What is wrong with this statement???

This is a discussion on What is wrong with this statement??? within the C Programming forums, part of the General Programming Boards category; char * p1; char * p2; char * tmp; p1=(char *) malloc(sizeof(char)); p2=(char *) malloc(sizeof(char)); *p1='A'; *p2='B'; tmp=p1; p2=tmp;...

  1. #1
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    What is wrong with this statement???

    char * p1;
    char * p2;
    char * tmp;
    p1=(char *) malloc(sizeof(char));
    p2=(char *) malloc(sizeof(char));
    *p1='A';
    *p2='B';
    tmp=p1;
    p2=tmp;

  2. #2
    Just Lurking Dave_Sinkula's Avatar
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    Using [code] [/code] tags makes posted code easier to read.
    Code:
    char * p1;
    char * p2;
    char * tmp;
    p1=(char *) malloc(sizeof(char));
    p2=(char *) malloc(sizeof(char));
    *p1='A'; /* Possible use of null pointer 'p1' in argument to operator 'unary *' */
    *p2='B'; /* Possible use of null pointer 'p2' in argument to operator 'unary *' */
    tmp=p1;
    p2=tmp;  /* Creation of memory leak in assignment to 'p2' */
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  3. #3
    Skunkmeister Stoned_Coder's Avatar
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    read the FAQ to see why casting the return value of malloc is generally considered a bad idea.
    Free the weed!! Class B to class C is not good enough!!
    And the FAQ is here :- http://faq.cprogramming.com/cgi-bin/smartfaq.cgi

  4. #4
    Confused Magos's Avatar
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    FAQ

    If the return of malloc is cast then the error which would be flagged is hidden, resulting in a difficult to find bug.
    What error? Failure to allocate? There is still a NULL pointer that is returned, right?
    MagosX.com

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  5. #5
    Just Lurking Dave_Sinkula's Avatar
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    >There is still a NULL pointer that is returned, right?

    In the context from which it was taken -- when stdlib.h is not #included (for a pre-C99 compiler) -- no: malloc would be implicitly declared as returning an int -- which is not a pointer. I think Joona does a good job with an explanation, but the rest of the thread is here.
    7. It is easier to write an incorrect program than understand a correct one.
    40. There are two ways to write error-free programs; only the third one works.*

  6. #6
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    ok, i got it thanks.

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