Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
Thank you guys for the responses. Great info to consider. I was quite confused but the fact that by waiting some length of time after startup of the app, that everything appeared to work. I repeated ran the troublesome call (without stopping the app), and it would work the 6-7 times of making the call. Bob Moran On Fri, Sep 5, 2014 at 10:15 AM, Nelson, Erik - 2 < erik.l.nel...@bankofamerica.com> wrote: > Bob Moran wrote on: Friday, September 05, 2014 12:07 AM > > On Wed, Sep 3, 2014 at 1:29 PM, Nelson, Erik - 2 < > > erik.l.nel...@bankofamerica.com> wrote: > > > > > Bob Moran wrote on Wednesday, September 03, 2014 12:45 PM > > > > > > > > One added note: My GUI is using QT4, where in this case the SQL > > text > > > > goes something like: > > > > > > > > QString qstr = "select id, step, temp from protocols where id > > > > = %1"; > > > > qstr = qstr.arg(id); > > > > char * str = (char*)qPrintable(qstr); > > > > sqlite3_prepare_v2( db, str, qstr.Length+1, , NULL) > > > > > > > > > > That's pretty different than the pseudocode you presented earlier. > > > > > > From the docs for qPrintable > > > http://qt-project.org/doc/qt-4.8/qtglobal.html#qPrintable > > > > > > ** > > > Returns str as a const char *. This is equivalent to > > > str.toLocal8Bit().constData(). > > > > > > The char pointer will be invalid after the statement in which > > > qPrintable() is used. This is because the array returned by > > > toLocal8Bit() will fall out of scope. > > > > > > > > > Your str is likely pointing to memory that has been freed? > > > > > Are you implying that I must copy the text returned by qPrintable(sql) > > to a safe location before calling a method that uses it? I thought that > > the string would be valid until I return from the routine. > > Based on my reading of the documentation, yes. > > The char pointer will be invalid after the *statement* in which > qPrintable() is used. > > You've already provided additional evidence that your string is pointing > to unallocated memory... you previously wrote > > >Bob Moran wrote on 03. September 2014 06:25 > >>I discovered that a malloc call for 500+ bytes was returning a pointer 8 > bytes below my SQL string > > On the face of it, I'd suggest that indicates that the memory pointed by > your char* has been reallocated since it was returned to the free store. > > Also, as Alessandro mentioned, the length you're using is likely > unreliable. > > Erik > > -- > This message, and any attachments, is for the intended recipient(s) only, > may contain information that is privileged, confidential and/or proprietary > and subject to important terms and conditions available at > http://www.bankofamerica.com/emaildisclaimer. If you are not the > intended recipient, please delete this message. > ___ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
Erik, Are you implying that I must copy the text returned by qPrintable(sql) to a safe location before calling a method that uses it? I thought that the string would be valid until I return from the routine. Bob Moran On Wed, Sep 3, 2014 at 1:29 PM, Nelson, Erik - 2 < erik.l.nel...@bankofamerica.com> wrote: > Bob Moran wrote on Wednesday, September 03, 2014 12:45 PM > > > > One added note: My GUI is using QT4, where in this case the SQL text > > goes something like: > > > > QString qstr = "select id, step, temp from protocols where id > > = %1"; > > qstr = qstr.arg(id); > > char * str = (char*)qPrintable(qstr); > > sqlite3_prepare_v2( db, str, qstr.Length+1, , NULL) > > > > That's pretty different than the pseudocode you presented earlier. > > From the docs for qPrintable > http://qt-project.org/doc/qt-4.8/qtglobal.html#qPrintable > > ** > Returns str as a const char *. This is equivalent to > str.toLocal8Bit().constData(). > > The char pointer will be invalid after the statement in which qPrintable() > is used. This is because the array returned by toLocal8Bit() will fall out > of scope. > > > Your str is likely pointing to memory that has been freed? > > Erik > > -- > This message, and any attachments, is for the intended recipient(s) only, > may contain information that is privileged, confidential and/or proprietary > and subject to important terms and conditions available at > http://www.bankofamerica.com/emaildisclaimer. If you are not the > intended recipient, please delete this message. > ___ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
Thank you for the prompt responses. Bob Moran -Original Message- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of Simon Slavin Sent: Wednesday, September 03, 2014 12:41 PM To: General Discussion of SQLite Database Subject: Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup On 3 Sep 2014, at 5:18pm, Bob Moran <bmo...@cicaccess.com> wrote: > I am using the amalgamation. Simply added the SQLITE3.c and .H files to my > project. I am developing with VisualGDB (VS 2010) cross compiling (building > on Windows 7, running on RPI). No added compiler directives (hopefully, that > is the problem). I'm sorry. You gave clear answers to my questions but unfortunately they do not indicate any problem with your setup. I hope someone know knows the internals of SQLite better than me can help you investigate this. Simon. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
