I know there have been questions asked before about this problem but none seem to shine a light on my problem which is, I am trying to compile a C application and want to access SQLite from within the code (as per test app below) using Eclips as a compile and debugging environment.
I know the .h files are being accessed. the code has as many lines commented out to do with iostream as I have tried to compile this as a C++ app as well.
I get errors one for each of 2 the SQL API.
The real question is do I have to set and How do I set a dependency in Eclipse to allow the api to resolve. Thanks
the code
#include <sqlite3.h>
int main()
{
int RetVal;
RetVal = OpenDB();
return RetVal;
}
int OpenDB()
{
sqlite3 *db; // database connection
int rc; // return code
char *errmsg; // pointer to an error string
/*
* open SQLite database file test.db
* use ":memory:" to use an in-memory database
*/
rc = sqlite3_open(":memory:", &db); //fails on this line
if (rc != SQLITE_OK)
{
goto out;
}
/* use the database... */
out:
/*
* close SQLite database
*/
sqlite3_close(db); //fails on this line
return 0;
}
You need to link the sqlite3 library along with your program:
gcc main.c -lsqlite3
Related
I am trying to build an MWE using libical with an example pretty much cut-and-pasted from the libical docs as follows:
#include <stdlib.h>
#include <libical/ical.h>
const char* calendar_file = "orage_export.ics";
//*****************************************************************************
char* read_stream(char* s, size_t size, void* d)
{
return fgets(s, size, (FILE*)d);
} // read_stream()
//*****************************************************************************
int main()
{
char* line;
icalcomponent* component;
icalparser* parser = icalparser_new();
// open file (first command-line argument)
FILE* stream = fopen(calendar_file, "r");
if(stream == NULL)
{
printf("unable to open %s\n", calendar_file);
exit(-1);
}
// Associate the FILE with the parser so that read_stream will have access to it
icalparser_set_gen_data(parser, stream);
do
{
// Read the file, line-by-line, and parse the data
line = icalparser_get_line(parser, read_stream);
component = icalparser_add_line(parser, line);
// If icalparser has finished parsing a component, it will return it
if(component != 0)
{
// Print the parsed component
printf("%s", icalcomponent_as_ical_string(component));
icalparser_clean(parser);
printf("\n---------------\n");
icalcomponent_free(component);
}
}
while(line != 0);
fclose(stream);
return 0;
}
But I am getting link issues that I cannot resolve. Obviously, I am linking against (the latest version of) libical + pthreads. I then got an undefined reference to ucal_getKeywordValuesForLocale_66 which I can resolve by adding libicui18n.a. But then I get undefined reference errors for "vtable for icu_66::UnicodeString", "icu_66::UnicodeString::setTo" and "icu_66::~UnicodeString" so on, which look very much like C++ errors associated with ICU components. But I am building a plain C program?
What is the set of libraries I need to get the MWE above working? And why am I getting what seem to be class-based link errors when building a vanilla C program?
I am on Linux Mint 20.2, and using the repo versions of all libraries other than libical itself.
Peter
EDIT: In fact, answered my own question!
Looking carefully (properly?) at the output, the undefined issues were connected to libicui18n, so not really an iCal problem at all. Doh!
The fix was to notice that the iCal folks had provided a pkg-config script so adding pkg-config --libs --cflags libical to the compiler line worked. (I guess the ICU dependencies are fixed implicitly.)
I'm trying to link sqlite3 library to CMakeList in Clion using the following code:
find_package(SQLite3)
target_link_libraries(IIWProject SQLite::SQLite3)
Library has been loaded but when i Run the code, Clion shows the following error:
SQL logic error
The database has been loaded but when sqlite3_prepare_v2(db, query, -1, &stmt, NULL) was called return SQL logic error
void get_db(sqlite3 **db){
int rc;
if ((rc = sqlite3_open("db_project.db", db)) != SQLITE_OK){
//fprintf(stderr, "Failed to open DB.\n");
fprintf(stderr,"Failed to open DB: %s\n\r", sqlite3_errstr(rc));
exit(EXIT_FAILURE);
}
}
int clear_table(sqlite3 *db){
sqlite3_stmt *stmt;
int rc;
char* query = "DELETE FROM resources";
if ((rc=sqlite3_prepare_v2(db, query, -1, &stmt, NULL)) != SQLITE_OK){
fprintf(stderr,"Failed to prepare statement: %s\n\r", sqlite3_errstr(rc));
return 1;
}
if ((rc = sqlite3_step(stmt)) != SQLITE_DONE){
fprintf(stderr,"Delete failed: %s\n\r", sqlite3_errstr(rc));
return 1;
}
return 0;
}
How can I try to fix it?
