/prog/ - ENTERPRISE UNICODE DETECTOR AND READER

Name: Anonymous 2012-01-12 20:35



#include <stdio.h>



int main(void) {

  char buff[256];

  char c;

  FILE *f;



  f = fopen("filename", "r");

  c = fgetc(f);

  if(c < 0) {

    fclose(f);

    system("type filename > filename.tmp");

    f = fopen("filename.tmp", "r");

  }

  else {

    rewind(f);

  }



  while(fgets(buff, 256, f) != NULL)

    puts(f);



  fclose(f);

  

  return(0);

}

Name: Anonymous 2012-01-12 22:31

>>17
C99 7.19.5.3.8 The fopen function returns a pointer to the object controlling the stream. If the open operation fails, fopen returns a null pointer.
So what happens if fopen() returns a NULL pointer and you call fgetc() on it?
C99 7.1.4.1 Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (such as a value outside the domain of the function, or a pointer outside the address space of the program, or a null pointer, or a pointer to non-modifiable storage when the corresponding parameter is not const-qualified) or a type (after promotion) not expected by a function with variable number of arguments, the behavior is undefined.
The Standard provides no exceptions for fgetc(), so it's undefined behavior.

Name: Anonymous 2012-01-12 22:32

undefined behavior

ENTERPRISE UNICODE DETECTOR AND READER

1 Name: Anonymous 2012-01-12 20:35

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Name: Anonymous 2012-01-12 20:35

Name: Anonymous 2012-01-12 22:31

Name: Anonymous 2012-01-12 22:32