tree-wide: use __ prefixed gcc attributes (#10843)

As suggest here:

https://gcc.gnu.org/onlinedocs/gcc/Attribute-Syntax.html#Attribute-Syntax

    "You may optionally specify attribute names with ‘__’ preceding and
    following the name. This allows you to use them in header files without
    being concerned about a possible macro of the same name. For example,
    you may use the attribute name __noreturn__ instead of noreturn. "

src/basic/json.h

@@ -274,7 +274,7 @@ int json_log_internal(JsonVariant *variant, int level, int error, const char *fi
 
 #define _JSON_VARIANT_STRING_CONST(xq, x)                                       \
         ({                                                              \
-                __attribute__((aligned(2))) static const char UNIQ_T(json_string_const, xq)[] = (x); \
+                __attribute__((__aligned__(2))) static const char UNIQ_T(json_string_const, xq)[] = (x); \
                 assert((((uintptr_t) UNIQ_T(json_string_const, xq)) & 1) == 0); \
                 (JsonVariant*) ((uintptr_t) UNIQ_T(json_string_const, xq) + 1); \
         })

src/basic/macro.h

@@ -8,30 +8,30 @@
 #include <sys/sysmacros.h>
 #include <sys/types.h>
 
-#define _printf_(a, b) __attribute__ ((format (printf, a, b)))
+#define _printf_(a, b) __attribute__ ((__format__(printf, a, b)))
 #ifdef __clang__
 #  define _alloc_(...)
 #else
-#  define _alloc_(...) __attribute__ ((alloc_size(__VA_ARGS__)))
+#  define _alloc_(...) __attribute__ ((__alloc_size__(__VA_ARGS__)))
 #endif
-#define _sentinel_ __attribute__ ((sentinel))
-#define _unused_ __attribute__ ((unused))
-#define _destructor_ __attribute__ ((destructor))
-#define _pure_ __attribute__ ((pure))
-#define _const_ __attribute__ ((const))
-#define _deprecated_ __attribute__ ((deprecated))
-#define _packed_ __attribute__ ((packed))
-#define _malloc_ __attribute__ ((malloc))
-#define _weak_ __attribute__ ((weak))
+#define _sentinel_ __attribute__ ((__sentinel__))
+#define _unused_ __attribute__ ((__unused__))
+#define _destructor_ __attribute__ ((__destructor__))
+#define _pure_ __attribute__ ((__pure__))
+#define _const_ __attribute__ ((__const__))
+#define _deprecated_ __attribute__ ((__deprecated__))
+#define _packed_ __attribute__ ((__packed__))
+#define _malloc_ __attribute__ ((__malloc__))
+#define _weak_ __attribute__ ((__weak__))
 #define _likely_(x) (__builtin_expect(!!(x), 1))
 #define _unlikely_(x) (__builtin_expect(!!(x), 0))
-#define _public_ __attribute__ ((visibility("default")))
-#define _hidden_ __attribute__ ((visibility("hidden")))
-#define _weakref_(x) __attribute__((weakref(#x)))
-#define _alignas_(x) __attribute__((aligned(__alignof(x))))
-#define _cleanup_(x) __attribute__((cleanup(x)))
+#define _public_ __attribute__ ((__visibility__("default")))
+#define _hidden_ __attribute__ ((__visibility__("hidden")))
+#define _weakref_(x) __attribute__((__weakref__(#x)))
+#define _alignas_(x) __attribute__((__aligned__(__alignof(x))))
+#define _cleanup_(x) __attribute__((__cleanup__(x)))
 #if __GNUC__ >= 7
-#define _fallthrough_ __attribute__((fallthrough))
+#define _fallthrough_ __attribute__((__fallthrough__))
 #else
 #define _fallthrough_
 #endif
@@ -41,7 +41,7 @@
 #if __STDC_VERSION__ >= 201112L
 #define _noreturn_ _Noreturn
 #else
-#define _noreturn_ __attribute__((noreturn))
+#define _noreturn_ __attribute__((__noreturn__))
 #endif
 #endif
 

src/basic/sparse-endian.h

@@ -27,8 +27,8 @@
 #include <stdint.h>
 
 #ifdef __CHECKER__
-#define __sd_bitwise __attribute__((bitwise))
-#define __sd_force __attribute__((force))
+#define __sd_bitwise __attribute__((__bitwise__))
+#define __sd_force __attribute__((__force__))
 #else
 #define __sd_bitwise
 #define __sd_force

