From eb350d1d01d9b9df0ce174e2e1681699b071bab3 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 25 Jun 2024 13:12:20 +0200 Subject: [PATCH] include: move typeof_strip_qual to compiler.h, use it in QAPI_LIST_LENGTH() The typeof_strip_qual() is most useful for the atomic fetch-and-modify operations in atomic.h, but it can be used elsewhere as well. For example, QAPI_LIST_LENGTH() assumes that the argument is not const, which is not a requirement. Move the macro to compiler.h and, while at it, move it under #ifndef __cplusplus to emphasize that it uses C-only constructs. A C++ version of typeof_strip_qual() using type traits is possible[1], but beyond the scope of this patch because the little C++ code that is in QEMU does not use QAPI. The patch was tested by changing the declaration of strv_from_str_list() in qapi/qapi-type-helpers.c to: char **strv_from_str_list(const strList *const list) This is valid C code, and it fails to compile without this change. [1] https://lore.kernel.org/qemu-devel/20240624205647.112034-1-flwu@google.com/ Reviewed-by: Richard Henderson Reviewed-by: Manos Pitsidianakis Tested-by: Manos Pitsidianakis Signed-off-by: Paolo Bonzini --- include/qapi/util.h | 2 +- include/qemu/atomic.h | 42 ------------------------------------- include/qemu/compiler.h | 46 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 47 insertions(+), 43 deletions(-) diff --git a/include/qapi/util.h b/include/qapi/util.h index 20dfea8a54..b8254247b8 100644 --- a/include/qapi/util.h +++ b/include/qapi/util.h @@ -62,7 +62,7 @@ int parse_qapi_name(const char *name, bool complete); #define QAPI_LIST_LENGTH(list) \ ({ \ size_t _len = 0; \ - typeof(list) _tail; \ + typeof_strip_qual(list) _tail; \ for (_tail = list; _tail != NULL; _tail = _tail->next) { \ _len++; \ } \ diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 99110abefb..dc4118ddd9 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -20,48 +20,6 @@ /* Compiler barrier */ #define barrier() ({ asm volatile("" ::: "memory"); (void)0; }) -/* The variable that receives the old value of an atomically-accessed - * variable must be non-qualified, because atomic builtins return values - * through a pointer-type argument as in __atomic_load(&var, &old, MODEL). - * - * This macro has to handle types smaller than int manually, because of - * implicit promotion. int and larger types, as well as pointers, can be - * converted to a non-qualified type just by applying a binary operator. - */ -#define typeof_strip_qual(expr) \ - typeof( \ - __builtin_choose_expr( \ - __builtin_types_compatible_p(typeof(expr), bool) || \ - __builtin_types_compatible_p(typeof(expr), const bool) || \ - __builtin_types_compatible_p(typeof(expr), volatile bool) || \ - __builtin_types_compatible_p(typeof(expr), const volatile bool), \ - (bool)1, \ - __builtin_choose_expr( \ - __builtin_types_compatible_p(typeof(expr), signed char) || \ - __builtin_types_compatible_p(typeof(expr), const signed char) || \ - __builtin_types_compatible_p(typeof(expr), volatile signed char) || \ - __builtin_types_compatible_p(typeof(expr), const volatile signed char), \ - (signed char)1, \ - __builtin_choose_expr( \ - __builtin_types_compatible_p(typeof(expr), unsigned char) || \ - __builtin_types_compatible_p(typeof(expr), const unsigned char) || \ - __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \ - __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \ - (unsigned char)1, \ - __builtin_choose_expr( \ - __builtin_types_compatible_p(typeof(expr), signed short) || \ - __builtin_types_compatible_p(typeof(expr), const signed short) || \ - __builtin_types_compatible_p(typeof(expr), volatile signed short) || \ - __builtin_types_compatible_p(typeof(expr), const volatile signed short), \ - (signed short)1, \ - __builtin_choose_expr( \ - __builtin_types_compatible_p(typeof(expr), unsigned short) || \ - __builtin_types_compatible_p(typeof(expr), const unsigned short) || \ - __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \ - __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \ - (unsigned short)1, \ - (expr)+0)))))) - #ifndef __ATOMIC_RELAXED #error "Expecting C11 atomic ops" #endif diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h index c797f0d457..554c5ce7df 100644 --- a/include/qemu/compiler.h +++ b/include/qemu/compiler.h @@ -227,4 +227,50 @@ #define SECOND_ARG(first, second, ...) second #define IS_EMPTY_(junk_maybecomma) SECOND_ARG(junk_maybecomma 1, 0) +#ifndef __cplusplus +/* + * Useful in macros that need to declare temporary variables. For example, + * the variable that receives the old value of an atomically-accessed + * variable must be non-qualified, because atomic builtins return values + * through a pointer-type argument as in __atomic_load(&var, &old, MODEL). + * + * This macro has to handle types smaller than int manually, because of + * implicit promotion. int and larger types, as well as pointers, can be + * converted to a non-qualified type just by applying a binary operator. + */ +#define typeof_strip_qual(expr) \ + typeof( \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), bool) || \ + __builtin_types_compatible_p(typeof(expr), const bool) || \ + __builtin_types_compatible_p(typeof(expr), volatile bool) || \ + __builtin_types_compatible_p(typeof(expr), const volatile bool), \ + (bool)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), signed char) || \ + __builtin_types_compatible_p(typeof(expr), const signed char) || \ + __builtin_types_compatible_p(typeof(expr), volatile signed char) || \ + __builtin_types_compatible_p(typeof(expr), const volatile signed char), \ + (signed char)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), unsigned char) || \ + __builtin_types_compatible_p(typeof(expr), const unsigned char) || \ + __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \ + __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \ + (unsigned char)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), signed short) || \ + __builtin_types_compatible_p(typeof(expr), const signed short) || \ + __builtin_types_compatible_p(typeof(expr), volatile signed short) || \ + __builtin_types_compatible_p(typeof(expr), const volatile signed short), \ + (signed short)1, \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(typeof(expr), unsigned short) || \ + __builtin_types_compatible_p(typeof(expr), const unsigned short) || \ + __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \ + __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \ + (unsigned short)1, \ + (expr)+0)))))) +#endif + #endif /* COMPILER_H */