EDIT:
If I compile, without Clion manually, with gcc -lsqlite3,it work
Now that we've established that the table doesn't exist when you run your program though your IDE...
The current working directory when you run your program through a command line is different than the current working directory your IDE runs it in. Since you're using a relative path to the database file, this means you're using a different one depending on how you run your program. Only one of the databases actually has the table(s) you're trying to use.
Some solutions:
Use an absolute path to the database.
Configure your IDE to use the same working directory as when you're running your program through a command line.
I have have a working project like with the following code , running on Visual Studio 2013, windows 7 N.
I tried to replace luaL_loadfile() with luaL_loadbuffer(L,s,strlen(s),name), so that I could put the script as a string together in the main instead, because in my other project with IAR, I have problem with opening file in the project, but I managed to call a lua script directly with putting the script as a string in the main(). My question would be: how does this luaL_loadbuffer() work? I mean, if I understand this function correctly, luaL_loadbuffer(L,s,strlen(s),name), the "s" means a string. I tried to debug with luaL_loadbuffer(), but could not passing the debug, always got error status= 2. Besides I also see somebody else used luaL_loadbuffer() to load the script file, so I am confused now. Can anyone help me?
-- last.lua
function f ()
print("Hello from Lua")
end
#include <lua.h>
#include <lauxlib.h>
#include <stdlib.h>
#include <stdio.h>
int main()
{
double z;
int error;
lua_State *L = luaL_newstate();
luaL_openlibs(L);
if (luaL_loadfile(L, "last.lua") || lua_pcall(L, 0, 0, 0))
{
printf("error: %s", lua_tostring(L, -1));
return -1;
}
lua_getglobal(L, "f");
if (!lua_isfunction(L, -1))
{
lua_pop(L, 1);
return -1;
}
if (lua_pcall(L, 0, 0, 0) != 0)
{
printf("error running function `f': %s\n", lua_tostring(L, -1));
return -1;
}
lua_close(L);
return 0;
}
Yes, you should be able to do this, assuming you load the file as one chunk (and not try to process it by line or by some other chunk as this will probably make those parts invalid Lua code). There is an example in "Programming Lua" that shows how loadbuffer can be used.
Two additional suggestions: (1) don't remove new lines from the file you read and pass it exactly as is to loadbuffer (otherwise --comment\ncode will turn code into comment), (2) make name look like #name as it will make name to be recognized as the file name (for example, in errors thrown from that code). See description under "source" in 4.9.
I'm using SQLite 3 in a C application of mine. It has worked like a charm up until now, when I've started to write unit tests. The function in question is a pretty small. It opens an in-memory database, prepares a statement and then does some stuff with it. Problem is that the app crashes with a segmentation fault at the sqlite3_prepare_v2 function call. I've tried to debug it and check to see that all arguments are valid, which they seem to be.
Below, I've pasted a minimal example which causes segfault in the same way. The backtrace lists sqlite3LockAndPrepare as the function where it crashes (called by sqlite3_prepare_v2).
As I mentioned above, I use SQLite without any problems in the rest of my app. I just can't figure out what the difference in usage is, since it's split up in several different routines which also does other stuff. The one thing I can spot is the use of an in-memory database instead of on-disk, but I tried with it on disk, and it made no difference.
#include <stdlib.h>
#include <stdio.h>
#include <sqlite3.h>
int main(void)
{
sqlite3 *db;
sqlite3_stmt **stmt;
const char *str = "CREATE TABLE Test (t1 varchar(8) NOT NULL);";
if (SQLITE_OK != sqlite3_open(":memory:", &db)) {
printf("Can't open...\n");
return 1;
}
sqlite3_prepare_v2(db, str, -1, stmt, NULL);
return 0;
}
The fourth argument to sqlite3_prepare_v2() is supposed to be a valid pointer to an sqlite3_stmt *. You are instead passing an undefined value (since your variable stmt is never initialized). (Note, too, that even if that did not crash the program, you could not receive a pointer to the prepared statement that way.)
