Here is my C++ code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main () {
std::ifstream ifs ("strength_classes.txt", std::ifstream::in);
char c = ifs.get();
while (ifs.good()) {
std::cout << c;
c = ifs.get();
}
ifs.close();
return 0;
}
I then compile it in the tutorial by running the following, but it outputs the error:
Laptop:Downloads Stu$ c++ -c test.cpp
Laptop:Downloads Stu$ g++ -o test.o
clang: error: no input files
I guess you are trying to do the following:
$ g++ test.cpp -c -o test.o
$ g++ test.o -o program
To run your program type
$ ./program
afterwards.
g++ -o test.o
This is wrong. The -o flag is supposed to indicate the filename of the resulting executable, which you're accidentally stating as test.o and then failing to provide inputs.
Write:
g++ -o myBinary test.o
then execute:
./myBinary
Related
I created my Makefile for a simple program but it returns undefined reference for class functions constantly:
g++ -c src/main.cpp -o lib/main.o
g++ -c src/functions.cpp -o lib/functions.o
g++ -c src/Circular.cpp -o lib/Circular.o
g++ lib/main.o -o bin/app.exe
c:/mingw/bin/../lib/gcc/mingw32/9.2.0/../../../../mingw32/bin/ld.exe: lib/main.o:main.cpp:(.text+0x20): undefined reference to `Circular::Circular()'
collect2.exe: error: ld returned 1 exit status
make.exe: *** [app.exe] Error 1
Here is my Makefile:
app.exe: lib/main.o lib/Circular.o lib/functions.o
g++ lib/main.o -o bin/app.exe
lib/functions.o: src/functions.cpp
g++ -c src/functions.cpp -o lib/functions.o
lib/Circular.o: src/Circular.cpp
g++ -c src/Circular.cpp -o lib/Circular.o
lib/main.o: src/main.cpp
g++ -c src/main.cpp -o lib/main.o
Here is a short snippet of main.cpp:
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <fstream>
#include <string>
#include "../include/Circular.h"
#include "../include/functions.h"
using namespace std;
int main(int argc, const char * argv[]) {
Circular item;
return 0;
}
Circular.h:
#include "node.h"
class Circular
{
public:
Circular();
node *start;
node *last;
int counter;
}
Circular.cpp:
#include "../include/Circular.h"
#include <iostream>
using namespace std;
Circular::Circular()
{
start = NULL;
last = NULL;
}
and node.h:
struct node
{
int data;
struct node *next;
struct node *prev;
};
I know the problem is about linker and with Makefile but even though I tried different possible solutions, somehow it doesn't work. Therefore, maybe someone can see the mistake I am making. Thanks!
I managed to create a Makefile from this source .
The Makefile looks like this:
CXX = g++
CXXFLAGS = -std=c++17 -Wall
LXXFLAGS = -std=c++17
OBJECTS = main.o Circular.o functions.o
TARGET = main
$(TARGET): $(OBJECTS)
$(CXX) $(LXXFLAG) $(OBJECTS) -o $(TARGET)
main.o: main.cpp Circular.cpp Circular.h functions.cpp functions.h
$(CXX) $(CXXFLAGS) -c main.cpp
Circular.o: Circular.cpp
$(CXX) $(CXXFLAGS) -c Circular.cpp
functions.o: functions.cpp
$(CXX) $(CXXFLAGS) -c functions.cpp
clean:
rm -f $(TARGET) $(OBJECTS)
And also added cout to you Circular constructor to check the execution as below:
#include "Circular.h"
#include <iostream>
using namespace std;
Circular::Circular()
{
start = NULL;
last = NULL;
cout << "Yes!" << endl;
}
Here's the result:
Output
Don't forget to put a semicolon for your Circular class in your Circular.h.
NOTE: If you aren't able to use make in cmd,use choco install make.
