need help with malloc-free

This is a discussion on need help with malloc-free within the C Programming forums, part of the General Programming Boards category; this is my code : Code: #include<stdio.h> #include<stdlib.h> #include<string.h> #define JUMLAH 1000000 #define ISI 100 typedef struct _dodol { char ...

  1. #1
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    need help with malloc-free

    this is my code :
    Code:
    #include<stdio.h>
    #include<stdlib.h>
    #include<string.h>
    
    #define JUMLAH 1000000
    #define ISI     100
    
    typedef struct _dodol
    {
            char *string;
    } dodol;
    
    void testing(void)
    {
    	dodol **abc = (dodol**)malloc( JUMLAH * sizeof(dodol*) );
    	memset(abc, 0, JUMLAH * sizeof(dodol*));
            int i;
            char a[10];
    
            for(i=0; i<JUMLAH; i++) {
                    abc[i] = (dodol*)malloc(sizeof(dodol));
    		abc[i]->string = strdup("HALLLLLLLLLLOOOOOOOOOOOO");
            }
    
            for(i=0; i<JUMLAH; i++) {
    		free( abc[i]->string );
                    free( abc[i] );
            }
            free(abc);
    }
    
    int main()
    {
    	int i, j;
    	char a[10];
    
    	printf("ready to insert\n");
            scanf("%s",a);
    
    	j=1;
    	for(i=0; i<j; i++)
    		testing();
    
    	
     	printf("done free\n");
            scanf("%s",a);
    
            return 0;
    }
    If i run that code, it will be memory leak.
    But if i change j>1 (testing() running more than 1 time), the memory is cooled down.
    Whats wrong? >.<

  2. #2
    Woof, woof! zacs7's Avatar
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    Wow, you're allocating a lot of memory... not that it matters, but consider downsizing the test data.

    * Don't cast malloc, see the FAQ
    * Check if doesn't malloc fail before continuing, it returns NULL if it does.
    * testing() will only run once as it is.
    * What exactly are you trying to do? You could allocate an array of char * pointers... which point to strings which you also allocate.

  3. #3
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    Quote Originally Posted by zacs7 View Post
    Wow, you're allocating a lot of memory... not that it matters, but consider downsizing the test data.

    * Don't cast malloc, see the FAQ
    * Check if doesn't malloc fail before continuing, it returns NULL if it does.
    * testing() will only run once as it is.
    * What exactly are you trying to do? You could allocate an array of char * pointers... which point to strings which you also allocate.
    what i'm trying to do is to test why after i run testing() for 1 time, the memory is not going down (i use top to see my memory). It's supposed to be freed.
    But if i run testing() more than 1 time (try to change j>1), the memory is freed like it supposed to be.

    Thx

  4. #4
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by sleith View Post
    If i run that code, it will be memory leak.
    But if i change j>1 (testing() running more than 1 time), the memory is cooled down.
    Whats wrong? >.<
    Nothing is wrong. Just because you free() some memory does NOT mean it is returned to the system. It just makes it available for future allocation by malloc().

  5. #5
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    Quote Originally Posted by brewbuck View Post
    Nothing is wrong. Just because you free() some memory does NOT mean it is returned to the system. It just makes it available for future allocation by malloc().
    Hm..ok2 i undestand now. Thx

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