I have a class that has a #include inside it containing the member function declarations, like this:
class PContextActions_t {
public:
#define PARG blah...
#include "pActionDecls.h"
#undef PARG
#define PARG
#include "pActionDecls.h"
#undef PARG
void OtherFuncs(); /// Another function
};
because they need to be declared twice with different arguments. When I run doxygen on this project I get documentation for OtherFuncs(), but not for any of the functions declared in pActionDecls.
What can I do about this? I've tried:
ENABLE_PREPROCESSING = YES
MACRO_EXPANSION = YES
CLANG_ASSISTED_PARSING = YES
Related
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.
I want to access a variable in multiple .cpp files. I looked into several resources. I could not solve it though. I am using cmake to build all the codes in this project. Following is an example that exactly matches with my problem. Basically, I want val to print 42 in both code1.cpp and code2.cpp. When, I build these three files it complains: undefined reference to 'he::val' collect2: error:ld returned 1 exit status for both the .cpp files.
header1.h
#ifndef HEADER1_H
#define HEADER1_H
#include <iostream>
namespace he {
extern int val;
}
#endif // HEADER1_H
code1.cpp
#include "header1.h"
#include <iostream>
using namespace he;
int func()
{
std::cout << val << std::endl;
}
int main()
{
val=20;
func();
return 0;
}
code2.cpp
#include <iostream>
#include "header1.h"
using namespace he;
int main()
{
std::cout << val << std::endl;
}
extern int val;
Is a variable declaration. You need, somewhere (in one of your cpp files), to define the variable:
int val;
Actually, since you have two main() functions, these are two separate programs. Then your variable definition needs to be in both, like this:
namespace he {
int val;
}
But your extern declaration in the header file makes your variable global, which is usually frowned upon. It all depends, of course on what your purpose is.
Also, since two main() functions mean two separate programs, there is no variable sharing.
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.
How can I include a file or another, based on the value of a defined string?
This doesn't work:
#define VAR VALUE_A
#if VAR == "VALUE_A"
#include "a.h"
#elif VAR == "VALUE_B"
#include "b.h"
#endif
If it's important, I'm not actually defining VAR, I'm passing it down from the command-line via gcc -D NAME=VALUE.
The == operator does not compare strings. But you have a couple of other options to configure your includes. In addition to the solutions already mentioned in other answers, I like this one because I think it is quite self-explanatory.
/* Constant identifying the "alpha" library. */
#define LIBRARY_ALPHA 1
/* Constant identifying the "beta" library. */
#define LIBRARY_BETA 2
/* Provide a default library if the user does not select one. */
#ifndef LIBRARY_TO_USE
#define LIBRARY_TO_USE LIBRARY_ALPHA
#endif
/* Include the selected library while handling errors properly. */
#if LIBRARY_TO_USE == LIBRARY_ALPHA
#include <alpha.h>
#elif LIBRARY_TO_USE == LIBRARY_BETA
#define BETA_USE_OPEN_MP 0 /* You can do more stuff than simply include a header if needed. */
#include <beta.h>
#else
#error "Invalid choice for LIBRARY_TO_USE (select LIBRARY_ALPHA or LIBRARY_BETA)"
#endif
Your users can now compile with:
$ cc -DLIBRARY_TO_USE=LIBRARY_BETA whatever.c
You can use #ifdef or #ifndef for conditional includes.
#ifdef VALUE_A
#include "a.h"
#endif
#ifdef VALUE_B
#include "b.h"
#endif
The closest possilibility I can think of is to utilize third form of #include directive (C11 §6.10.2/4), namely define VAR with value, that holds actual header filename:
#define VAR "a.h"
then just use the following:
#include VAR