foo.diff

diff --git a/configure.ac b/configure.ac
index 3cb187b..a567b6d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -952,6 +952,35 @@ if test "x$have_zstd" = "xyes"; then
     AC_DEFINE(HAVE_ZSTD,1,[Have Zstd])
     TOR_ZSTD_CFLAGS="${ZSTD_CFLAGS}"
     TOR_ZSTD_LIBS="${ZSTD_LIBS}"
+
+    save_LIBS="$LIBS"
+    save_LDFLAGS="$LDFLAGS"
+
+    LIBS="$TOR_ZSTD_LIBS $LIBS"
+    LDFLAGS="$TOR_ZSTD_LIBS $LDFLAGS"
+
+    AC_MSG_CHECKING([whether we can link against libzstd])
+    AC_LINK_IFELSE([AC_LANG_SOURCE([[
+                        #include <stdio.h>
+                        #include <zstd.h>
+                        int main(int argc, char **argv)
+                        {
+                          size_t v = ZSTD_versionNumber();
+                          printf("%d.%d.%d", (int)v / 10000 % 100,
+                                             (int)v / 100 % 100,
+                                             (int)v % 100);
+                          return 0;
+                        }
+                   ]], [$TOR_ZSTD_CFLAGS $TOR_ZSTD_LIBS])],
+                   [zstd_linkable=yes; AC_MSG_RESULT([yes])],
+                   [zstd_linkable=no; AC_MSG_RESULT([no])])
+
+    if test "x$zstd_linkable" = "xno" ; then
+        AC_MSG_ERROR([Unable to link against libzstd.])
+    fi
+
+    LIBS="$save_LIBS"
+    LDFLAGS="$save_LDFLAGS"
 fi
 AC_SUBST(TOR_ZSTD_CFLAGS)
 AC_SUBST(TOR_ZSTD_LIBS)