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.
>> _______________________________________________
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>> sqlite-users at mailinglists.sqlite.org
>> http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
>>
>
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