getSaveFilePath(path);
+        const file_path = try self.getSaveFilePath(self.alloc, path);
         defer self.alloc.free(file_path);
 
         // FIXME: Don't rely on this lol
@@ -111,22 +111,22 @@ pub const Backup = struct {
         }
     }
 
-    fn getSaveFilePath(self: *const Self, path: []const u8) ![]const u8 {
+    fn getSaveFilePath(self: *const Self, allocator: Allocator, path: []const u8) ![]const u8 {
-        const filename = try self.getSaveFilename();
+        const filename = try self.getSaveFilename(allocator);
-        defer self.alloc.free(filename);
+        defer allocator.free(filename);
 
-        return try std.fs.path.join(self.alloc, &[_][]const u8{ path, filename });
+        return try std.fs.path.join(allocator, &[_][]const u8{ path, filename });
     }
 
-    fn getSaveFilename(self: *const Self) ![]const u8 {
+    fn getSaveFilename(self: *const Self, allocator: Allocator) ![]const u8 {
-        const title = asString(escape(self.title));
+        const title_str = asStringSlice(&escape(self.title));
-        const name = if (title.len != 0) title else "untitled";
+        const name = if (title_str.len != 0) title_str else "untitled";
 
-        return try std.mem.concat(self.alloc, u8, &[_][]const u8{ name, ".sav" });
+        return try std.mem.concat(allocator, u8, &[_][]const u8{ name, ".sav" });
     }
 
     fn writeSaveToDisk(self: Self, path: []const u8) !void {
-        const file_path = try self.getSaveFilePath(path);
+        const file_path = try self.getSaveFilePath(self.alloc, path);
         defer self.alloc.free(file_path);
 
         switch (self.kind) {

src/core/util.zig

@@ -69,7 +69,7 @@ pub fn intToBytes(comptime T: type, value: anytype) [@sizeOf(T)]u8 {
 ///
 /// This function returns a slice of everything just before the first
 /// `\0`
-pub fn asString(title: [12]u8) []const u8 {
+pub fn asStringSlice(title: *const [12]u8) []const u8 {
     var len = title.len;
     for (title) |char, i| {
         if (char == 0) {