CODEWITHSUNDEEP
ccastingcomparisoncompiler-warningschar-pointer
napkinsterror
napkinsterror

Reputation: 1965

Basic C cast warning pointer from int

Can someone tell me how to correct this warning/error. I am trying to get just the first character of a string to tell if it a "-".

Error: 

grep-lite.c:15:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   if(strcmp((char *) pattern[0],"-") == 0)
             ^
grep-lite.c:29:16: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   while(strcmp((char *) argv[index][0],"-"))
                ^

Source with warnings/errors:

Line 15: 

if (strcmp((char *) pattern[0],"-") == 0)

Line 29:

while (strcmp((char *) argv[index][0],"-"))

Complete Source: 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "grep-lite.h"

int main(int argc, char * * argv)
{
  //initailize variables
  int index = 1, lineNumber = 1;
  int oneMatchingLine = FALSE;
  int invertOpt = FALSE, lineNumOpt = FALSE, quietOpt = FALSE;
  char * pattern = argv[argc];

  //check if last arguement is invalid by starting with a '-'
  if(strcmp((char *) pattern[0],"-") == 0)
    {
      error(INVALID_PATTERN);
      return EXIT_ERROR;
    }

  //check if they asked for help
  if(strcmp(argv[index],"--help") == 0)
    {
      printHelpStatement();
      return EXIT_SUCCESS;
    }

    //walk through all options
  while(strcmp((char *) argv[index][0],"-"))
    {
      //find and set option
      if(processOptions(argv[index], &invertOpt, &lineNumOpt, &quietOpt))
    index++;
      //if invalid option fai
      else
    {
      error(INVALID_OPTION);
      return EXIT_ERROR;
    }
    }

  //walk through stdinput searching for pattern relationship
  while(feof(stdin) == 0)
    {
      //initialize
      char * thisLine = NULL;

      // get read line with fgets
      thisLine = fgets(thisLine, MAX_CHARACTERS, stdin);

      //find pattern location in thisLine
      char * patternLoc = strstr(thisLine, pattern);

      //check if we should print this line based of patternLoc and invertOpt
      if((!patternLoc != NULL && !invertOpt) || (pattenLoc == NULL && invertOpt))
    {
      //see if we should print this line
      if(!quietOpt)
        printLine(thisLine, lineNumOpt, lineNumber);
    }
      lineNumber++;
    }

Upvotes: 0

Views: 718

Answers (1)

Iharob Al Asimi
Iharob Al Asimi

Reputation: 53006

I will enumerate the problems I find in your code

  1. The correct usage of strcmp() exists in your code, in this line

    if (strcmp(argv[index],"--help") == 0)

    strcmp() is intended for string comparison, not character comparison, this

    if(strcmp((char *) pattern[0],"-") == 0)

    should be

    if (pattern[0] == '-')

    do not cast the variable to force compilation, instead find the actual cause for the compiler error/warning.

  2. You have a severe error, you don't allocate space for the thisLine char pointer, you must allocate memory via malloc() or just declare it as a char array like

    char thisLine[SOME_CONSTANT_NUMBER];

    Also, this

    while(feof(stdin) == 0)

    is never a good idea instead do it like this

    char thisLine[100];
while (fgets(thisLine, sizeof(thisLine), stdin) != NULL)

  3. You made another very common mistake, arrays in c are indexed from 0 to N - 1, so

    char *pattern = argv[argc]

    is wrong, because you are reading one element after the last, the correct code is

    char *pattern = argv[argc - 1]

    which will give you the last element.

Upvotes: 1

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