I am new c++ so forgive me to be asking this question. I created a project and run it the first time, it is successful. But when i start another project and i added 4 classes to it (you can see from the tabs) and the main.cpp is unable to run. I am confused as the codes are exactly the same in both projects.
Run Successful:
Success
Build Successful but run failed:
Run Failed
What are the solutions to solve this problem?
Do i have to post codes of all my classes? (there are 8 files)
student.h:
#ifndef CLSSTUDENT_H
#define CLSSTUDENT_H
#include <string>
#include <iostream>
using namespace std;
class clsStudent {
protected:
string name;
string student_no;
string program;
public:
clsStudent(string n, string sn,string prog );
virtual void displayStudentDetails();
};
student.cpp
#include "TutorialClass.h"
void TutorialClass::addStudent(clsStudent std)
{
_students.push_back(std);
}
int TutorialClass::getStudentCount()
{
return _students.size();
}
void TutorialClass::display()
{
}
#endif /* CLSSTUDENT_H */
I open up a new project and added only this class. It is unable to run as well. What is the problem in the codes?
It seems that your program only fails to run when it's compiled with other files. My bet is that in these files you've got buggy code that is running before main() gets to run.
This can happen in cases like this:
int f() {
throw; // bam! Uncaught exception;
}
int x = f(); // this runs before main()
Or this:
class C {
C() {
cout << "This runs before main() too!" << endl;
}
};
C my_c; // calls constructor
In both cases: code was executed before main(). You want this because you want your global variables to be initialized before running main(). If this initialization code manages to crash the program via a segfault or an exit() call or throwing some exception which isn't caught? You've got a crashed program before it ever even gets the chance to run.
Related
Although I read a few google-results for that error I can't find my problem for this error, not even while trying to reduce everything to its very basic content.
That's my testclass.h:
class TESTCLASS {
public:
TESTCLASS();
};
int x; // I added this for testing if the file is included from my main code file
x=10; // It is and throws this error: testclass.h:8:1: error: 'x' does not name a type, which I don't understand neither, but it't not the main problem here
testclass.cpp:
#include "testclass.h"
TESTCLASS::TESTCLASS() {
// do some stuff
}
and here's my main code file:
#include "lib/testclass.h"
TESTCLASS test;
void setup() {
// put your setup code here, to run once:
}
void loop() {
// put your main code here, to run repeatedly:
}
This throws the error
/var/folders/b5/qc8dstcn02v_hyvgxsq4w9vr0000gq/T//ccQOziAu.ltrans0.ltrans.o: In function `_GLOBAL__sub_I_test':
/Volumes/Daten/stefanherzog/Documents/Nextcloud/Programmierung/Arduino/200515_growboxLibrary_test/200515_growboxLibrary_test.ino:3: undefined reference to `TESTCLASS::TESTCLASS()'
collect2: error: ld returned 1 exit status
exit status 1
So even this is very basic I can't see the problem! I'm using an avr-g++ compiler within my Arduino IDE (v1.8.12).
Can someone please explain me what I'm doing wrong?
it looks like you don't send testclass.cpp to your compiler. If so, your problem does'nt come from your code but your compiling command line.
Using gcc you should have something like :
g++ main.cpp lib/testclass.cpp -o testclass
I don't know the compilation process for arduino but i hope it will helps you finding the solution.
Easiest put testclass.cpp into the same folder as your .ino file. It should show up as a separate tab.
Put testclass.h there as well. and remove the lib subfolder.
And remove the int x=10; definition from the .h file. If both units are including testclass.h, that should end up in a duplicate error.
BTW: an assignment x=10; outside a function is nonsense anyway.
When using subdirectories with the Arduino IDE the subdirectory needs to be named as utility. That's actually it!