The Makefile should be structured to build the dependencies, then the final assembly into a .exe. Each path should be specified exactly as it is, not approximated:
app.exe: lib/main.o lib/Circular.o lib/functions.o
g++ lib/main.o lib/Circular.o lib/functions.o -o app.exe
lib/main.o: src/main.cpp
g++ -c src/main.cpp -o lib/main.o
lib/functions.o: src/functions.cpp
g++ -c src/functions.cpp -o lib/functions.o
lib/Circular.o: src/Circular.cpp
g++ -c src/Circular.cpp -o lib/Circular.o
The key here is be consistent and that includes things like the order of things specified in this file. Whatever order you pick, stick to it. This makes tracking down problems way easier.
If this project gets more complex you probably want to pivot to using a dependency tracking Makefile template instead of this homebrew one. Note how in those you don't need to specify a rule for each file, but instead a rule for each type of file, as in .cpp -> .o, and the rest happens automatically.
I am having problems understanding the segmentation fault I receive when trying to run icpc-compiled programs.
A simple example consists of the following files:
// Filename: include/lib1.h
#include <string>
namespace Lib1 {
// Template initialization, T: int, double
template< typename T>
T function1( T x, T y );
// Give me the version
std::string VERSION(void);
}
// Filename: include/lib2.h
#include <string>
namespace Lib2 {
// Give me the version
std::string VERSION(void);
}
// Filename: src/main.cpp
#include <iostream>
#include <string>
#include "lib1.h"
#include "lib2.h"
int main( int argc, char* argv[] ) {
std::cout << "Lib1::VERSION() :" << Lib1::VERSION()
<< std::endl;
std::cout << "Lib2::VERSION() :" << Lib2::VERSION()
<< std::endl;
double x = 1., y = 2.;
std::cout << "Lib1::function1(x, y): "
<< Lib1::function1(x, y)
<< std::endl;
return 0;
}
// Filename: src/lib1/lib1.cpp
#include <string>
#include "lib1.h"
template< typename T >
T Lib1::function1( T x, T y ) {
return x * y;
}
std::string Lib1::VERSION(void) {
return std::string("v0.0.2");
}
// Instantiation for dynamic library
template double Lib1::function1(double, double);
template int Lib1::function1(int, int);
// Filename: src/lib2/lib2.cpp
#include <string>
#include "lib2.h"
std::string Lib2::VERSION(void) {
return std::string("v0.0.1");
}
In this simple, stupid example, when I compile the files using
clang++ -Wall -c -fPIC -I include -o liblib1.o src/lib1/lib1.cpp
clang++ -Wall -shared -o liblib1.so liblib1.o
clang++ -Wall -c -fPIC -I include -o liblib2.o src/lib2/lib2.cpp
clang++ -Wall -shared -o liblib2.so liblib2.o
clang++ -Wall -o main.out -I include -L ./ -llib1 -llib2 src/main.cpp
the program runs fine (provided that I modify my LD_LIBRARY_PATH environment variable properly. However, when I use
icpc -Wall -c -fPIC -I include -o liblib1.o src/lib1/lib1.cpp
icpc -Wall -shared -o liblib1.so liblib1.o
icpc -Wall -c -fPIC -I include -o liblib2.o src/lib2/lib2.cpp
icpc -Wall -shared -o liblib2.so liblib2.o
icpc -Wall -o main.out -I include -L ./ -llib1 -llib2 src/main.cpp
then the program gives me:
[1] 27397 segmentation fault (core dumped) LD_LIBRARY_PATH=./:$LD_LIBRARY_PATH ./main.out
I would appreciate if you helped me understand and solve this problem. When I did some research on the web, I came across some sources talking about memory access problems and such, but I am not doing anything fancy right now. Moreover, I tried using ddd (I am not fluent/good in gdb) and running the program there, but the program exists with the segfault immidiately after the program start. I cannot even trace the program (yes, prior to running ddd, I used -debug -g switches).
It happened to be the case that Intel Parallel Studio v16.0.3 has (known) issues for Ubuntu and Arch Linux platforms, and unfortunately these systems are not officially supported, either.
