How are you building the DLL and the executable? Are they both
including a copy of sqlite3.obj? Or are you using a sqlite3.dll?
Peter
On 1/25/2016 9:16 AM, Igor Korot wrote:
> Hi, Peter,
>
> On Mon, Jan 25, 2016 at 10:50 AM, Peter Aronson <pbaronson at att.net> wrote:
>> Igor,
>>
>> You can't safely pass a SQLite handle between different SQL DLLs that way if
>> they're both built with their own copy of the amalgamation (or link to
>> things built with different copies). SQLite uses a handful of global
>> variables, but each DLL has its own copy of each of these global variables
>> and they can and will have different values, which can mess things up. I
>> ran into a version of this problem when I tried to load a 2nd DLL built with
>> its own copy of the sqlite3.c amalgamation. I fixed that by exposing the
>> SQLite3 entrypoints in the first DLL and linking the second DLL against it
>> so there was only one copy of the amalgamation used for that SQLite3 handle.
> The SQLite is built only once and with just one version of the code.
>
> Consider following pseudo-code:
>
> In DLL:
>
> BOOL APIENTRY DLLMain()
> {
> }
>
> extern "C" __declspec(dllexport) Database *CreateObject(Database *db)
> {
> db = new SQLiteDatabase();
> db->Connect();
> return db;
> }
>
> In the main application:
>
> mainframe.h:
>
> class MainFrame
> {
> public:
> MainFrame();
> ~MainFrame();
> void ConnectToDb();
> private:
> Database *m_db;
> };
>
> mainframe.cpp:
>
> void MainFrame::ConnectToDb()
> {
> Database *db = NULL;
> LoadLibrary();
> func = GetProcAddress();
> m_db = func( db );
> }
>
> MainFrame::~MainFrame()
> {
> delete m_db; // this is where the crash happens
> }
>
> The pointer address are the same in DLL and main application MainFrame class.
> And as I said the crash occurs when it tries to acquire the mutex lock.
>
> Thank you.
>
>> Peter
>>
>>
>>
>>
>> On 1/24/2016 10:18 PM, Igor Korot wrote:
>>> Hi, ALL,
>>> I have a strange problem.
>>>
>>> I am trying to use sqlite in my program. It has a main application and
>>> couplef DLLs.
>>>
>>> I am getting the connection in one of the DLL, then the pointer is passed
>>> up
>>> to the main application.
>>>
>>> Upon exiting from the application I'm trying to close the connection and
>>> delete all the memory.
>>>
>>> Unfortunately upon exiting the application it crashes inside
>>> sqlite3_mutex_enter().
>>> The comment above the function says:
>>>
>>> [quote]
>>> /*
>>> ** Obtain the mutex p. If some other thread already has the mutex, block
>>> ** until it can be obtained.
>>> */
>>> [/quote]
>>>
>>> The DLL does not start any threads, in fact the application will be 1
>>> thread only.
>>> So is there some compile-time switch I should use to mitigate the issue?
>>>
>>> Moreover I don't understand why am I getting the assertion - there is no
>>> MT
>>> involved.
>>>
>>> Can someone shed some lights?
>>>
>>> Thank you.
>>> _______________________________________________
>>> sqlite-users mailing list
>>> sqlite-users at mailinglists.sqlite.org
>>> http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
>>>
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