Having this structure for example (in ../Arduino/libraries/):
./testclass
./testclass/testclass.h
./testclass/testclass.cpp
./testclass/sub
./testclass/sub/sub.h
./testclass/sub/sub.cpp
testclass.h:
#ifndef __TESTCLASS_H__
#define __TESTCLASS_H__
#include "utility/sub.h"
class TESTCLASS {
public:
TESTCLASS();
};
#endif
testclass.cpp:
#include "testclass.h"
TESTCLASS::TESTCLASS() {
// do some stuff
}
sub.h:
class SUBCLASS {
public:
SUBCLASS();
};
sub.cpp:
#include "sub.h"
SUBCLASS::SUBCLASS() {
// do some stuff
}
You can simply include the "main" testclass.h in your project and instantiate the class and even the subclass:
#include <testclass.h>
TESTCLASS test;
SUBCLASS sub;
void setup() {
// put your setup code here, to run once:
}
void loop() {
// put your main code here, to run repeatedly:
}
I am a little bit new to cpp. And all the concepts of 'includes' tho are important are pretty new and vague forme. I have a few questions which are related to my main question . The main question is:. I have a program which is a file containing 'main' and other 5 classes let's call it 'PROG'. I put them all in one file using no h files at all. The program is running and all is good. The point is, I now have 'test file ' which should test my program. Test file is separated to h file and cpp file. Is there any way to run everything without changing my program 'PROG'?? I don't want to create h files to my 'PROG' . The problem is, the test file uses a few of the claseess written the program 'PROG'. I thought about writing 'includes' cpp in the test file and putting 'pragma once'. I don't know why it doesn't work. Doesn't pragma once work for ' cpp includes'??
Or basically can anyone answer the general question. Which is in short:. You have a file containing main and classes (which all in cpp file with no h file) . And you want to run it with another file (cpp+ h) but both files use each othrr. Which makes a circular use. Is there a way to run it ?
You might be able to write tests, however they will be run at an unspecified time either before or after your program runs, so won't be able to access std::cout etc. If your program uses any static objects, you won't be able to do this.
It will be much easier to move your main into a main.cpp that #includes definitions of your classes, and compile a separate test_main.cpp that instead runs your tests.
As a sketch of the former
class TestFailure{};
class RunAtStartup
{
template<typename Func>
RunAtStartup(Func f) { f(); }
}
extern double function_to_test(int arg);
static RunAtStartup run_function_to_test([]{
// arrange
int param = 0;
// act
double res = function_to_test(param);
// assert
if(res != 1.0) throw TestFailure();
});
Does this help?
PROG:
class C {
void f();
}
#ifndef TEST
void C::f() {
// implementation
}
#endif // TEST
TEST:
#define TEST
#include "main.cpp"
// Your test code here can have instances to class C
C c;
c.f();
But take cpp/h approach as anyone recommends, which is everywhere.
I'd highly recommend using headers, but if you really don't want to modify your original file, you can #include "main.cpp" from your test file and redefine the main symbol during the inclusion. This allows you to create your own main method for the test program.
In test.cpp:
#define main real_main
#include "mymain.cpp"
#undef main
int main(int argc, const char** argv) {
std::cout << "wah" << std::endl;
int fakeargc = 1;
const char* fakeargv[fakeargc] = { "hoo" };
real_main(fakeargc, fakeargv);
}
In main.cpp:
#include <iostream>
int main(int argc, const char** argv) {
std::cout << "hello world " << argv[0] << std::endl;
return 0;
}
So i just learned how to seperate classes and the youtube totourial is stressing on doing this alot, here's the link
https://www.youtube.com/watch?v=NTip15BHVZc&list=PLAE85DE8440AA6B83&index=15
My code is the exact same as his, and in the cpp file theres this thing:
mainClass::myfunction; (mainclass is the name of my class, myfunction is my function)
when i try to execute my program, it gives an error:
unidentified reference to 'mainClass::myfunction()'
here's my main.cpp file code:
#include <iostream>
#include "mainclass.h"
using namespace std;
int main()
{
mainClass bo;
bo.myfunction();
return 0;
}
here's my mainclass.h code:
#ifndef MAINCLASS_H
#define MAINCLASS_H
class mainClass
{
public:
myfunction();
};
#endif // MAINCLASS_H
my mainclass.cpp:
#include "mainclass.h"
#include <iostream>
using namespace std;
mainClass::myfunction()
{
cout << "I am a banana" << endl;
}
I don't know much about these so could you just tell me what the errors here are, because i copied everything correctly from the guy's totourial but still it doesn't work
P.S: this happens to me alot, i understand everything, nothing works, i copy everything, nothing works, and then i literally do exactly what the person is doing, still nothing works on all three of PC's, so i dont think the problem is with the devices lol
I doubt you completely copied and pasted that code because I'm fairly sure a teacher shouldn't be teaching having functions without a specified return type, but let's jump into it anyways...