One added note: My GUI is using QT4, where in this case the SQL text goes something like: QString qstr = "select id, step, temp from protocols where id = %1"; qstr = qstr.arg(id); char * str = (char*)qPrintable(qstr); sqlite3_prepare_v2( db, str, qstr.Length+1, , NULL) -Original Message- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of Simon Slavin Sent: Wednesday, September 03, 2014 12:51 AM To: General Discussion of SQLite Database Subject: Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup > On 3 Sep 2014, at 5:24am, Bob Moran <bmo...@cicaccess.com> wrote: > > Found more of what the issue is. I noticed that my SQL text was being > overwritten on the return from the call to prepare_v2. > Stepping through the SQlite3 code I discovered that a malloc call for 500+ > bytes was returning a pointer 8 bytes below my SQL string. > Don't have the foggiest notion as to why. My string is on the heap. If I wait > some time before making the call (my program is just waiting for input, then > the malloc call returns a pointer far removed from my passed in SQL text. > Must be some kind on Linux issue? Are you using a SQLite library or including the amalgamation source code ? If you're using the SQLite source are you using any SQLite compiler defs ? Which compiler are you using ? Simon. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
I am using the amalgamation. Simply added the SQLITE3.c and .H files to my project. I am developing with VisualGDB (VS 2010) cross compiling (building on Windows 7, running on RPI). No added compiler directives (hopefully, that is the problem). Bob Moran -Original Message- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of Simon Slavin Sent: Wednesday, September 03, 2014 12:51 AM To: General Discussion of SQLite Database Subject: Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup > On 3 Sep 2014, at 5:24am, Bob Moran <bmo...@cicaccess.com> wrote: > > Found more of what the issue is. I noticed that my SQL text was being > overwritten on the return from the call to prepare_v2. > Stepping through the SQlite3 code I discovered that a malloc call for 500+ > bytes was returning a pointer 8 bytes below my SQL string. > Don't have the foggiest notion as to why. My string is on the heap. If I wait > some time before making the call (my program is just waiting for input, then > the malloc call returns a pointer far removed from my passed in SQL text. > Must be some kind on Linux issue? Are you using a SQLite library or including the amalgamation source code ? If you're using the SQLite source are you using any SQLite compiler defs ? Which compiler are you using ? Simon. ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
Found more of what the issue is. I noticed that my SQL text was being overwritten on the return from the call to prepare_v2. Stepping through the SQlite3 code I discovered that a malloc call for 500+ bytes was returning a pointer 8 bytes below my SQL string. Don't have the foggiest notion as to why. My string is on the heap. If I wait some time before making the call (my program is just waiting for input, then the malloc call returns a pointer far removed from my passed in SQL text. Must be some kind on Linux issue? Bob Moran Continental Access / NAPCO Security Technologies 355 Bayview Ave. Amityville, N.Y. 11701 631.842.9400 x327 rmo...@cicaccess.com -Original Message- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of Roger Binns Sent: Tuesday, September 02, 2014 12:45 PM To: General Discussion of SQLite Database Subject: Re: [sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup On 29/08/14 12:55, Bob Moran wrote: > The return code (rc) is SQLITE_OK, but "stmnt" is NULL (0) > > if I start the application and wait for at least 1 minute, everything works. You get NULL back from prepare with SQLITE_OK if the statement doesn't do anything. Examples are empty strings or comments. Chances are that is actually what is happening in your case. Roger ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users ___ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
[sqlite] Cannot retrieve SQLite Db Data Immediately After Application Startup
Application running on Linux Debian (Raspberry Pi. I am using QT4 and
SQLite3.c V3.8.6 embedded in the application).using VisualGDB cross
compiler running in RPI. The problem occurs on first startup.
With the database open via:
sqlite3_open_v2("/home/pi/mydatabase.db", , SQLITE_OPEN_READWRITE, NULL
);
sqlite3_stmt *stmt;
const char s = "select rowid, name from protmaster";
int len = strlen (s);
int rc = sqlite3_prepare_v2(db, s, len+1, , NULL);
if (rc == SQLITE_OK && stmt != NULL)
{
...
}
The return code (rc) is SQLITE_OK, but "stmnt" is NULL (0)
if I start the application and wait for at least 1 minute, everything works.
my application is doing nothing at this point, just waiting for input,
which in my cast is clicking on a button. No multi-threading involved. I
attempted a quick step thru of the code, but kinda got lost in the parsing.
No internal errors were being set
Any suggestions would be appreciated.
Bob Moran
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