I'm attempting to write a simple program that calls a function written in a pair of Header and CPP files.
I'm doing this on a Raspberry Pi 3 Model B, and the Geany IDE v1.37.1.
Compile Command:
g++ -Wall -c "%f" -c test.cpp
Build Command:
g++ -Wall -o "%e" "%f" -o test test.cpp
main.cpp:
#include "test.h"
int main()
{
test_function();
return 0;
}
test.h:
#ifndef _test_h_
#define _test_h_
#include <iostream>
void test_function();
#endif
test.cpp:
#include "test.h"
void test_function()
{
std::cout << "hello world";
}
The code above compiles & builds fine, however attempting to run it yields the following error:
./main: not found
(program exited with code: 127)
Perhaps I am messing something up with the Compile & Build Commands?
Thank you for reading my post, any guidance is apprecaited!
Notice the compile command:
-o test
This means that the output binary will be test, so you can execute the application in your terminal or shell via ./test.
Related
running on version 11.1.0 of gcc and g++. Every time I run this code I run into issues it says std::numbers was not declared. I tried running g++ randomCodeWhileReading.cpp -o main-std=c++20 within my terminal (im running ubuntu linux) and still no change. Here is the code in question:
#include <iostream>
#include <numbers>
int main()
{
const long double pi {0};
const long double pi2 {0};
pi = std::numbers::pi_v<long double>;
pi2 = std::numbers::pi_v<long double>;
std::cout << pi << std::endl << pi2;
}
Just wanted to see the numbers module in action nothing else. (is it even called a module or is it a header file?)
EDIT 10/6/21:
The modifying a constant variable has been fixed. However, this code still wont run on my computer. Namely, the #include <numbers> does not seem to work on my machine it throws an error even when using -std=c++20. I am running gcc and g++ version 11.1 See error below:
gcc ex2_03.cpp -o -std=c++20
ex2_03.cpp: In function ‘int main()’:
ex2_03.cpp:22:65: error: ‘std::numbers’ has not been declared
22 | const double pond_diameter {2.0 * std::sqrt(pond_area/ std::numbers::pi)}; //find diameter by finding radius & multiplying by 2
|
however I was unable to replicate using godbolt.org (similar program not the same but uses as well). Clearly, it seems that this is an issue with my machine. How would I go about fixing this?
EDIT 10/8/21:
I ran the code again using more flags and changing -std=c++20 to -std=c++2a this was what was returned:
chris#chris-Aspire-E5-576G:~/Desktop/programming/c++/Learning$ ls
ex2_02 HelloWorld randomCodeWhileReading textbookExample1
ex2_02.cpp HelloWorld.cpp randomCodeWhileReading.cpp textbookExample1.cpp
ex2_02.o HelloWorld.o randomCodeWhileReading.o textbookExample1.o
ex2_03 main textbookDebug textbookOutputNameAndAge.cpp
ex2_03.cpp outputNameAndAge textbookDebug.cpp
ex2_03.o outputNameAndAge.o textbookDebug.o
chris#chris-Aspire-E5-576G:~/Desktop/programming/c++/Learning$ g++ -g -Wall -pedantic -std=c++2a -o randomCodeWhileReading.cpp
g++: fatal error: no input files
compilation terminated.
added the ls output to show I was in the correct directory.
EDIT 10/8/21 v2:
I used the following command and did not receive an error.
g++ randomCodeWhileReading.cpp -o main -std=c++20
Now just confused where the output went. By #nate's responses I assume it was sent to main? Just wanted to see a cout using std::numbers::pi
EDIT 10/8/21 v3:
All clear nate explained program can be ran by using ./main
EDIT 10/8/21 v4:
... I repeated the earlier command and got a error:
g++ randomCodeWhileReading.cpp -o main -std=c++20
cc1plus: fatal error: randomCodeWhileReading.cpp: No such file or directory
compilation terminated.
can someone explain what went wrong this time? (I am still in the same directory). After using ls it seems that the file is no longer in the directory seems to be deleted?
EDIT 10/8/21 v5:
I think the file got deleted when I was explaining the error to a friend and the wrong ways I was running the command lol. All good :D !
You need to compile with the extra flag -std=c++20.
Moreover, there is an error in your code: pi and pi2 are declared const, hence you cannot modify them after they are initialized. Use this instead:
#include <iostream>
#include <numbers>
int main()
{
const long double pi = std::numbers::pi_v<long double>;
const long double pi2 = std::numbers::pi_v<long double>;
std::cout << pi << std::endl << pi2;
}
Please try this code and this "compile" command on your machine with your version of g++:
/*
* TEST ENVIRONMENT: MSYS2 (Windows 10)
* COMPILER:
* g++ --version
* g++.exe (Rev5, Built by MSYS2 project) 10.3.0
* BUILD COMMAND:
* g++ -g -Wall -pedantic -std=c++2a -o x x.cpp
* <= NOTE: the correct command for C++ 20 compatibility in g++ 10.x is "-std=c++2a"
* RUN COMMAND:
* ./x
* 2pi=6.28319
*/
#include <iostream>
#include <numbers>
int main()
{
auto two_pi = 2*std::numbers::pi;
std::cout << "2pi=" << two_pi << '\n';
}
If it works, great. If it's the same, try "-std=c++20" and/or "-std=gnu++20". Look here for details: https://gcc.gnu.org/projects/cxx-status.html
See also:
https://stackoverflow.com/a/67453352/421195
https://stackoverflow.com/a/67406788/421195
Definitely "Update" your post to report back what happens. Be sure to copy/paste your commands and any error messages EXACTLY.
