From 2fb6915fa22dc5524d704afba58a13305dd9f533 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 18 Jul 2025 11:35:00 -0700 Subject: compiler_types.h: add "auto" as a macro for "__auto_type" "auto" was defined as a keyword back in the K&R days, but as a storage type specifier. No one ever used it, since it was and is the default storage type for local variables. C++11 recycled the keyword to allow a type to be declared based on the type of an initializer. This was finally adopted into standard C in C23. gcc and clang provide the "__auto_type" alias keyword as an extension for pre-C23, however, there is no reason to pollute the bulk of the source base with this temporary keyword; instead define "auto" as a macro unless the compiler is running in C23+ mode. This macro is added in because that header is included in some of the tools headers, wheres is not as it has a bunch of very kernel-specific things in it. [ Cc: stable to reduce potential backporting burden. ] Signed-off-by: H. Peter Anvin (Intel) Acked-by: Miguel Ojeda Cc: --- include/linux/compiler_types.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/linux') diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 3eac51d68426..41172a28ce76 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -13,6 +13,19 @@ #ifndef __ASSEMBLY__ +/* + * C23 introduces "auto" as a standard way to define type-inferred + * variables, but "auto" has been a (useless) keyword even since K&R C, + * so it has always been "namespace reserved." + * + * Until at some future time we require C23 support, we need the gcc + * extension __auto_type, but there is no reason to put that elsewhere + * in the source code. + */ +#if __STDC_VERSION__ < 202311L +# define auto __auto_type +#endif + /* * Skipped when running bindgen due to a libclang issue; * see https://github.com/rust-lang/rust-bindgen/issues/2244. -- cgit v1.2.3 From b3b8767c290102a8d95b9d12585cc1e03381ce3f Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Sat, 19 Jul 2025 23:36:58 -0700 Subject: include/linux: change "__auto_type" to "auto" Replace instances of "__auto_type" with "auto" in include/linux. Signed-off-by: H. Peter Anvin (Intel) --- include/linux/cleanup.h | 6 +++--- include/linux/compiler.h | 2 +- include/linux/minmax.h | 6 +++--- 3 files changed, 7 insertions(+), 7 deletions(-) (limited to 'include/linux') diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h index 0b55a8f6c59e..8d41b917c77d 100644 --- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -212,10 +212,10 @@ #define __free(_name) __cleanup(__free_##_name) -#define __get_and_null(p, nullvalue) \ +#define __get_and_null(p, nullvalue) \ ({ \ - __auto_type __ptr = &(p); \ - __auto_type __val = *__ptr; \ + auto __ptr = &(p); \ + auto __val = *__ptr; \ *__ptr = nullvalue; \ __val; \ }) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ff71bebe56f5..04487c9bd751 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -190,7 +190,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #define data_race(expr) \ ({ \ __kcsan_disable_current(); \ - __auto_type __v = (expr); \ + auto __v = (expr); \ __kcsan_enable_current(); \ __v; \ }) diff --git a/include/linux/minmax.h b/include/linux/minmax.h index eaaf5c008e4d..a0158db54a04 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -89,7 +89,7 @@ __cmp_once_unique(op, type, x, y, __UNIQUE_ID(x_), __UNIQUE_ID(y_)) #define __careful_cmp_once(op, x, y, ux, uy) ({ \ - __auto_type ux = (x); __auto_type uy = (y); \ + auto ux = (x); auto uy = (y); \ BUILD_BUG_ON_MSG(!__types_ok(ux, uy), \ #op"("#x", "#y") signedness error"); \ __cmp(op, ux, uy); }) @@ -129,7 +129,7 @@ __careful_cmp(max, (x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull) #define __careful_op3(op, x, y, z, ux, uy, uz) ({ \ - __auto_type ux = (x); __auto_type uy = (y);__auto_type uz = (z);\ + auto ux = (x); auto uy = (y); auto uz = (z); \ BUILD_BUG_ON_MSG(!__types_ok3(ux, uy, uz), \ #op"3("#x", "#y", "#z") signedness error"); \ __cmp(op, ux, __cmp(op, uy, uz)); }) @@ -203,7 +203,7 @@ * This macro checks @val/@lo/@hi to make sure they have compatible * signedness. */ -#define clamp(val, lo, hi) __careful_clamp(__auto_type, val, lo, hi) +#define clamp(val, lo, hi) __careful_clamp(auto, val, lo, hi) /** * clamp_t - return a value clamped to a given range using a given type -- cgit v1.2.3