fix: EnvStr.initSlice handles zero length strings more reliably. (#9698)

* fix intcast on ptr value of zero-length strings

* Make this better

---------

Co-authored-by: Jarred Sumner <[email protected]>
Co-authored-by: Jarred Sumner <[email protected]>

src/shell/interpreter.zig

@@ -358,38 +358,55 @@ pub const IO = struct {
 /// So environment strings can be ref counted or borrowed slices
 pub const EnvStr = packed struct {
  ptr: u48,
- tag: Tag,
+ tag: Tag = .empty,
  len: usize = 0,
 
  const print = bun.Output.scoped(.EnvStr, true);
 
  const Tag = enum(u16) {
+ /// no value
+ empty,
+
  /// Dealloced by reference counting
  refcounted,
+
  /// Memory is managed elsewhere so don't dealloc it
  slice,
  };
 
  inline fn initSlice(str: []const u8) EnvStr {
+ if (str.len == 0)
+ // Zero length strings may have invalid pointers, leading to a bad integer cast.
+ return .{ .tag = .empty, .ptr = 0, .len = 0 };
+
  return .{
- .ptr = @intCast(@intFromPtr(str.ptr)),
+ .ptr = toPtr(str.ptr),
  .tag = .slice,
  .len = str.len,
  };
  }
 
+ fn toPtr(ptr_val: *const anyopaque) u48 {
+ const num: [8]u8 = @bitCast(@intFromPtr(ptr_val));
+ return @bitCast(num[0..6].*);
+ }
+
  fn initRefCounted(str: []const u8) EnvStr {
+ if (str.len == 0)
+ return .{ .tag = .empty, .ptr = 0, .len = 0 };
+
  return .{
- .ptr = @intCast(@intFromPtr(RefCountedStr.init(str))),
+ .ptr = toPtr(RefCountedStr.init(str)),
  .tag = .refcounted,
  };
  }
 
  pub fn slice(this: EnvStr) []const u8 {
- if (this.asRefCounted()) |refc| {
- return refc.byteSlice();
- }
- return this.castSlice();
+ return switch (this.tag) {
+ .empty => "",
+ .slice => this.castSlice(),
+ .refcounted => this.castRefCounted().byteSlice(),
+ };
  }
 
  fn ref(this: EnvStr) void {