'Hope that helps.
I want to write a shared library and I want to get a compiler/linker error if I forgot to implement some functions.
Consider the following case:
test.h
class Test {
public:
Test();
};
test.cpp
#include "test.h"
main.cpp
#include "test.h"
int main() {
new Test();
}
If I create a library with this command gcc -c -fpic test.cpp && g++ -shared -o libtest.so -Wl,--no-undefined -Wl,--no-allow-shlib-undefined test.o there is no error message, but the library is broken. Is there a way to force the creation of a not broken library?
Edit: adding additional flag, but doesn't change result
These codes have been modified:
test.h :
class Test {
public:
Test();
};
test.cpp :
#include "test.h"
Test::Test(){} // you must implement the constructor
You must have to implement the constructor, and if not, you get an error "undefined reference to `Test::Test()'".
main.cpp :
#include <iostream>
#include "test.h"
using namespace std;
int main(void)
{
Test* t = new Test(); // you must define a pointer
cout << "test* was created: " << t << endl;
delete t;
t = nullptr;
return 0;
}
Now all the code is OK. Then we create a shared-library with the following command:
g++ -shared -o test.so -fPIC test.cpp
Finally, we compile the main.cpp file at the same time as referring to the test.so shared-library and get the exe output, by the command below:
g++ -g main.cpp test.so -o test.exe
I am testing C code using googleTest.
My test.cpp file look like that
#include <gtest/gtest.h>
extern "C" {
#include "list.h"
#include "list.c"
}
TEST(ListTest, singleInsertion) {
// some tests
}
int main(int argc, char **argv) {
testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
However trying to run the test from the terminal using
g++ test.cpp -lgtest gives Errors and warning as if the code being tested is C++ not C.
Error and warning Examples :
error: invalid conversion for mallocs and
warning: ISO C++ forbids converting a string constant to ‘char*'
how can I declare that my tested files are C not C++ ?
However trying to run the test from the terminal using g++ test.cpp -lgtest gives Errors and warning as if the code being tested is C++ not C.
That's because you are compiling it as C++ by using the g++ compiler. Use gcc to compile as C.
Unfortunately, this code won't compile as C - it'll choke on the google::InitGoogleTest() call because C doesn't recognize the :: scoping operator. I'm not familiar with this testing framework, but at first glance it looks like it's meant to be used with C++, not C.
The way to fix this is to remove the #include "list.c" directive
extern "C" {
#include "list.h"
}
and compile it separately as C:
gcc -c list.c
then compile your tester:
g++ -c test.cpp
and then link the object files with the library:
g++ -o test test.o list.o -lgtest
I installed the SystemC library 2.3.1 using this tutorial.
I wrote this hello world example:
//hello.cpp
#include <systemc.h>
SC_MODULE (hello_world) {
SC_CTOR (hello_world) {
}
void say_hello() {
cout << ”Hello World systemc-2.3.0.\n”;
}
};
int sc_main(int argc, char* argv[]) {
hello_world hello(“HELLO”);
hello.say_hello();
return(0);
}
and compiled with this command:
export SYSTEMC_HOME=/usr/local/systemc230/
g++ -I. -I$SYSTEMC_HOME/include -L. -L$SYSTEMC_HOME/lib-linux -Wl,-rpath=$SYSTEMC_HOME/lib-linux -o hello hello.cpp -lsystemc -lm
When I compile the code, I got a error with the library:
In file included from hello.cpp:1:0:
/usr/local/systemc230/include/systemc.h:118:16: error: ‘std::gets’ has not been declared
using std::gets;
^~~~
How can I solve this?
std::gets has been removed in C++11 (See What is gets() equivalent in C11?)
If you're building using C++11 flag (maybe with a g++ alias), you have to disable this line in systemc.h.
Replace
using std::gets;
with
#if defined(__cplusplus) && (__cplusplus < 201103L)
using std::gets;
#endif
As guyguy333 mentioned, in new versions, g++ is an alias for C++11.
so adding -std=c++98 would solve the problem.
The compile command may like
$ g++ -std=c++98 -lsystemc -pthread main.cpp -o main
You seem to have copy pased the code from webpage as it is. Please remember “” and "" are not the same thing. On line 8
cout << ”Hello World systemc-2.3.0.\n”;
replace it with
cout << "Hello World systemc-2.3.0.\n";
and on line 13
hello_world hello(“HELLO”);
replace it with
hello_world hello("HELLO");
And then execute the code again.
GoodLuck.
Below is a simple test.c code using curl:
#include <stdio.h>
#include <curl/curl.h>
int main(){
return 0;
}
To compile this code I use:
gcc test1.c -lcurl -o test1
For test1.c above compilation is correct. Now I would like to write some code using C++ libs (curlpp) and after that compile it.
#include <iostream>
#include <curlpp/cURLpp.hpp>
#include <curlpp/Easy.hpp>
#include <curlpp/Options.hpp>
int main(){
return 0;
}
To compile this code I tried:
g++ test2.cpp -lcurl -o test2
But I get this error:
fatal error: curlpp/cURLpp.hpp no such file or directory
compilation terminated.
This formula is not correct. The question is how to compile second code - test2.cpp?
You most likely forgot to install libcurlpp-dev.
You can find out where the required header files are located by running:
$ dpkg -S cURLpp.hpp
libcurlpp-dev:amd64: /usr/include/curlpp/cURLpp.hpp