[tracker] configure: Check that sqlite3 has sqlite3_auto_extension() enabled

[Carlos Garnacho <carlosg src gnome org>]

commit f3db8b289136e7be384505c85778fe22fc18df2d
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Mar 27 14:22:21 2016 +0200

    configure: Check that sqlite3 has sqlite3_auto_extension() enabled
    
    Only do this if we need to load the FTS5 module, sqlite3 might have
    been compiled with SQLITE_OMIT_LOAD_EXTENSION, which will make things
    go very wrong (poking NULL vfuncs in a 0'ed out sqlite3_api_routines)
    at runtime.
    
    This facility must be enabled if we need to load our FTS module, so
    bail out at configure time if it's not there.

 configure.ac                |    6 ++++++
 m4/sqlite-auto-extension.m4 |   40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c5a006e..6bd6d93 100644
--- a/configure.ac
+++ b/configure.ac
@@ -831,6 +831,12 @@ if test "x$have_tracker_fts" = "xyes"; then
       AC_DEFINE(HAVE_BUILTIN_FTS, [], [Defined if Sqlite has FTS5 compiled in])
    else
       have_builtin_fts5="no"
+
+      # Make sure SQLite has extension loading enabled
+      AX_SQLITE_AUTO_EXTENSION
+      if test "x$ax_cv_sqlite_auto_extension" != "xyes"; then
+        AC_MSG_ERROR([sqlite3 cannot load extensions])
+      fi
    fi
 else
    AC_DEFINE(HAVE_TRACKER_FTS, [0], [Define to 0 if tracker FTS is not compiled])
diff --git a/m4/sqlite-auto-extension.m4 b/m4/sqlite-auto-extension.m4
new file mode 100644
index 0000000..60cee93
--- /dev/null
+++ b/m4/sqlite-auto-extension.m4
@@ -0,0 +1,40 @@
+AC_DEFUN([AX_SQLITE_AUTO_EXTENSION],
+[
+  AC_REQUIRE([AC_PROG_CC])
+
+  OLD_CFLAGS="$CFLAGS"
+  OLD_LDFLAGS="$LDFLAGS"
+  OLD_LIBS="$LIBS"
+  CFLAGS="$SQLITE3_CFLAGS"
+  LDFLAGS="$SQLITE3_LDFLAGS"
+  LIBS="$SQLITE3_LIBS"
+
+  AC_CHECK_HEADERS([sqlite3.h])
+
+  AC_CACHE_CHECK([whether SQLite3 has extension loading enabled],
+                 [ax_cv_sqlite_auto_extension],
+  [
+  AC_RUN_IFELSE(
+    [AC_LANG_PROGRAM([[#include <sqlite3.h>
+                       static int initialized = 0;
+                       int extEntryPoint(sqlite3 *db, const char **err, void **api){
+                         initialized = 1;
+                         if (api != 0 && *api != 0)
+                           return SQLITE_OK;
+                         return SQLITE_ERROR;
+                       }]],
+                     [[sqlite3 *db;
+                       int rc;
+                       sqlite3_auto_extension((void (*)(void))extEntryPoint);
+                       rc = sqlite3_open(":memory:", &db);
+                       if (rc!=SQLITE_OK) return -1;
+                       if (initialized==0) return -1]])],
+    [ax_cv_sqlite_auto_extension=yes],
+    [ax_cv_sqlite_auto_extension=no],
+    [ax_cv_sqlite_auto_extension=no])])
+
+  CFLAGS="$OLD_CFLAGS"
+  LDFLAGS="$OLD_LDFLAGS"
+  LIBS="$OLD_LIBS"
+])
+