SEGFAULT when declaring input file with ifstream

DrSchwartz

Hi there,
I have to read in from file, and then process it. It looks like this.

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#include <iostream>

#include <string>

#include <fstream>

using namespace std;

...

int main()

{

ifstream in_file ("list", ifstream::in);

while (!in_file.eof()){

        in_file.read(buffer,16);

   ...

}

in_file.close();

return 0;

}

It compiles OK, but when I run the program, it crashes with SEGFAULT on the line with ifstream in_file ("list", ifstream::in);
GDB shows:

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 Program received signal SIGSEGV, Segmentation fault.

main () at HashTest.cpp:14

14      ifstream in_file ("list", ifstream::in);

and backtrace shows this stupid thing:

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 (gdb) backtrace full

#0  main () at HashTest.cpp:14

        buffer = "\bТъщВТ╞\004\b(&╬ЪP\212\004"

        table = Cannot access memory at address 0xffbe2638

(gdb)

What is the reason?:(

newb16

You omitter buffer variable definition; I declared buffer as char[100] and it worked.

zodilla58

Segmentation faults are generally because a pointer of yours is either null or points to some random memory (probably never initialized) or points to memory that was deleted. You are storing read file in buffer which is not initialized and so it is showing error!

DrSchwartz

Quote:

Originally Posted by zodilla58

Segmentation faults are generally because a pointer of yours is either null or points to some random memory (probably never initialized) or points to memory that was deleted. You are storing read file in buffer which is not initialized and so it is showing error!

But the buffer is already allocated, just after main(){
char buffer[16];
i just omitted that part when posting code snippet. so the reason should be different

JosAH

Quote:

Originally Posted by DrSchwartz

But the buffer is already allocated, just after main(){
char buffer[16];
i just omitted that part when posting code snippet. so the reason should be different

You should've posted a compiling, running and small example that exhibits the unwanted behaviour; now you've just shown us an incomplete piece of code that just leaves us guessing.

kind regards,

Jos

DrSchwartz

Thanks for your replies. OK, here is the code. I cannot imagine how I fault in this kind of plain simple program. (Note to avoid possible question: there IS file "list" in the directory of program)

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#include <iostream>

#include <string>

#include <fstream>

#include "GeneralHashFunctions.h"

using namespace std;

#define CHARBUFSIZE 16

int main()

{

char buffer[CHARBUFSIZE];

int i=0;

ifstream in_file ("list", ifstream::in);

if (in_file.fail() )

{

        cout << "Can't open input file" << endl;

        return -1;

}

while (!in_file.eof()){

        in_file.read(buffer,16);

        std::string key = buffer;

        std::cout<<RSHash(key)<<std::endl;

        i++;

}

in_file.close();

return 0;

}

One more thing, when I run program through GDB, it says:

Quote:

warning: Lowest section in system-supplied DSO at 0xffffe000 is .hash at ffffe0b4

what does this mean?

SEGFAULT when declaring input file with ifstream

re: SEGFAULT when declaring input file with ifstream

re: SEGFAULT when declaring input file with ifstream

re: SEGFAULT when declaring input file with ifstream

re: SEGFAULT when declaring input file with ifstream

re: SEGFAULT when declaring input file with ifstream

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