Segmentation Fault

**DeanWinchester** · 04-07-2012

I'm working on a filter, tried GDB but with no luck.

Code:

%{
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
FILE *trabtotal;
int tipo;
int i;
%}
%%


^\\(R|r)(E|e)(L|l)(A|a)(T|t)(O|o)(R|r)(I|i)(O|o)                             {if(tipo==1) {fprintf(trabtotal,"\\documentclass{report}\n\n");}
                                                                             if (tipo==2) {fprintf(trabtotal,"Esta expressão não existe em HTML");}}


%%


int yywrap()
{
   return 1;
}


int main(int argc,char *argv[])
{   printf("ola");
    for( i=argc; i>0; i--) {
    printf("%s\n", argv[i]) ;}
    if ((strcmp(argv[1],"-l")==0)) {tipo=1;}
    else{
    if ((strcmp(argv[1],"-h")==0)) {tipo=2;}
    }
    yylex();
    printf("Ficheiro convertido com Sucesso.\n\n");
    return 0;
}

This is my code.
Anyone sees anything that may cause this segmentation fault ?

It doesn't even printf("ola");

**stahta01** · 04-07-2012

With i equals argc; the following is not defined.

Code:

argv[i]

Further note: argv[0] can sometimes be a null pointer for some OSes.

Tim S.

**DeanWinchester** · 04-07-2012

Originally Posted by stahta01

With i equals argc; the following is not defined.

Code:

argv[i]

Further note: argv[0] can sometimes be a null pointer for some OSes.

Tim S.

Thanks for your reply Tim.
I believe I understand what you're saying but thing is my program isn't even printing "ola" so it's not even reaching the for.

**iMalc** · 04-07-2012

Originally Posted by DeanWinchester

Thanks for your reply Tim.
I believe I understand what you're saying but thing is my program isn't even printing "ola" so it's not even reaching the for.

Your conclusion is incorrect. Because the string "ola" does not contain a newline, the actual output is buffered for a short while and may not appear straight away.

argc[i] will be NULL and printing it will cause exactly what you are seeing. Fix the loop bounds.

**grumpy** · 04-07-2012

Originally Posted by stahta01

With i equals argc; the following is not defined.

Code:

argv[i]

Not true. The standard specifies that argv[argc] is the NULL pointer. That is not undefined. The result of dereferencing a NULL pointer is undefined.

Originally Posted by stahta01

Further note: argv[0] can sometimes be a null pointer for some OSes.

That is only true if argc is zero. If argc is greater than zero, then the standard specifies that argv[0][0] shall be the null (zero) character if the program name is not available from the host system. argv[0] cannot be the NULL pointer in that circumstance.

**memcpy** · 04-08-2012

> http://cboard.cprogramming.com/c-pro...yylex-%3B.html
> New yylex() problem

This is your third thread regarding virtually the same code snippet. I'm not even really sure how any of your code is supposed to the HTML replacement thing you described, nor am I sure what yylex() is. I also have no idea why every snippet has a bunch of trash characters between the #includes and the actual code.

**MK27** · 04-08-2012

Originally Posted by memcpy

nor am I sure what yylex() is. I also have no idea why every snippet has a bunch of trash characters between the #includes and the actual code.

See post #11:

http://cboard.cprogramming.com/c-pro...ml#post1099442

@Dean: use fprintf(stderr, ...) for debug output, it is not buffered, and don't forget the newlines.

Thread: Segmentation Fault

Thread Tools

Search Thread

Display