I am using ICU lib for Exemplar, I am getting undefined ref for `ulocdata_open_63'
I am not using "ulocdata_open_63" function but "ulocdata_open". Library is linked properly.
Why it is looking for ulocdata_open_63 definition even though I am not calling it.
Sample code:-
#include <stdio.h>
#define UNICODE
#include <unicode/uloc.h>
#include <unicode/ulocdata.h>
#include <unicode/urename.h>
typedef unsigned short U16;
int main()
{
char localeID[ULOC_FULLNAME_CAPACITY+ULOC_KEYWORD_AND_VALUES_CAPACITY] = "en_US";
UErrorCode icuStatus = U_ZERO_ERROR;
ULocaleData* uld = ulocdata_open("en", &icuStatus);
...
}
It looks you're linking against a ICU library that was built with ICU version suffixes, which is the default. To build a library without version suffixes you'll have to add the flag --disable-renaming to the configure build step of ICU4C.
See https://unicode-org.github.io/icu/userguide/icu4c/build.html#icu-as-a-system-level-library.
Related
I'm building a Gtk application in Vala and would like to use the Gio library and more specifically the g_app_info_get_all() function. I am able to achieve this in C as follows:
#include <gtk/gtk.h>
#include <glib/gi18n.h>
#include <gio/gdesktopappinfo.h>
int main(int argc, char *argv[])
{
...
GDesktopAppInfo *app_info;
GList *app_list, *l;
gtk_init(&argc, &argv);
...
app_list = g_app_info_get_all();
...
}
How do I achieve the same in Vala?
ChatGPT suggested me to use Gio.AppInfo.get_all()
and even though
pkg-config --modversion gio-2.0 returns 2.74.3 but using Gio; throws an error saying the namespace 'Gio' could not be found even when I'm compiling with --pkg gio-2.0 flag.
The namespace is GLib, this is shown as {} Glib in Valadoc. The GLib namespace is used by default, so the following will work:
void main () {
var result = AppInfo.get_all ();
foreach (var app in result) {
print (#"$(app.get_display_name())\n");
}
}
Compile with:
valac example.vala --pkg gio-2.0
I'm trying to populate a query for a C++ using mongocxx driver.
The query in Javascript would be like:
{unit_id: {$in: [ObjectId('58aee90fefb6f7d46d26de72'),
ObjectId('58aee90fefb6f7d46d26de73']
}
}
I was thinking that the following code could work to generate the array part, but it doesn't compile.
#include <cstdint>
#include <iostream>
#include <vector>
#include <bsoncxx/json.hpp>
#include <bsoncxx/types.hpp>
#include <mongocxx/client.hpp>
#include <mongocxx/stdx.hpp>
#include <mongocxx/uri.hpp>
#include <mongocxx/instance.hpp>
using bsoncxx::builder::stream::close_array;
using bsoncxx::builder::stream::close_document;
using bsoncxx::builder::stream::document;
using bsoncxx::builder::stream::finalize;
using bsoncxx::builder::stream::open_array;
using bsoncxx::builder::stream::open_document;
mongocxx::instance instance {};
mongocxx::client client{mongocxx::uri{}};
mongocxx::database db = client["banff_development"];
mongocxx::collection coll = db["units"];
int main()
{
mongocxx::cursor cursor = coll.find
(document{} << "provider_id" << bsoncxx::oid("58aee90fefb6f7d46d26de4a")
<< finalize);
bsoncxx::builder::stream::document unit_filter_builder;
for (auto a: cursor)
{
unit_filter_builder << a["_id"].get_oid();
}
return 0;
}
Where can I find an working example for queries using ObjectId arrays to filter.
To build an array, you need to use the array builder, not the document builder. The declaration of the builder for the array should be bsoncxx::builder::stream::array unit_filter_builder. It also looks like you're missing a couple of includes for the various stream builder types.
As an aside, it's better to shy away from the stream builder, as it's very easy to run into issues when using it. This and this are good examples of the trickiness of using the stream builder properly. Instead of using the stream builder, you can use the basic builder, which has a much simpler implementation and gives you much saner error messages if you make a mistake.
I real need help over here, I have to do this ASCIITwitter project for an university's exam and I'm stucked with this problem:
I have to add a header file and a source file on my project of course, so first I tried some easy code to see if I'm capable to do this.
Just a program to do some square operations:
There's my code:
Twitter.h
#ifndef TWITTER_H_
#define TWITTER_H_
int square(int);
#endif /* TWITTER_H_ */
Twitter.c
#include "Twitter.h"
int square(int x)
{
return x*x;
}
main.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "Twitter.h"
int main(void)
{
int y;
y=square(5);
printf("%d\n",y);
system("PAUSE");
}
But it give to me "undefined reference to 'square' and I really don't know how to fix this. I've tried searching on internet, but I'm working on windows, I don't have any makefile, I just want to make this work. Please help me.
I am trying to properly declare and define global variables in separate files and include them in a third file which deals with class declaration.
