Segmentation fault (pointer to an array)

This is a discussion on Segmentation fault (pointer to an array) within the C Programming forums, part of the General Programming Boards category; Hey, Having some issues with a pointer to an array. Code: GEOMOBJ **geometricObjects; numOfObjects = readTextFile(fileName, geometricObjects); I have this ...

  1. #1
    Registered User
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    Mar 2008
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    Segmentation fault (pointer to an array)

    Hey,

    Having some issues with a pointer to an array.

    Code:
    GEOMOBJ **geometricObjects;
    numOfObjects = readTextFile(fileName, geometricObjects);
    I have this function:
    Code:
    int readTextFile(char *filename, GEOMOBJ **p){
         *p = malloc(sizeof(GEOMOBJ) * numOfObjects);
         for (i = 0; i < numOfObjects; i++){
              *p[i] = i;
         }
    
         return numOfObjects;
    }
    I've determined that the segmentation fault is coming from the for loop. What I'm trying to accomplish is pass a pointer to an array to the function and have the function fill the array and return an integer.

  2. #2
    Just Lurking Dave_Sinkula's Avatar
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    Do you mean to do something like this?
    Code:
    GEOMOBJ *geometricObjects;
    numOfObjects = readTextFile(fileName, &geometricObjects);
    And this in the loop?
    Code:
     (*p)[i] = i;
    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
    Ex scientia vera
    Join Date
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    Quote Originally Posted by Lang View Post
    Hey,

    Having some issues with a pointer to an array.

    Code:
    GEOMOBJ **geometricObjects;
    numOfObjects = readTextFile(fileName, geometricObjects);
    I have this function:
    Code:
    int readTextFile(char *filename, GEOMOBJ **p){
         *p = malloc(sizeof(GEOMOBJ) * numOfObjects);
         for (i = 0; i < numOfObjects; i++){
              *p[i] = i;
         }
    
         return numOfObjects;
    }
    I've determined that the segmentation fault is coming from the for loop. What I'm trying to accomplish is pass a pointer to an array to the function and have the function fill the array and return an integer.
    I'm wondering - why are returning "numOfObjects" as if you're trying to keep track of how many were read, when you already know how many objects there are considering it must be globally defined, since you use the numOfObjects variable inside the function without it being defined inside its scope.

  4. #4
    Registered User
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    Mar 2008
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    11
    Yes that's done exactly what I need.

    Thanks muchly.

  5. #5
    C++まいる!Cをこわせ! Elysia's Avatar
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    Beware of compiler warnings!
    Passing a ** to a function with & will result in ***, which is not the ** the function wanted.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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