help with structs and malloc!

I'm writing a header files and I must be allocating the space wrong because I'm trying to do a linked list but the nodes keep changing.

table.h (some of these I haven't written yet)

Code:

---

#ifndef TABLE_H_
#define TABLE_H_
#include <stdio.h>

        struct lineNode;

        struct entry;

        struct table;

        /* returns an empty table */
        struct table * newTable ( );

        /* returns the result of adding a definition for the given symbol
          in the line with the given number to the table */
        struct table * addDef (char * symbol, int lineNum, struct table * symbols);

        /* returns the result of adding a use of the given table in the line
          with the given number to the table */
        struct table * addUse (char * symbol, int lineNum, struct table * symbols);

        /* print the table, in the format described above, to the given file */
        void printTable (struct table * symbols, FILE * out);



#endif /* TABLE_H_ */

---

table.c

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include "table.h"

struct lineNode {
  int lineoccur;
  struct lineNode *next;
};

struct entryNode {
        struct entryNode *next;
        struct entry *row;
};

struct entry {
      char * symbol;
      int linedef;
      struct lineNode *occur;
};

struct table {
      int entrycount;
      struct entryNode *first;
};

        /* returns an empty table */
struct table * newTable( ) {
      struct table * table1 = malloc(sizeof(struct table));
      table1->entrycount = 0;
      return table1;
}

struct table *firstSymbol(struct table * symbols) {
        printf("the symbol is %s\n", symbols->first->row->symbol);
}

        /* returns the result of adding a definition for the given symbol
          in the line with the given number to the table */
struct table * addDef (char * symbol, int lineNum, struct table * symbols){

        printf("adding %s\n", symbol);
        printf("entrycount is %d\n", symbols->entrycount);
        if (symbols->entrycount == 1)
                printf("should be word1 %s\n", symbols->first->row->symbol);

        struct entry *newEntry = malloc(sizeof(struct entry));
        newEntry->symbol = symbol;
        newEntry->linedef = lineNum;
        struct entryNode *newEntryNode = malloc(sizeof(struct entryNode));
        newEntryNode->row = &newEntry;

        //somewhere here the symbol in the first node changed to "word2"
        if (symbols->entrycount == 1)
                        printf("again should be word1 %s\n", symbols->first->row->symbol);

        if (symbols->entrycount == 0) {
                symbols->first = &newEntryNode;
                symbols->entrycount = 1;
                printf("should be word1 %s\n", symbols->first->row->symbol);
        }
        else {
                printf("2should be word1 %s\n", symbols->first->row->symbol);
                struct entryNode *nEntryNode = malloc(sizeof(struct entryNode));
                nEntryNode = symbols->first;
                int s = symbols->entrycount;
                while (s != 1) {
                        nEntryNode = nEntryNode->next;
                        s--;
                }
                nEntryNode->next = &newEntryNode;

        }
        printf("should still be word1 %s\n", symbols->first->row->symbol);
        return symbols;
}

        /* returns the result of adding a use of the given table in the line
          with the given number to the table */
//struct table * addUse (char * symbol, int lineNum, struct table * symbols) {
//    return symbols;
//}

        /* print the table, in the format described above, to the given file */
void printTable (struct table * symbols, FILE * out) {
    struct entryNode *n = symbols->first;
    printf("%s\t\n", n->row->symbol);
    printf("%d\t\n", n->row->linedef);
    printf("here it is\n");
}

---

tabletest.c

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include "table.h"

main() {


    struct table *p = newTable();
    p = addDef("word1", 1, p);
    p = addDef("word2", 2, p);
    printTable(p, "out.txt");

    return 0;

}

---

This is the output I get on eclipse:
adding word1
entrycount is 0
should be word1 word1
should still be word1 word1
adding word2
entrycount is 1
should be word1 word1
again should be word1 word2
2should be word1 word2
should still be word1 word2
0Ì"
2280496
here it is

Why is it printing out a weird symbol and letter? And if I'm using malloc how did the contents change to word2 when I was creating new nodes and not assigning anything to it?

Thanks in advance.

How about assigning all members of the declared structs. By leaving out some you can expect the weird symbols in the output

Code:

---

struct table * newTable( ) {
      struct table * table1 = malloc(sizeof(struct table));
      table1->entrycount = 0;
      return table1;
}

---

Where's the assignment for struct entryNode *first member of struct table.

hmm I don't know if that makes a difference... I was checking the addresses of the places where the first->symbol is stored, when I have this in addDef

Code:

---

        printf("2should be word1 %d\n", symbols->first->row->symbol);
        }
        struct entry *newEntry = (struct newEntry*) malloc(sizeof(struct entry));
        printf("address is %d\n", newEntry);

        if (symbols->entrycount == 1) {
                                        printf("3here again should be word1 %d\n", symbols->first->row->symbol);
                                        printf("4here again should be word1 %s\n", symbols->first->row->symbol);
        }

        newEntry->symbol = symbol;
        newEntry->linedef = lineNum;

        if (symbols->entrycount == 1) {
                printf("5here again should be word1 %d\n", symbols->first->row);
                printf("6here again should be word1 %s\n", symbols->first->row->symbol);
        }

---

part of the output is:
1should be word1 word1
2should be word1 134515162
address is 165683272
3here again should be word1 0
4here again should be word1 (null)
5here again should be word1 165683272
6here again should be word1 word2

So it seems like after I initialized newEntry it also changed symbols->first->row->symbol? and later set it to the newEntry? how did that happen?

