mallinfo-util: assume mallinfo() exists

The check existed for musl. Let's remove it, as we explicitly request glibc.

While removing the check, this also drops generic_mallinfo, introduces
a tiny converter from struct mallinfo to struct mallinfo2 if mallinfo2()
does not exist, and renames mallinfo-util.h to malloc.h.

With this change, we can drop many ifdefs and casts in .c files.

src/shared/selinux-util.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include <fcntl.h>
+#include <malloc.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
@@ -20,7 +21,6 @@
 #include "label.h"
 #include "label-util.h"
 #include "log.h"
-#include "mallinfo-util.h"
 #include "path-util.h"
 #include "selinux-util.h"
 #include "string-util.h"
@@ -106,14 +106,10 @@ static int open_label_db(void) {
         struct selabel_handle *hnd;
         /* Avoid maybe-uninitialized false positives */
         usec_t before_timestamp = USEC_INFINITY, after_timestamp = USEC_INFINITY;
-#  if HAVE_GENERIC_MALLINFO
-        generic_mallinfo before_mallinfo = {};
-#  endif
+        struct mallinfo2 before_mallinfo = {};
 
         if (DEBUG_LOGGING) {
-#  if HAVE_GENERIC_MALLINFO
-                before_mallinfo = generic_mallinfo_get();
-#  endif
+                before_mallinfo = mallinfo2();
                 before_timestamp = now(CLOCK_MONOTONIC);
         }
 
@@ -123,16 +119,11 @@ static int open_label_db(void) {
 
         if (DEBUG_LOGGING) {
                 after_timestamp = now(CLOCK_MONOTONIC);
-#  if HAVE_GENERIC_MALLINFO
-                generic_mallinfo after_mallinfo = generic_mallinfo_get();
-                size_t l = LESS_BY((size_t) after_mallinfo.uordblks, (size_t) before_mallinfo.uordblks);
+                struct mallinfo2 after_mallinfo = mallinfo2();
+                size_t l = LESS_BY(after_mallinfo.uordblks, before_mallinfo.uordblks);
                 log_debug("Successfully loaded SELinux database in %s, size on heap is %zuK.",
                           FORMAT_TIMESPAN(after_timestamp - before_timestamp, 0),
                           DIV_ROUND_UP(l, 1024));
-#  else
-                log_debug("Successfully loaded SELinux database in %s.",
-                          FORMAT_TIMESPAN(after_timestamp - before_timestamp, 0));
-#  endif
         }
 
         /* release memory after measurement */