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I am coding a program which takes a text file as an input, makes the index of the words of it and prints the output(the index) in a file and in the screen.

the input file may be huge. but we KNOW that the maximum variety of the words used in the text file is 200. we don't know what's the maximum of lines and characters of each word. so I should reserve a large number for them. I took the maximum of line 1000 and the maximum characters of each word 100.

I am programming in Turbo C and (I am forced to use that). the compiler allocates just 64kb memory (with the size of the compiler included) and so I have to use MALLOC.

my program is supposed to work in this algorithm: it reads the input file line by line with fgets. then in the current line, it reads word by word with strtok. so far I have the xth word in yth line. I want to put the words in an array of pointers. so I need a char * word[200]. and I want to show how many times, which word is repeated in which line. so I need a int index [200][1000]. if in yth line, the xth word is existed I would do index[x][y]++.

so now I need to allocate MALLOC memory to these char * word[200] and int index[200][1000] . Can anyone help? I tried all the answers to these question and none of them helped.

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    As to the error, move the declaration out of the loop or move it inside a block. Also, do NOT cast the return value of malloc(). Commented Dec 2, 2013 at 18:24
  • It's quite too obvious that it doesn't work.and for sure I know that. I just coded that so that the readers understand what I mean. Commented Dec 2, 2013 at 18:25

3 Answers 3

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You don't quite have malloc right. Your malloc(100) is only allocating 100 bytes. You need

char * words[i] = malloc(sizeof(char *) * 100);

This allocates 800 bytes (100 elements of 8 bytes (size of a pointer) each).

Similarly, in the second malloc, you want two integers, you need

int index[i][j] = malloc(sizeof(int *) * 2);

You shouldn't cast to a pointer; it returns a void pointer, which is implicitly cast to whatever type of pointer you need just by virtue of the assignment.

http://www.cplusplus.com/reference/cstdlib/malloc/

FURTHERMORE:

Additionally, you're trying to stuff 2 bytes into an integer pointer or 4 bytes (100-96 = 4; the 96 is 8 * 12) into a character pointer. I have no idea in the world what that will do. The BEST you can hope for is that you'll just lose the memory somewhere and effectively have 12 character pointers and 2 memory leaks.

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4 Comments

@ Jonah Nelson: thanks really. SO won't go on without u kind people who try to spot the exact problem instead of criticizing others' knowledge.
There are platforms where int is 16 bits :-)
Find me a platform where (int *) is 16 bits, and then it'll be pertinent to my response.
Sorry, I thought the array will be for storing int, not int*
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If I understand you

In the first loop, I want to define an array of 200 pointers that each pointer, points to an array of char blocks. I want each pointer, points to an array of maximum 100 bytes. Meaning 100 char blocks

char **words = NULL;
int i;
words = malloc(sizeof(char*) * 200);
for(i = 0; i < 200; i++) {
    words[i] = malloc(100);
}

There's allocating 200 words with 100 bytes size here.

In the second loop, I want to define a 2D array of int blocks that each block is maximum 2 bytes. meaning 200 * 1000 int blocks.

int **index = NULL;
int i;

index = malloc(sizeof(int*) * 200)
for (i = 0; i < 200; i++) {
    index[i] = malloc(sizeof(int) * 1000);
}

Here you allocate 200x1000 int array.

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6 Comments

Yes. index is 2d array. You can access to any element (which has int type) by index[i][j]
and I want to use the array of word and and the 2D array of index at the same time. we are addressing the both of them in first lines to NULL. it would make trouble?
@MelikaBarzegaranHosseini Do you want to use an array of "words" with size 200x100 (200 words per 100 character) and 2D array of ints (200 x 1000 ints) so that each int points to each character from first array?
no they are not related. I am coding a program which has a file as an input, creates the index of it and prints the output in the screen and in a output file. I need words array to hold words of the input file in it. and I need the index 2D array to hold which word, how many times is repeated in which line. 200 words * 1000 sentences. each block in this 2D array will show how many times this word is repeated in this sentence.
You seem to not store sentences. You want to ouptut "word XYZ is cited 2 times in sentences 42 and 1 time in sentence 512" ?
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char * words = malloc(200*100);
int * index = malloc(200*1000*sizeof(int));

// word[i*200+j] : character j in word i
// index[i*200+j] : int at index i,j

alternatives:

// mallocing an array for storing a maximum of 200 malloced words
char ** words = malloc(200*sizeof(char*));
// adding a new word, at index i, which is pointed to by pszNewWord (null terminated)
words[i] = strdup(pszNewWord);
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17 Comments

so by coding such as above, we don't have access to index as a 2D array?
you know it doesn't help as I don't know how much characters each word contains. just the maximum is 200.
No, we don't but we can access a given int with i and j. Things will be way much simpler without malloc. Why do you need malloc?
200 is the word count, 100 is the maximum characters count for one word. What is the problem?
I am coding a program which gives a file as an input, creates the index of it and prints it in a file as an output. I know that the variety of words is maximum 200. but I don't know how large the words are. how large the sentenses are. that's why I need to use malloc.
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