You should do this, instead:
int main(void)
{
sqlite3 *db;
sqlite3_stmt *stmt;
const char *str = "CREATE TABLE Test (t1 varchar(8) NOT NULL);";
/* ... create database ... */
sqlite3_prepare_v2(db, str, -1, &stmt, NULL);
return 0;
}
I'm having memory management related crashes when using SQLite. It only crashes once every 30 or so tries unless I enable Guard Malloc (a test mode) in Xcode, in which case it crashes the second time I prepare a statement, 100% of the time. I think it has to do with how I'm opening or using the database, but I can't find anything wrong, BUT I'm a newbie with SQLite. Is there anything I'm forgetting?
Wrapper function for opening:
int databaseConnect(sqlite3 **db){
int rc = sqlite3_open_v2(dbURL, db, SQLITE_OPEN_READWRITE, NULL);
if(rc!=SQLITE_OK){
fprintf(stderr, "Can't open database! Error: %s\n", sqlite3_errmsg(*db));
sqlite3_close_v2(*db);
return(SQL_ERROR);
}
return NO_ERROR;
}
Wrapper function for sending commands:
int databaseCommand(char* command, sqlite3* db){
char* error = NULL;
int ret = sqlite3_exec(db, command, NULL, 0, &error);
if (ret!=SQLITE_OK){
printf("SQL command aborted. Error: %s\n", error);
return SQL_ERROR; //EDIT: this will cause the database to close later
}
if (error) sqlite3_free(error);
return NO_ERROR;
}
How I use my opening function:
//ONCE IN MAIN THREAD, BEFORE ANY OTHER THREADS:
sqlite3* db = NULL;
databaseConnect(&db);
//call databaseCommmand a few times while creating tables...
sqlite3_close_v2(db);
//ONCE PER THREAD IN OTHER THREADS:
sqlite3* db = NULL; databaseConnect(&db);
How I use sqlite3_prepare_v2 in my non-main threads (and where it crashes):
struct LinkedList* databaseSelect(char* command, sqlite3* db){
sqlite3_stmt* stmt = NULL;
int retval = retval = sqlite3_prepare_v2(db,command,(strlen(command))*sizeof(char),&stmt,NULL); //crashes here the second time I run it
if(retval!=SQLITE_OK){
printf("Selecting data from database failed! Error: %s\n", sqlite3_errmsg(db));
sqlite3_free(stmt);
return NULL; //EDIT: this will cause the database to close later
}
// Then the function does stuff involving sqlite3_column_text and sqlite3_column_int…
sqlite3_free(stmt);
// return the linked list result
}
The error I get and the part of the SQLite3 library that causes it:
EXC_BAD_ACCESS (code=1) in this part of sqlite3.c:
/*
** Create a new virtual database engine.
*/
SQLITE_PRIVATE Vdbe *sqlite3VdbeCreate(sqlite3 *db){
Vdbe *p;
p = sqlite3DbMallocZero(db, sizeof(Vdbe) );
if( p==0 ) return 0;
p->db = db;
if( db->pVdbe ){
db->pVdbe->pPrev = p; //error is right here; db->pVdbe is pointing to invalid address
}
p->pNext = db->pVdbe;
p->pPrev = 0;
db->pVdbe = p;
p->magic = VDBE_MAGIC_INIT;
return p;
}
Whenever I use sqlite3_column_text, I copy the result immediately. I do not modify the result. In databaseCommand and databaseSelect, char* command is null-terminated and valid (I checked). Each thread uses its own database handle, each connected to the same database. However, in this test case, there is only one thread connected to the database at any given time.
If there really is nothing wrong here, I have to assume that I trampled the memory elsewhere in my program, and I can't find anything in the rest of the program that even looks a bit dangerous. Plus it's suspicious that SQLite is the one thing crashing every time.
The sqlite3_prepare_v2 documentation says:
The calling procedure is responsible for deleting the compiled SQL statement using sqlite3_finalize() after it has finished with it.
sqlite3_free() can be used only for raw memory allocated with sqlite3_alloc(), or when a function such as sqlite3_exec() is documented as requiring it.
Since you are using multiple threads operating on same database just make sure you close and reopen the database from these thread after every operation. You should also try not to neglect the error condition and add the close statement there also as shown below.
if(retval!=SQLITE_OK){
printf("Selecting data from database failed! Error: %s\n", sqlite3_errmsg(db));
sqlite3_free(stmt);
sqlite3_close(your_db_ptr);
......
}
sqlite3_prepare_v2() alone just compiles the SQL but does not run it. Call sqlite3_step() on the compiled statement to run it, or use sqlite3_exec() that combines prepare+step+finalize into one function call. From here.
Hope this helps.