Rename several printf attributes declarations to __printf__

For kernel builds on FreeBSD, we redefine `__printf__` to
`__freebsd_kprintf__`, to support FreeBSD kernel printf(9) extensions
with clang.

In OpenZFS various printf related functions are declared with
`__attribute__((format(printf, X, Y)))`, so these won't work with the
above redefinition. With clang 21 and higher, this leads to errors
similar to:

    sys/contrib/openzfs/module/zfs/spa_misc.c:414:38: error: passing
    'printf' format string where 'freebsd_kprintf' format string is
    expected [-Werror,-Wformat]
      414 |         (void) vsnprintf(buf, sizeof (buf), fmt, adx);
          |                                             ^

Since attribute names can always be spelled with leading and trailing
double underscores, rename these instances.

Note that in the FreeBSD base system we usually use `__printflike` from
`<sys/cdefs.h>`, but that does not apply to OpenZFS.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Dimitry Andric <dimitry@andric.com>
Closes openzfs#18095

Author: DimitryAndric

include/os/freebsd/spl/sys/cmn_err.h

@@ -52,28 +52,28 @@ extern "C" {
 #ifndef _ASM
 
 extern void cmn_err(int, const char *, ...)
-    __attribute__((format(printf, 2, 3)));
+    __attribute__((format(__printf__, 2, 3)));
 
 extern void vzcmn_err(zoneid_t, int, const char *, __va_list)
-    __attribute__((format(printf, 3, 0)));
+    __attribute__((format(__printf__, 3, 0)));
 
 extern void vcmn_err(int, const char *, __va_list)
-    __attribute__((format(printf, 2, 0)));
+    __attribute__((format(__printf__, 2, 0)));
 
 extern void zcmn_err(zoneid_t, int, const char *, ...)
-    __attribute__((format(printf, 3, 4)));
+    __attribute__((format(__printf__, 3, 4)));
 
 extern void vzprintf(zoneid_t, const char *, __va_list)
-    __attribute__((format(printf, 2, 0)));
+    __attribute__((format(__printf__, 2, 0)));
 
 extern void zprintf(zoneid_t, const char *, ...)
-    __attribute__((format(printf, 2, 3)));
+    __attribute__((format(__printf__, 2, 3)));
 
 extern void vuprintf(const char *, __va_list)
-    __attribute__((format(printf, 1, 0)));
+    __attribute__((format(__printf__, 1, 0)));
 
 extern void panic(const char *, ...)
-    __attribute__((format(printf, 1, 2), __noreturn__));
+    __attribute__((format(__printf__, 1, 2), __noreturn__));
 
 #define	cmn_err_once(ce, ...)				\
 do {							\

include/os/freebsd/spl/sys/kmem.h

@@ -55,9 +55,9 @@ MALLOC_DECLARE(M_SOLARIS);
 typedef struct vmem vmem_t;
 
 extern char	*kmem_asprintf(const char *, ...)
-    __attribute__((format(printf, 1, 2)));
+    __attribute__((format(__printf__, 1, 2)));
 extern char *kmem_vasprintf(const char *fmt, va_list ap)
-    __attribute__((format(printf, 1, 0)));
+    __attribute__((format(__printf__, 1, 0)));
 
 extern int kmem_scnprintf(char *restrict str, size_t size,
     const char *restrict fmt, ...);

include/sys/spa.h

@@ -1127,9 +1127,9 @@ extern void spa_set_allocator(spa_t *spa, const char *allocator);
 
 /* Miscellaneous support routines */
 extern void spa_load_failed(spa_t *spa, const char *fmt, ...)
-    __attribute__((format(printf, 2, 3)));
+    __attribute__((format(__printf__, 2, 3)));
 extern void spa_load_note(spa_t *spa, const char *fmt, ...)
-    __attribute__((format(printf, 2, 3)));
+    __attribute__((format(__printf__, 2, 3)));
 extern void spa_activate_mos_feature(spa_t *spa, const char *feature,
     dmu_tx_t *tx);
 extern void spa_deactivate_mos_feature(spa_t *spa, const char *feature);

include/sys/vdev.h

@@ -54,7 +54,7 @@ extern int zfs_nocacheflush;
 typedef boolean_t vdev_open_children_func_t(vdev_t *vd);
 
 extern void vdev_dbgmsg(vdev_t *vd, const char *fmt, ...)
-    __attribute__((format(printf, 2, 3)));
+    __attribute__((format(__printf__, 2, 3)));
 extern void vdev_dbgmsg_print_tree(vdev_t *, int);
 extern int vdev_open(vdev_t *);
 extern void vdev_open_children(vdev_t *);

include/sys/zfs_debug.h

@@ -68,7 +68,7 @@ extern int zfs_dbgmsg_enable;
 extern void __set_error(const char *file, const char *func, int line, int err);
 extern void __zfs_dbgmsg(char *buf);
 extern void __dprintf(boolean_t dprint, const char *file, const char *func,
-    int line, const char *fmt, ...)  __attribute__((format(printf, 5, 6)));
+    int line, const char *fmt, ...)  __attribute__((format(__printf__, 5, 6)));
 
 /*
  * Some general principles for using zfs_dbgmsg():