c++ in linux....

Well, I am getting into Linux, and decided to try to write a hello world app, for mthe tutorials on the site.

So, here is my code..

Code:

---

#include <iostream>

using namespace std;

int main()
{
  cout<<"HEY, you, I'm alive! Oh, and Hello World!\n";
  cin.get();
  return 1;
}

---

So I try compiling it with GCC and I get...

Code:

---

fhqwhgads@ryan1:~/EtopacSoftware> gcc HelloWorld.cpp
/tmp/cc1ADmAR.o(.text+0x25): In function `main':
: undefined reference to `std::cout'
/tmp/cc1ADmAR.o(.text+0x2a): In function `main':
: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
/tmp/cc1ADmAR.o(.text+0x35): In function `main':
: undefined reference to `std::cin'
/tmp/cc1ADmAR.o(.text+0x3a): In function `main':
: undefined reference to `std::basic_istream<char, std::char_traits<char> >::get()'
/tmp/cc1ADmAR.o(.text+0x66): In function `__static_initialization_and_destruction_0(int, int)':
: undefined reference to `std::ios_base::Init::Init[in-charge]()'
/tmp/cc1ADmAR.o(.text+0x95): In function `__tcf_0':
: undefined reference to `std::ios_base::Init::~Init [in-charge]()'
/tmp/cc1ADmAR.o(.eh_frame+0x11): undefined reference to `__gxx_personality_v0'
collect2: ld returned 1 exit status
fhqwhgads@ryan1:~/EtopacSoftware> gcc HelloWorld.cpp
/tmp/ccZKk43V.o(.text+0x25): In function `main':
: undefined reference to `std::cout'
/tmp/ccZKk43V.o(.text+0x2a): In function `main':
: undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
/tmp/ccZKk43V.o(.text+0x35): In function `main':
: undefined reference to `std::cin'
/tmp/ccZKk43V.o(.text+0x3a): In function `main':
: undefined reference to `std::basic_istream<char, std::char_traits<char> >::get()'
/tmp/ccZKk43V.o(.text+0x66): In function `__static_initialization_and_destruction_0(int, int)':
: undefined reference to `std::ios_base::Init::Init[in-charge]()'
/tmp/ccZKk43V.o(.text+0x95): In function `__tcf_0':
: undefined reference to `std::ios_base::Init::~Init [in-charge]()'
/tmp/ccZKk43V.o(.eh_frame+0x11): undefined reference to `__gxx_personality_v0'
collect2: ld returned 1 exit status

---

Any idea? I am not new to c++, just Linux.

you either need to add the proper flags to GCC or use G++ (which is just GCC with flags)

basically, it's trying to compile C code and you gave it C++ code.

I suggest trying this:

Code:

---

g++ test.cpp -Wall -W -pedantic -ansi -o test.exe

---

use g++ to compile. GCC understands c++, but by default it tries to link it with c libraries, hence all the undefined references.

Quote:

---

Originally Posted by major_small

you either need to add the proper flags to GCC or use G++ (which is just GCC with flags)

basically, it's trying to compile C code and you gave it C++ code.

I suggest trying this:

Code:

---

g++ test.cpp -Wall -W -pedantic -ansi -o test.exe

---

---

Why would I want to make an exe?

well, you are making an executable, but by convention, you don't include an extension for it. what he is showing off though, is that -o <filename> is how you specify the output file, because without it, the executables output name will simply be a.out

oooah ok. what would I put there for linux app?

the original code you posted compiles fine with just

Code:

---

g++ file.cpp

---

i suggest you read the man page on g++ to check out all the options you can use

>> oooah ok. what would I put there for linux app?
you dont have to put anything specific for a linux app. linux does not see files in terms of extensions, but rather permissions. so if you have a file named

foo

it will execute the same as foo as it would as

foo.bar
foobar
foo.exe
a.out

names dont matter.

so just put somthing descriptive for the '-o' option or leave it blank