The three files are:
1) global.h
#ifndef GLOBAL_H_INCLUDED
#define GLOBAL_H_INCLUDED
extern const int marker_num;
extern const int dim;
using namespace std;
#endif // GLOBAL_H_INCLUDED
2) global.cpp
#include <iostream>
#include <cstdio>
#include <cmath>
#include "global.h"
#include "WorldState.h"
#include "Robot.h"
#include "Sensor.h"
#include "Marker.h"
constexpr const int marker_num = 10;
constexpr const int dim = (2 * marker_num) + 3;
3) WorldState.h
#ifndef WORLDSTATE_H
#define WORLDSTATE_H
#include "global.h"
#include "global.cpp"
class WorldState{
public:
WorldState(float a[], float b[dim][dim]);
get_wstate();
protected:
private:
float w_state[];
float covar_matrix[dim][dim];
};
#endif // WORLDSTATE_H
I am using the global variable dim to declare and define a multidimensional array. I have declared dim inside global.h and defined it inside global.cpp. Now, I have a class called WorldState and inside its header, I am using dim. If I comment out #include "global.cpp", it throws the following error:
C:\Users\syamp\Documents\codeblocks\slam\WorldState.h|10|error: array bound is not an integer constant before ']' token
My understanding is that including the .h file includes the corresponding .cpp as well, and that all declarations should be inside .h and all definitions should be inside .cpp. However, it doesn't seem to work in this case.
1) If I decide to include global.cpp file inside WorldState.h, isn't it bad programming practice? I am trying to write a good code not just a code that works.
2) An alternative is to define values of variable(s) dim (and marker_num) inside global.h. Is that good programming practice?
3) I believe there is something that I am missing. Kindly suggest the best method to resolve this issue. I am using codeblocks and C++11. Thanks in advance.
I am using the global variable dim to declare and define a multidimensional array.
When declaring a fixed-length array at compile-time, the value(s) of its dimension(s) must be known to the compiler, but your separation prevents the value of dim from being known to the compiler at all, so dim cannot be used to specify fixed array dimensions. Any code that uses dim will just compile into a reference to it, and then the linker will resolve the references after compilation is done. Just because dim is declared as const does not make it suitable as a compile-time constant. To do that, you must define its value in its declaration, eg:
#ifndef GLOBAL_H_INCLUDED
#define GLOBAL_H_INCLUDED
static constexpr const int marker_num = 10;
static constexpr const int dim = (2 * marker_num);
using namespace std;
#endif // GLOBAL_H_INCLUDED
Otherwise, if you keep dim's declaration and definition in separate files, you will have to dynamically allocate the array at run-time instead of statically at compile-time.
I have declared dim inside global.h and defined it inside global.cpp.
That is fine for values you don't need to use until run-time. That will not work for values you need to use at compile-time.
My understanding is that including the .h file includes the corresponding .cpp as well
That is not even remotely true. The project/makefile brings in the .cpp file when invoking the compiler. The .h file has nothing to do with that.
that all declarations should be inside .h and all definitions should be inside .cpp.
Typically yes, but not always.
If I decide to include global.cpp file inside WorldState.h, isn't it bad programming practice?
Yes.
An alternative is to define values of variable(s) dim (and marker_num) inside global.h. Is that good programming practice?
Yes, if you want to use them where compile-time constants are expected.
I'm using Eclipse and MinGW. I've got undefined reference to error to all that I write in h files, that I do include in cpp-file where main located. I create an empty project, and the same thing again (
main.cpp
#include <iostream>
#include "Stack.h"
using namespace std;
int main(){
Stack<int> stack(10);
cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!
return 0;
}
stack.h
#ifndef STACK_H_
#define STACK_H_
template <class T>
class Stack{
private:
struct StackEl;
StackEl *top;
public:
Stack();
Stack(T el);
~Stack();
void Push(const T& el);
T Pop();
};
#endif /* STACK_H_ */
and stack.cpp inplements everything from stack.h
If I include not h-file, but cpp - all works. Help please!
I've got following errors
D:/Workspacee/Stack2/Debug/../src/Stack2.cpp:16: undefined reference to `Stack<int>::Stack(int)'
D:/Workspacee/Stack2/Debug/../src/Stack2.cpp:18: undefined reference to `Stack<int>::~Stack()'
D:/Workspacee/Stack2/Debug/../src/Stack2.cpp:18: undefined reference to `Stack<int>::~Stack()'
This is a linker error. I'm no Eclipse expert, but you have to tell it somehow to add Stack.o to the linking command.
If you include Stack.cpp instead of Stack.h, the implementations from the cpp-file get included into main.cpp by the preprocessor before compilation, so the linking stage has no unresolved references to outside functions.
My bad, that is becouse templates! When you use template, all code, including realization of functions, must be in header-file, or you have to write prototypes for every type you are going to use you template-functions with. I've forgot about that working with templates is not the same as with usual function :(