src/basic/unaligned.h

@@ -7,37 +7,37 @@
 /* BE */
 
 static inline uint16_t unaligned_read_be16(const void *_u) {
-        const struct __attribute__((packed, may_alias)) { uint16_t x; } *u = _u;
+        const struct __attribute__((__packed__, __may_alias__)) { uint16_t x; } *u = _u;
 
         return be16toh(u->x);
 }
 
 static inline uint32_t unaligned_read_be32(const void *_u) {
-        const struct __attribute__((packed, may_alias)) { uint32_t x; } *u = _u;
+        const struct __attribute__((__packed__, __may_alias__)) { uint32_t x; } *u = _u;
 
         return be32toh(u->x);
 }
 
 static inline uint64_t unaligned_read_be64(const void *_u) {
-        const struct __attribute__((packed, may_alias)) { uint64_t x; } *u = _u;
+        const struct __attribute__((__packed__, __may_alias__)) { uint64_t x; } *u = _u;
 
         return be64toh(u->x);
 }
 
 static inline void unaligned_write_be16(void *_u, uint16_t a) {
-        struct __attribute__((packed, may_alias)) { uint16_t x; } *u = _u;
+        struct __attribute__((__packed__, __may_alias__)) { uint16_t x; } *u = _u;
 
         u->x = be16toh(a);
 }
 
 static inline void unaligned_write_be32(void *_u, uint32_t a) {
-        struct __attribute__((packed, may_alias)) { uint32_t x; } *u = _u;
+        struct __attribute__((__packed__, __may_alias__)) { uint32_t x; } *u = _u;
 
         u->x = be32toh(a);
 }
 
 static inline void unaligned_write_be64(void *_u, uint64_t a) {
-        struct __attribute__((packed, may_alias)) { uint64_t x; } *u = _u;
+        struct __attribute__((__packed__, __may_alias__)) { uint64_t x; } *u = _u;
 
         u->x = be64toh(a);
 }
@@ -45,37 +45,37 @@ static inline void unaligned_write_be64(void *_u, uint64_t a) {
 /* LE */
 
 static inline uint16_t unaligned_read_le16(const void *_u) {
-        const struct __attribute__((packed, may_alias)) { uint16_t x; } *u = _u;
+        const struct __attribute__((__packed__, __may_alias__)) { uint16_t x; } *u = _u;
 
         return le16toh(u->x);
 }
 
 static inline uint32_t unaligned_read_le32(const void *_u) {
-        const struct __attribute__((packed, may_alias)) { uint32_t x; } *u = _u;
+        const struct __attribute__((__packed__, __may_alias__)) { uint32_t x; } *u = _u;
 
         return le32toh(u->x);
 }
 
 static inline uint64_t unaligned_read_le64(const void *_u) {
-        const struct __attribute__((packed, may_alias)) { uint64_t x; } *u = _u;
+        const struct __attribute__((__packed__, __may_alias__)) { uint64_t x; } *u = _u;
 
         return le64toh(u->x);
 }
 
 static inline void unaligned_write_le16(void *_u, uint16_t a) {
-        struct __attribute__((packed, may_alias)) { uint16_t x; } *u = _u;
+        struct __attribute__((__packed__, __may_alias__)) { uint16_t x; } *u = _u;
 
         u->x = le16toh(a);
 }
 
 static inline void unaligned_write_le32(void *_u, uint32_t a) {
-        struct __attribute__((packed, may_alias)) { uint32_t x; } *u = _u;
+        struct __attribute__((__packed__, __may_alias__)) { uint32_t x; } *u = _u;
 
         u->x = le32toh(a);
 }
 
 static inline void unaligned_write_le64(void *_u, uint64_t a) {
-        struct __attribute__((packed, may_alias)) { uint64_t x; } *u = _u;
+        struct __attribute__((__packed__, __may_alias__)) { uint64_t x; } *u = _u;
 
         u->x = le64toh(a);
 }

src/basic/util.h

@@ -172,7 +172,8 @@ static inline void _reset_errno_(int *saved_errno) {
         errno = *saved_errno;
 }
 
-#define PROTECT_ERRNO _cleanup_(_reset_errno_) __attribute__((unused)) int _saved_errno_ = errno
+#define PROTECT_ERRNO                                                   \
+        _cleanup_(_reset_errno_) __attribute__((__unused__)) int _saved_errno_ = errno
 
 static inline int negative_errno(void) {
         /* This helper should be used to shut up gcc if you know 'errno' is