One fast workaround seems to be to downgrade to v16.0.2 for now.
I need to access a C++ function from C but I get some error like :-
/tmp/ccUqcSZT.o: In function `main':
main.c:(.text+0x5): undefined reference to `load_alert_to_db'
collect2: error: ld returned 1 exit status
My main.c code is:-
#include <stdio.h>
extern void load_alert_to_db(void);
int main(void){
/* Create empty queue */
load_alert_to_db();
return 0;
}
C++ code implementation db_manager.cpp is:-
#include <sstream>
#include <iostream>
#include <sstream>
#include <string>
#include <ctime>
#include <cstdlib>
#include <algorithm>
#include <time.h>
#include <cstring>
#include <fstream>
//using namespace oracle::occi;
#include <iostream>
using namespace std;
extern "C" void load_alert_to_db(void)
{
cout<<"db occi"<<endl;
}
makefile is:-
CC= g++
all:
$(CC) -c -Wall -Werror -fPIC db_manager.cpp
$(CC) -shared -o libdb_manager.so db_manager.o
gcc -L/home/oracle/Desktop/storage/ -Wall main.c -o data -ldb_manager
gcc -o data main.c
clean:
rm -f *.o data
so please help me which one is my problem. I am also include
export LD_LIBRARY_PATH=/home/oracle/Desktop/storage/:$LD_LIBRARY_PATH
environmental variable in .bash_profile
gcc -o data main.c
Not sure why you have this line in your makefile since it will compile main.c without reference to the previously created library and hence cause an undefined-symbol error such as the one you're seeing.
This is especially so, since you appear to have done it the right way on the preceding line:
gcc -L/home/oracle/Desktop/storage/ -Wall main.c -o data -ldb_manager
However, the entire point of using makefiles is so that it figures out the minimum necessary commands for you, based on dependencies. Lumping a large swathe of commands into a single rule tends to defeat that purpose. You would be better off making your rules a little more targeted, such as (untested but should be close):
all: data
data: main.o libdb_manager.so
gcc -o data main.o -ldb_manager
main.o: main.c
gcc -o main.o main.c
libdb_manager.so: db_manager.cpp
g++ -c -Wall -Werror -fPIC -o db_manager.o db_manager.cpp
g++ -shared -o libdb_manager.so db_manager.o
That way, if you make a small change to one part (like main.c), it doesn't have to go and compile/link everything in your build tree.
Your makefile seems to be completely broken and random, and you're not even linking the required object files. You can simplify this:
all:
$(CC) -c -Wall -Werror -fPIC db_manager.cpp
$(CC) -shared -o libdb_manager.so db_manager.o
gcc -L/home/oracle/Desktop/storage/ -Wall main.c -o data -ldb_manager
gcc -o data main.c
to just this:
all:
gcc -Wall -c main.c
g++ -Wall -c db_manager.cpp
g++ main.o db_manager.o -o data
this is what I needed to do:
Supposing the C++ function is called Debug::Write(str)
Then in your hpp file do the following:
#ifdef __cplusplus
extern "C" void DebugTmp(char *str);
#endif
Then in the corresponding cpp file do this:
void DebugTmp(char *str)
{
Debug::Write(str);
}
Then in your C file where you call DebugTmp define the prototype:
void DebugTmp(char *str);
then call it as below:
static void MyFunction( void )
{
DebugTmp("This is debug trace\n");
}
I have 3 files; main.cpp (which contains main()), FileWriter.h, and FileWriter.cpp. I'm using g++ (version Debian 4.9.2-10) on Debian Jessie. My project contains .cpp files in '/root/dev/Practice/src/', and a single header (FileWriter.h) in '/root/dev/Practice/include/'. The compilation of the two object files works, but the linking to an executable complains about undefined reference to main(), although I do indeed have a seemingly valid one defined in 'main.cpp'.