Possibility #1
You meant to create a constructor for the class. In that case, please make sure the constructor function has the same name as the class. Also, you can't call it through .mainClass(), as it is a constructor.
class mainClass
{
public:
mainClass();
};
mainClass::mainClass()
{
cout << "I am a banana" << endl;
}
Possibility #2 You meant to create the class member function myfunction. You really should be specifying what return type your function is of. Some compilers will auto-assume int return type, and so the function you created is int myfunction();, but you really should be specifying it as void myfunction(); since you didn't return anything. Addl. info: Does C++ allow default return types for functions?
Next, change how you are giving the definition, by adding the return type.
void mainClass::myfunction()
{
cout << "I am a banana" << endl;
}
Possibility #3 Those should work, but another issue is that you might not have linked mainclass.cpp, so there is no definition available. In code blocks, right click on the project name and hit Add Files, then add the mainclass.cpp so the linker can define mainClass::myfunction().
To troubleshoot if the mainclass.cpp is being built with the project, try adding
#error I'm included! to the file mainclass.cpp after #include "mainclass.h". If you get an error I'm included!, then it is linked and you can remove the #error.
In this program, I m creating an object and then just destroying the object using destructor..and I'm using a static variable as a counter...the program compiles successfully but I m not getting any output...and when I try to run it on code block I get a message "code blocks stopped working"..I m at windows 10 with gnu GCC compiler.
#include <iostream>
using namespace std;
class ashish
{
int *age;
public:
static int classm;
ashish()
{
*age=10;
classm++;
}
~ashish(){
cout<<"this going to destroy the object";
delete age;}
};
int ashish::classm=0;
int main()
{
ashish *blast;
blast=new ashish();
cout<<ashish::classm<<"chec"<<endl;
delete blast;
return 0;
}
You're not allocating memory for age, like you did with blast (blast = new ashish();)
Let's consider the following three files.
tclass.h:
#include <iostream>
#include <vector>
template<typename rt>
class tclass
{
public:
void wrapper()
{
//Storage is empty
for(auto it:storage)
{
}
try
{
thrower();
}
catch(...)
{
std::cout << "Catch in wrapper\n";
}
}
private:
void thrower(){}
std::vector<int> storage;
};
spec.cpp:
#include "tclass.h"
//The exact type does not matter here, we just need to call the specialized method.
template<>
void tclass<long double>::thrower()
{
//Again, the exception may have any type.
throw (double)2;
}
main.cpp:
#include "tclass.h"
#include <iostream>
int main()
{
tclass<long double> foo;
try
{
foo.wrapper();
}
catch(...)
{
std::cerr << "Catch in main\n";
return 4;
}
return 0;
}
I use Linux x64, gcc 4.7.2, the files are compiled with this command:
g++ --std=c++11 *.cpp
First test: if we run the program above, it says:
terminate called after throwing an instance of 'double'
Aborted
Second test: if we comment for(auto it:storage) in the tclass.h file, the program will catch the exception in main function. WATWhy? Is it a stack corruption caused by an attempt to iterate over the empty vector?
Third test: lets uncomment back the for(auto it:storage) line and move the method specialization from spec.cpp to main.cpp. Then the exception is caught in wrapper. How is it possible and why does possible memory corruption not affect this case?
I also tried to compile it with different optimization levels and with -g, but results were the same.
Then I tried it on Windows 7 x64, VS2012 express, compiling with x64 version of cl.exe with no extra command line arguments. At the first test this program produced no output, so I think it just crashed silently, so the result is similar with Linux version. For the second test it produced no output again, so result is different from Linux. For the third test the result was similar with Linux result.
Are there any errors in this code so they can lead to such behavior? May the results of the first test be caused by possible bug in compilers?
With your code, I have with gcc 4.7.1:
spec.cpp:6: multiple definition of 'tclass<long double>::thrower()'
You may correct your code by declaring the specialization in your .h as:
template<> void tclass<long double>::thrower();