build-sys: check for mallinfo

mallinfo is not specified by POSIX or the C standards, therefore
it's not available for all libc libraries (musl).

Add the ability to disable mallinfo statistics.

Fixes:
selinux-util.c: In function ‘mac_selinux_init’:
selinux-util.c:70:25: error: storage size of ‘before_mallinfo’ isn’t known
         struct mallinfo before_mallinfo, after_mallinfo;

Signed-off-by: Romain Naour <romain.naour@openwide.fr>

configure.ac

@@ -223,6 +223,9 @@ else
 fi
 AC_SUBST(sushell)
 
+# selinux-util.c uses struct mallinfo which is not available for all C libraries (musl).
+AC_CHECK_FUNCS([mallinfo])
+
 # ------------------------------------------------------------------------------
 
 AC_CHECK_DECL([unshare],

src/shared/selinux-util.c

@@ -67,15 +67,21 @@ int mac_selinux_init(const char *prefix) {
 
 #ifdef HAVE_SELINUX
         usec_t before_timestamp, after_timestamp;
+
+#ifdef HAVE_MALLINFO
         struct mallinfo before_mallinfo, after_mallinfo;
+#endif
 
         if (!mac_selinux_use())
                 return 0;
 
         if (label_hnd)
                 return 0;
 
+#ifdef HAVE_MALLINFO
         before_mallinfo = mallinfo();
+#endif
+
         before_timestamp = now(CLOCK_MONOTONIC);
 
         if (prefix) {
@@ -92,16 +98,25 @@ int mac_selinux_init(const char *prefix) {
                 r = security_getenforce() == 1 ? -errno : 0;
         } else  {
                 char timespan[FORMAT_TIMESPAN_MAX];
+
+#ifdef HAVE_MALLINFO
                 int l;
+#endif
 
                 after_timestamp = now(CLOCK_MONOTONIC);
+
+#ifdef HAVE_MALLINFO
                 after_mallinfo = mallinfo();
 
                 l = after_mallinfo.uordblks > before_mallinfo.uordblks ? after_mallinfo.uordblks - before_mallinfo.uordblks : 0;
 
                 log_debug("Successfully loaded SELinux database in %s, size on heap is %iK.",
                           format_timespan(timespan, sizeof(timespan), after_timestamp - before_timestamp, 0),
                           (l+1023)/1024);
+#else
+                log_debug("Successfully loaded SELinux database in %s",
+                          format_timespan(timespan, sizeof(timespan), after_timestamp - before_timestamp, 0));
+#endif
         }
 #endif