Hi,
In my C++ application I'm writing/reading some blob data to the
database. This is sample of my code (in 99% taken from example i found
in the internet ):
/**
* This function reads one blob value asqued in zSql query into memory
pointed by pzBlob
* and returns size of allocated memory in pnBlob integer. One MUST
remember to deallocate
* memory provided by pzBlob pointer.
* Example: readBlob("SELECT value FROM table WHERE id=5", &test1, &lenTest);
* \param *zSql Query string f.e. "SELECT value FROM table WHERE id=5"
* \param **pzBlob Pointer to memory where data is retuned. This
memory is allocated automatically. One MUST remember to deallocate it.
* \param *pnBlob Size of data returned in pzBlob
* \return False if anything went wrong, else True;
*/
bool SQLite3pp::readBlob(const char *zSql, unsigned char **pzBlob, int *pnBlob){
if(zErrMsg) sqlite3_free(zErrMsg);
sqlite3_stmt *pStmt;
int rc;
/* In case there is no table entry for key zKey or an error occurs,
** set *pzBlob and *pnBlob to 0 now.
*/
*pzBlob = 0;
*pnBlob = 0;
bool retValue = false;
do {
/* Compile the SELECT statement into a virtual machine. */
rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
// Line 164
if( rc!=SQLITE_OK ){
return false;
}
/* Run the virtual machine. We can tell by the SQL statement that
** at most 1 row will be returned. So call sqlite3_step() once
** only. Normally, we would keep calling sqlite3_step until it
** returned something other than SQLITE_ROW.
*/
rc = sqlite3_step(pStmt);
if( rc==SQLITE_Row ){
/* The pointer returned by sqlite3_column_blob() points to memory
** that is owned by the statement handle (pStmt). It is only good
** until the next call to an sqlite3_XXX() function (e.g. the
** sqlite3_finalize() below) that involves the statement handle.
** So we need to make a copy of the blob into memory obtained from
** malloc() to return to the caller.
*/
*pnBlob = sqlite3_column_bytes(pStmt, 0);
*pzBlob = (unsigned char *)malloc(*pnBlob);
memcpy(*pzBlob, sqlite3_column_blob(pStmt, 0), *pnBlob);
retValue=true;
}
/* Finalize the statement (this releases resources allocated by
** sqlite3_prepare() ).
*/
rc = sqlite3_finalize(pStmt);
/* If sqlite3_finalize() returned SQLITE_SCHEMA, then try to execute
** the statement all over again.
*/
} while( rc==SQLITE_SCHEMA );
return retValue;
}
As you can see I use sqlite3_prepare/sqlite3_finalize pairs. My memory
leak checker ( Deleaker : www.deleaker.com ) reports memory leak at
sqlite3_prepare :
msvcrt.dll!malloc
sqlite3.dll!sqlite3_malloc + 120 bytes
sqlite3.dll!sqlite3_realloc + 27 bytes
sqlite3.dll!sqlite3_release_memory + 200 bytes
sqlite3.dll!sqlite3_release_memory + 242 bytes
sqlite3.dll!sqlite3_set_authorizer + 1072 bytes
sqlite3.dll!sqlite3_set_authorizer + 22149 bytes
sqlite3.dll!sqlite3_declare_vtab + 11632 bytes
sqlite3.dll!sqlite3_prepare16_v2 + 18070 bytes
sqlite3.dll!sqlite3_declare_vtab + 27000 bytes
sqlite3.dll!sqlite3_declare_vtab + 31896 bytes
sqlite3.dll!sqlite3_declare_vtab + 36104 bytes
sqlite3.dll!sqlite3_reset_auto_extension + 12492 bytes
sqlite3.dll!sqlite3_reset_auto_extension + 13270 bytes
sqlite3.dll!sqlite3_prepare + 31 bytes
RSR2.exe!SQLite3pp::readBlob Line 164
(c:\furtado\furtado\sqlite\sqlite3pp.cpp)
I am closing database properly.
Am I doing something wrong or is it some kind of bug?
Bartosz Wiklak
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