compat: restore posix_memalign()

aligned_alloc() is not portably suitable for over-alignments.
posix_memalign()/memalign() are still needed.

This essentially reverts commit 34cd965645.

compat/posix_memalign.c

@@ -0,0 +1,80 @@
+/*****************************************************************************
+ * posix_memalign.c: POSIX posix_memalign() replacement
+ *****************************************************************************
+ * Copyright © 2012, 2019 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 <errno.h>
+#include <stdlib.h>
+#include <limits.h>
+
+#ifdef HAVE_MEMALIGN
+# include <malloc.h>
+#else
+
+static void *memalign(size_t align, size_t size)
+{
+    void *p = malloc(size);
+
+    if ((uintptr_t)p & (align - 1)) {
+        free(p);
+        p = NULL;
+    }
+
+    return p;
+}
+
+#endif
+
+static int check_align(size_t align)
+{
+    if (align & (align - 1)) /* must be a power of two */
+        return EINVAL;
+    if (align < sizeof (void *)) /* must be a multiple of sizeof (void *) */
+        return EINVAL;
+    return 0;
+}
+
+int posix_memalign(void **ptr, size_t align, size_t size)
+{
+    int val = check_align(align);
+    if (val)
+        return val;
+
+    /* Unlike posix_memalign(), legacy memalign() requires that size be a
+     * multiple of align.
+     */
+    if (size > (SIZE_MAX / 2))
+        return ENOMEM;
+
+    size += (-size) & (align - 1);
+
+    int saved_errno = errno;
+    void *p = memalign(align, size);
+    if (p == NULL) {
+        val = errno;
+        errno = saved_errno;
+        return val;
+    }
+
+    *ptr = p;
+    return 0;
+}

configure.ac

@@ -633,8 +633,8 @@ dnl Check for system libs needed
 need_libc=false
 
 dnl Check for usual libc functions
-AC_CHECK_FUNCS([accept4 daemon fcntl flock fstatvfs fork getenv getpwuid_r isatty memalign mkostemp mmap open_memstream newlocale openat pipe2 pread posix_fadvise posix_madvise posix_memalign setlocale stricmp strnicmp strptime uselocale])
-AC_REPLACE_FUNCS([aligned_alloc atof atoll dirfd fdopendir flockfile fsync getdelim getpid lfind lldiv memrchr nrand48 poll recvmsg rewind sendmsg setenv strcasecmp strcasestr strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab tdestroy tfind timegm timespec_get strverscmp pathconf])
+AC_CHECK_FUNCS([accept4 daemon fcntl flock fstatvfs fork getenv getpwuid_r isatty memalign mkostemp mmap open_memstream newlocale openat pipe2 pread posix_fadvise posix_madvise setlocale stricmp strnicmp strptime uselocale])
+AC_REPLACE_FUNCS([aligned_alloc atof atoll dirfd fdopendir flockfile fsync getdelim getpid lfind lldiv memrchr nrand48 poll posix_memalign recvmsg rewind sendmsg setenv strcasecmp strcasestr strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab tdestroy tfind timegm timespec_get strverscmp pathconf])
 AC_REPLACE_FUNCS([gettimeofday])
 AC_CHECK_FUNC(fdatasync,,
   [AC_DEFINE(fdatasync, fsync, [Alias fdatasync() to fsync() if missing.])

include/vlc_fixups.h

@@ -90,6 +90,7 @@ typedef struct
 
 #if !defined (HAVE_ALIGNED_ALLOC) || \
     !defined (HAVE_MEMRCHR) || \
+    !defined (HAVE_POSIX_MEMALIGN) || \
     !defined (HAVE_QSORT_R) || \
     !defined (HAVE_STRLCPY) || \
     !defined (HAVE_STRNDUP) || \
@@ -299,6 +300,10 @@ int setenv (const char *, const char *, int);
 int unsetenv (const char *);
 #endif
 
+#ifndef HAVE_POSIX_MEMALIGN
+int posix_memalign(void **, size_t, size_t);
+#endif
+
 #ifndef HAVE_ALIGNED_ALLOC
 void *aligned_alloc(size_t, size_t);
 #endif