Fix a weird problem with lib6 versioned symbols.

configure.ac

@@ -178,6 +178,9 @@ AC_TRY_COMPILE([],
  [AC_MSG_RESULT(no)])
 AC_DEFINE_UNQUOTED(ATTRIBUTE_PRINTF(x,y), $ac_v_attribute_printf, [Define to the __printf__ attribute if present])
 
+AC_CHECK_LIB(dl, dladdr,
+ [AC_DEFINE(HAVE_DLADDR, 1, Define to 1 if you have the `dladdr' function.)])
+
 AC_CHECK_LIB(m, log, [MATH_LIBS="-lm"])
 AC_SUBST(MATH_LIBS)
 AC_CHECK_LIB(dl, dlopen, [DL_LIBS="-ldl"])

msvc/config.h

@@ -28,6 +28,7 @@
 #define HAVE_CONNECT 1
 #define HAVE_CREATEFILEA 1
 #define HAVE_CREATEFILEW 1
+/* #undef HAVE_DLADDR */
 /* #undef HAVE_DLFCN_H */
 #define HAVE_DUP 1
 #define HAVE_DUP2 1

src/libzzuf/lib-fd.c

@@ -20,8 +20,6 @@
 
 #include "config.h"
 
-/* Need this for RTLD_NEXT */
-#define _GNU_SOURCE
 /* Use this to get lseek64() on glibc systems */
 #define _LARGEFILE64_SOURCE
 /* Use this to get off64_t() on Solaris systems */

src/libzzuf/lib-load.h

@@ -29,7 +29,8 @@
                  * otherwise we may miss a lot of stuff if we wait for \
                  * the linker to load us fully. */ \
                 _zz_init(); \
-                ORIG(x) = dlsym(RTLD_NEXT, STR(x)); \
+                extern void *_zz_dl_lib; \
+                ORIG(x) = dlsym(_zz_dl_lib, STR(x)); \
             } \
             if(!ORIG(x)) \
                 abort(); \

src/libzzuf/lib-mem.c

@@ -16,7 +16,7 @@
 
 #include "config.h"
 
-/* Need this for RTLD_NEXT */
+/* Need this for off64_t */
 #define _GNU_SOURCE
 /* Need this for MAP_ANON and valloc() on FreeBSD (together with cdefs.h) */
 #define _BSD_SOURCE

src/libzzuf/sys.c

@@ -16,12 +16,19 @@
 
 #include "config.h"
 
+/* Need this for RTLD_NEXT */
+#define _GNU_SOURCE
+
 #if defined HAVE_STDINT_H
 #   include <stdint.h>
 #elif defined HAVE_INTTYPES_H
 #   include <inttypes.h>
 #endif
 
+#ifdef HAVE_DLFCN_H
+#   include <dlfcn.h>
+#endif
+
 #if defined HAVE_WINDOWS_H
 #   include <windows.h>
 #   include <imagehlp.h>
@@ -35,6 +42,10 @@
 #include "sys.h"
 #include "lib-load.h"
 
+#if defined HAVE_DLFCN_H
+void *_zz_dl_lib = RTLD_NEXT;
+#endif
+
 #if defined HAVE_WINDOWS_H
 static void insert_funcs(void *);
 
@@ -77,6 +88,20 @@ void _zz_sys_init(void)
         insert_funcs(entry.hModule);
     }
     CloseHandle(list);
+#elif defined HAVE_DLFCN_H
+    /* If glibc is recent enough, we use dladdr() to get its address. This
+     * way we are sure that the symbols we load are the most recent version,
+     * or we may get weird problems. We choose fileno as a random symbol to
+     * get, because we know we don't divert it. */
+#   if HAVE_DLADDR
+    Dl_info di;
+    if (dladdr(&fileno, &di) != 0)
+    {
+        void *lib = dlopen(di.dli_fname, RTLD_NOW);
+        if (lib)
+            _zz_dl_lib = lib;
+    }
+#   endif
 #else
     /* Nothing to do on our platform */
 #endif