compat: Linux getauxval() replacement

This was added over a decade ago, but 🤷...

compat/getauxval.c

@@ -0,0 +1,43 @@
+/*****************************************************************************
+ * getauxval.c: Linux getauxval() replacement
+ *****************************************************************************
+ * Copyright © 2022 Rémi Denis-Courmont
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stddef.h>
+
+extern char **environ;
+
+unsigned long getauxval(unsigned long type)
+{
+	const unsigned long *auxv;
+	size_t i = 0;
+
+	while (environ[i++] != NULL);
+
+	auxv = (const void *)&environ[i];
+
+	for (i = 0; auxv[i]; i += 2)
+		if (auxv[i] == type)
+			return auxv[i + 1];
+
+	return 0;
+}

configure.ac

@@ -734,6 +734,7 @@ dnl Check for non-standard system calls
 case "$SYS" in
   "linux")
     AC_CHECK_FUNCS([eventfd vmsplice sched_getaffinity recvmmsg memfd_create])
+    AC_REPLACE_FUNCS([getauxval])
     ;;
   "mingw32")
     AC_CHECK_FUNCS([_lock_file])

include/vlc_fixups.h

@@ -503,6 +503,11 @@ void *lfind( const void *key, const void *base, size_t *nmemb,
 void tdestroy( void *root, void (*free_node)(void *nodep) );
 #endif
 
+/* sys/auxv.h */
+#ifndef HAVE_GETAUXVAL
+unsigned long getauxval(unsigned long);
+#endif
+
 /* Random numbers */
 #ifndef HAVE_NRAND48
 double erand48 (unsigned short subi[3]);