Switch to libbsd-overlay

This is more portable than libbsd as everything Just Works, even on BSD systems,
and is the recommended method of consuming libbsd nowadays.

It also helpfully lets things work with glibc-provided functions for new
enough glibc.

[For the 21.1.x backport, take inspiration from @alanc's commit to libxdmcp
at c01da8ebd0.]

Closes: https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/973
Co-authored-by: Guillem Jover <guillem@hadrons.org>
(cherry picked from commit 94945a5274)
Signed-off-by: Sam James <sam@gentoo.org>

configure.ac

@@ -164,8 +164,16 @@ AC_REPLACE_FUNCS([reallocarray strcasecmp strcasestr strlcat strlcpy strndup\
 	timingsafe_memcmp])
 AM_CONDITIONAL(POLL, [test "x$ac_cv_func_poll" = "xyes"])
 
-AC_CHECK_LIB([bsd], [arc4random_buf])
-AC_CHECK_FUNCS([arc4random_buf])
+# Checks for non-standard functions and fallback to libbsd if we can
+# We only check for arc4random_buf, because if we have that, we don't
+# need/use getentropy.
+AC_LINK_IFELSE([AC_LANG_CALL([], [arc4random_buf])],
+               [TRY_LIBBSD="no"], [TRY_LIBBSD="yes"])
+AS_IF([test "x$TRY_LIBBSD" = "xyes"],
+      [PKG_CHECK_MODULES([LIBBSD], [libbsd-overlay], [
+	CFLAGS="$CFLAGS $LIBBSD_CFLAGS"
+	LIBS="$LIBS $LIBBSD_LIBS"
+], [:])])
 
 AC_CHECK_DECLS([program_invocation_short_name], [], [], [[#include <errno.h>]])
 

include/os.h

@@ -50,16 +50,13 @@ SOFTWARE.
 #include "misc.h"
 #include <stdarg.h>
 #include <stdint.h>
+#if defined(HAVE_REALLOCARRAY)
+#include <stdlib.h>       /* for reallocarray */
+#endif
 #include <string.h>
 #ifdef MONOTONIC_CLOCK
 #include <time.h>
 #endif
-#if defined(HAVE_LIBBSD) && defined(HAVE_REALLOCARRAY)
-#include <bsd/stdlib.h>       /* for reallocarray */
-#endif
-#if defined(HAVE_LIBBSD) && defined(HAVE_STRLCPY)
-#include <bsd/string.h>       /* for strlcpy, strlcat */
-#endif
 
 #define SCREEN_SAVER_ON   0
 #define SCREEN_SAVER_OFF  1

meson.build

@@ -96,7 +96,7 @@ applewmproto_dep = dependency('applewmproto', version: '>= 1.4', fallback: ['xor
 xshmfence_dep = dependency('xshmfence', version: '>= 1.1', required: false)
 
 pixman_dep = dependency('pixman-1')
-libbsd_dep = dependency('libbsd', required: false)
+libbsd_dep = dependency('libbsd-overlay', required: false)
 xkbcomp_dep = dependency('xkbcomp', required: false)
 xkbfile_dep = dependency('xkbfile')
 xfont2_dep = dependency('xfont2', version: '>= 2.0')

os/auth.c

@@ -46,9 +46,7 @@ from The Open Group.
 #ifdef WIN32
 #include    <X11/Xw32defs.h>
 #endif
-#ifdef HAVE_LIBBSD
-#include   <bsd/stdlib.h>       /* for arc4random_buf() */
-#endif
+#include   <stdlib.h>       /* for arc4random_buf() */
 
 struct protocol {
     unsigned short name_length;