Here's the output of my make file (which is in the root '/root/dev/Practice/' directory):
g++ -c -g -Wall -o src/FileWriter.o src/FileWriter.cpp
g++ -c -g -Wall -o src/main.o src/FileWriter.cpp
g++ src/FileWriter.o src/main.o -o bin/Practice
/usr/lib/gcc/i586-linux-gnu/4.9/../../../i386-linux-gnu/crt1.o: In function '_start'"
/build/glibc-J1NNmk/glibc-2.19/csu/../sysdeps/i386/start.S:111: undefined reference to 'main'
collect2: error: ls returned 1 exit status
Makefile:10: recipe for target 'bin/Practice' failed
Here's the contents of my main.cpp file:
#include <string>
#include <iostream>
#include "/root/dev/Practice/include/FileWriter.h"
int main() {
std::cout << "Hello!" << std::endl;
FileWriter * fw = new FileWriter("foofile");
fw->AddLine("CRAP!");
fw->AddLine("NO!");
return 0;
}
My FileWriter.h:
#ifndef FILEWRITER_H_
#define FILEWRITER_H_
#include <string>
#include <iostream>
class FileWriter{
public:
FileWriter(std::string);
~FileWriter();
void AddLine(std::string);
private:
std::string fileLocation;
std::ofstream *filestream;
};
#endif /* FILEWRITER_H_ */
...and my FileWriter.cpp:
#include "/root/dev/Practice/include/FileWriter.h"
#include <fstream>
// g++ linker error if 'inline' not included - why?
inline FileWriter::FileWriter(std::string fileName)
{
this->fileLocation = fileName;
const char * x = this->fileLocation.c_str();
this->filestream = new std::ofstream();
this->filestream->open(x, std::ios::out | std::ios::app);
}
inline FileWriter::~FileWriter()
{
this->filestream->close();
}
inline void FileWriter::AddLine(std::string line)
{
*this->filestream << line << std::endl;
}
This line:
g++ -c -g -Wall -o src/main.o src/FileWriter.cpp
should be:
g++ -c -g -Wall -o src/main.o src/main.cpp
I don't have access to this compiler, but in the past if you had main() in a C++ file you needed to "decorate" it with __cdecl
int __cdecl main() {
Try that? Or:
extern "C" int main() {
I am trying to overload global new and delete. So I have created a separate lib to keep both however when I try to use them i am seeing that my mehotds do not get called. Someone could tell me why and how I could fix, please?
Here is my code:
file my_operator.cpp
#include <cstdlib>
#include <cstdio>
void* operator new(size_t size)
{
puts("constructing");
void* p = malloc(size);
return p;
}
void operator delete(void *p) throw()
{
puts("deleting");
free(p);
}
file myclass.h
class clase
{
private:
int x;
public:
clase(int i):x(i){}
inline int getX(){return x;}
};
main.cpp
#include "myclass.h"
int main()
{
int k = 5;
int ret = 0;
clase* c = new clase(k);
delete c;
return ret;
}
what I have tried so far:
running this:
g++ -c my_operator.cpp -o my_operator.o && g++ main.cpp my_operator.o -o main
then launching ./main --> it works, my operators get called
however
running this:
g++ -c my_operator.cpp -o my_operator.o
ld -o my_operator.so my_operator.o -shared to create the .lib file
and then
g++ main
and finally running ./a.out does not work properly, my operators do not get called
Any clue?
Thanks in advance!
Your commands don't link your main with my_operator.so. You need something like the following:
g++ -Wall -Wextra -c -fPIC -o my_operator.o my_operator.cpp
g++ -shared -o libmy_operator.so my_operator.o
g++ -Wall -Wextra -c -o main.o main.cpp
g++ -o main main.o -lmy_operator
./main
Your main.cpp does not know that you overloaded the operators.
Put your overload operators in the header file.
Usefull links on this matter:
http://en.cppreference.com/w/cpp/memory/new/operator_new
http://www.cprogramming.com/tutorial/operator_new.html