compiling .cpp with gcc

Question

okay this I did accidentally , compiling .cpp using gcc and not g++

but I actually want to understand the console output, line by line, if it has any sense.

struct a{
   int pointer;
   int  rollno;
};

struct a student,*studentref;
studentref = &student;
studentref->rollno = 141; 
studentref->pointer = 8;

cout<<studentref->rollno<<") : "<<studentref->pointer<<endl;

compiling this code with gcc structpointers.cpp -o structp gives the following output:

sourab@sourab:/home/gbear/coding/learningds$ gcc structpointers.cpp -o structp
/tmp/ccXrq1Cv.o: In function `main':
structpointers.cpp:(.text+0x2e): undefined reference to `std::cout'
structpointers.cpp:(.text+0x33): undefined reference to `std::ostream::operator<<(int)'
structpointers.cpp:(.text+0x38): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&)'
structpointers.cpp:(.text+0x40): undefined reference to `std::ostream::operator<<(std::ostream& (*)(std::ostream&))'
/tmp/ccXrq1Cv.o: In function `__static_initialization_and_destruction_0(int, int)':
structpointers.cpp:(.text+0x6e): undefined reference to `std::ios_base::Init::Init()'
structpointers.cpp:(.text+0x7d): undefined reference to `std::ios_base::Init::~Init()'
collect2: error: ld returned 1 exit status

Your question should be "linking c++ program with gcc", compiling .cpp by gcc pretty fine - gcc determines mode by file extension. — Slava, Apr 26 '17 at 11:42

score 2 · Accepted Answer · edited May 23 '17 at 12:25

2

The most egregious difference between calling g++ and gcc on a .cpp file is that g++ automatically links in the C++ standard library, while gcc does not; all the errors you see are linker errors of missing references to stuff that is provided by the C++ standard library.

(notice that this isn't the only difference; see this question for details)

edited May 23 '17 at 12:25

Community

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answered Dec 25 '15 at 16:19

Matteo Italia

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score 0 · Answer 2 · answered Apr 26 '17 at 11:39

g++ and gcc are compiler drivers of GNU compiler collection, they have backends which are connected automatically once compilation mode in up. The errors like "

structpointers.cpp:(.text+0x2e): undefined reference to `std::cout'

are link errors,since you have used gcc to compile cpp,the standard libraries specifically for cpp are not present, so it could not find syntax like std::cout etc.

you can also refer to : compiling with g++

compiling .cpp with gcc

2 Answers2