Could not load Spatialite extension in QT5.9

MCA4213

Hi, I am trying to load Spatialite as extension in Qt, I have done that before with Qt4.8, but I failed with the QT5.9.
I changed the sqlite.pri by removing "SQLITE_OMIT_LOAD_EXTENSION", and I did some change on the sqlite.c by removing the "#define SQLITE_OMIT_LOAD_EXTENSION 1", and adding "#define SQLITE_ENABLE_LOAD_EXTENSION 1".
I also add the following lines to openDatabase(....):
#if defined(SQLITE_ENABLE_LOAD_EXTENSION)
| SQLITE_LoadExtension|SQLITE_LoadExtFunc
#endif

Now the "requet.setQuery("SELECT load_extension('spatialite')", dbProject);" function is recognized, but I got this message:
error "The specified procedure could not be found.\r\nUnable to fetch row"
If I take a look on my debug output in MSVC14, I can see that the spatialite.dll and all its dependencies are loaded.

Notice: I tested this with my Spatialite and also the mod_spatialite that I download form their website.

Any ideas about this problem?
Thanks in advance.

MCA4213

The problem was with my compiled library (still i don't know why?), and also with the mod_spatialite that I downloaded. This last one when we use it with the visual studio need a replacement for the libstdc++_64-6.dll because it will cause crash.

My problem was here, the one that I used was not the good one, and was causing the The specified procedure could not be found, so I downloaded the x86_64-5.3.0-release-win32-seh-rt_v4-rev0 and I used the libstdc++-6.dll (I changed the name to libstdc++_64-6.dll) with the libgcc_s_seh-1.dll. I also changed the libxml2-2.dll with another one that I compiled before.

Then I changed the qSqlite pluginn as follow:

open the "Qt5.9.0\5.9\Src\qtbase\src\3rdparty\sqlite" folder and change the sqlite3.c as following:

1- comment or remove the "#define SQLITE_OMIT_LOAD_EXTENSION 1"

2-add:

#ifndef SQLITE_ENABLE_LOAD_EXTENSION
#define SQLITE_ENABLE_LOAD_EXTENSION 1
#endif

3- go the "static int openDatabase( const char *zFilename,sqlite3 **ppDb, unsigned int flags, const char *zVfs)" function and add "| SQLITE_LoadExtFunc" to SQLITE_ENABLE_LOAD_EXTENSION as following:

#ifdef SQLITE_ENABLE_LOAD_EXTENSION
                 | SQLITE_LoadExtension | SQLITE_LoadExtFunc
#endif

compile your plugin again using your compiler ( nmake in my case) in Qt5.9.0\5.9\Src\qtbase\src\plugins\sqldrivers\sqlite\sqlite.pro
call the following code to load your spatialite:

QSqlQueryModel sql;
sql.setQuery("SELECT load_extension('mod_spatialite')", db);

Ferni

Hi @MCA4213 ! I'm trying to do exactly the same but for Android. I was struggling to compile qSqlite plugin. I followed all your steps and now I have my qSqlite plugin well compiled.

I took from here a precompiled spatialite version for Android and then in Qt I run

QSqlQuery spatialiteSqlQuery(db);
spatialiteSqlQuery.prepare("SELECT load_extension(\"libjsqlite\")");

but I'm still getting an error and I cannot load spatialite extension.

QSqlError("1", "Unable to fetch row", "not authorized")

Could you give me some help? Am I doing something wrong?

Thanks,
Fernando

MCA4213

@Ferni , I don't have experiance on android, but :
did you make the changes on the sqlite3 file ( in my case sqlite3.c)? by removing the omit definition and altering the enable extension by:" | SQLITE_LoadExtFunc" (change the existing one)?
The not authorized error is generated when the omit definition is enabled, or the SQLITE_LoadExtFunc has not been added.
you can find some other details on my discussion on the stackoverflow: [https://stackoverflow.com/questions/44427868/could-not-load-spatialite-extension-in-qsqlite-qt-5-9](link url)

Ferni

hey @MCA4213 , thanks!! I'm pretty sure that I set all the corresponding flags but I will check again.