On Sun, 1 Mar 2026 12:01:08 -0800
Linus Torvalds <[email protected]> wrote:
I also added to compiler.h :
+/*
+ * Sometimes a #define needs to declare a variable that is scoped
+ * to the statement that follows without having mismatched {}.
+ * with (int x = expression) {
+ * statements
+ * }
+ * is the same as:
+ * {
+ * int x = expression;
+ * statements
+ * }
+ * but lets it all be hidden from the call site, eg:
+ * frobnicate(args) {
+ * statements
+ * }
+ * Only a single variable can be defined, and_with() allows extra ones
+ * without adding an additional outer loop.
+ *
+ * The controlled scope can be terminated using break, continue or goto.
+ */
+#define with(declaration) \
+ for (bool _with_done = false; !_with_done; _with_done = true) \
+ and_with (declaration)
+#define and_with(declaration) \
+ for (declaration; !_with_done; _with_done = true)
+
So that you get:
#define __scoped_user_access(mode, uptr, size, elbl)
\
with (auto _tmpptr = __scoped_user_access_begin(mode, uptr, size,
elbl)) \
and_with (CLASS(user_##mode##_access, scope)(_tmpptr))
\
/* Force modified pointer usage within the scope */
\
and_with (const auto uptr = _tmpptr)
The next patch did:
- and_with (const typeof(uptr) uptr = _tmpptr)
+ __diag_push() __diag_ignore_all("-Wshadow", "uptr is readonly
copy") \
+ and_with (const typeof(uptr) uptr = _tmpptr)
\
+ __diag_pop()
I'll update (to use auto as above) and resend.
David