your initial code in your first post compiled with the following warnings:

Quote:

---

Originally Posted by gcc

table.c: In function `addDef':
table.c:31: warning: assignment from incompatible pointer type
table.c:38: warning: assignment from incompatible pointer type
table.c:51: warning: assignment from incompatible pointer type

---

referring to lines which do something like:

Code:

---

newEntryNode->row = &newEntry;

---

newEntryNode->row is of type struct entry * but your passing type of struct entry **. fixing these warnings produced correct output for me.

also, for every malloc call you must have a corresponding free call; your program has a few memory leaks in it.

wow ok fixing the warnings seemed to have worked. thanks!

what do you mean I have to free the malloc? I want to add to the linked list so how else would I keep creating new nodes and add to the existing ones?

also:

Code:

---

struct entryNode *nEntryNode = malloc(sizeof(struct entryNode));
nEntryNode = symbols->first;

---

this is another memory leak because you allocate some memory and assign the address of this allocated memory to nEntryNode. however, the next line you assign a different value to nEntryNode, thus loosing the address of the initial memory you allocated, and you now have no way of freeing or either referencing this memory. basically, the malloc call is not needed, just do:

Code:

---

struct entryNode *nEntryNode = symbols->first;

---

Quote:

---

wow ok fixing the warnings seemed to have worked. thanks!

---

make sure to pay attention to all compiler output, warnings are just that: warnings. its saying "ATTENTION: did you mean to do this? if not, the behaviour might not be what you intended".

Quote:

---

what do you mean I have to free the malloc?

---

if you dont fully understand what dynamic memory is (in particular, the calls to malloc and free in the C language), i would suggest reading an overview of it (or check the FAQ on this site, there should be an entry for this topic). when you call "malloc", your telling the OS "i want N bytes of memory allocated to me, and i will manage it completely". the OS searches for a continuous block of N available bytes of RAM, and if it finds some it gives it to you. if it doesnt find some, it returns NULL (therefore you should check the return value of malloc) and your program doesnt get this memory (and it should exit with an error or appropriate message). if you get the memory, you can do whatever you want with it. when you are done with it, you must free the memory with the "free" function call. if you dont "free" it, when your program is done running, the OS still has this memory reserved for your program, however its not being used--its wasted and you cant do anything about it. on some OSs, this memory leak continues until the machine is restarted. there may be other OSs or some tools to use to clean this stuff up (though i dont know of any).

Quote:

---

I want to add to the linked list so how else would I keep creating new nodes and add to the existing ones?

---

the else block in your addDef function should be changed to something like:

Code:

---

struct entryNode *nEntryNode = symbols->first;
while ( nEntryNode->next != NULL ) { // use either "0" or "NULL", if you use "NULL" then define it or include the header its defined in (if there is one, i forget)
      nEntryNode = nEntryNode->next;
}
nEntryNode->next = newEntryNode;

---

this loop iterates over all nodes, starting at the first, and stopping when this node does not have a next, which means its at the end of the list. you then add your new node at this spot ("next"). this logic assumes that whenever you create a newNode, you assign its next to "0" or "NULL', otherwise the algorithm doesnt work. this is usually how linked lists are implemented. therefore, you need to make sure to set the next to this value whenever you create one.

tell us if you understand this, otherwise it is completely useless if you can copy and paste it without understanding (in which case i will wish i wouldnt have given you the information).

ok so I made all those fixes, and now I'm writing another function addUse, which adds a node containing a number to the *occur list of entry objects to the table.

Code:

---

struct table * addUse (char * symbol, int lineNum, struct table * symbols) {

       
        //when I add in this printf line, it runs fine
        printf("starting to add %s %d\n", symbol, lineNum);
        struct entry *nEntry = symbols->first;
        while ( nEntry->symbol != symbol) {
                if (nEntry->next == NULL) {
                        printf("should not be null\n");
                        break;
                }
                nEntry = nEntry->next;
        }
        struct lineNode *o = nEntry->occur;
        while ( (o->next != NULL) && (o->lineoccur != -1) ) {
                o = o->next;
        }

        if (o->lineoccur == -1) {
                o->lineoccur = lineNum;
        }
        else {
                struct lineNode *newLineNode = malloc(sizeof(struct lineNode));
                newLineNode->lineoccur = lineNum;
                o->next = newLineNode;
        }

        return symbols;
}

---

this is the printTable function that is printing out the table

Code:

---

void printTable (struct table * symbols, FILE * out) {
    struct entry *n = symbols->first;

        while (n != NULL) {
            printf("%s\t", n->symbol);
            printf("%d\t", n->linedef);

            struct lineNode *nline = n->occur;

            while ((nline != NULL) && (nline->lineoccur != -1)) {
                    printf("%d\t", nline->lineoccur);
                    nline = nline->next;
            }
            printf("\n");

            fprintf(out, "%s\t", n->symbol);
            fprintf(out, "%d\t\n", n->linedef);
            n = n->next;
    }

        printf("finished printing \n");
}

---

If I don't have the print line, this is what I get on eclipse:
13 [main] hw3 13744 _cygtls::handle_exceptions: Exception: STATUS_ACCESS_VIOLATION
930 [main] hw3 13744 open_stackdumpfile: Dumping stack trace to hw3.exe.stackdump

how can a print statement change it?

If I add in the print line:
starting to add word1 11
starting to add word2 5
starting to add word2 6
starting to add word2 7
starting to add word2 8
starting to add word2 9
starting to add another word! 3
starting to add another word! 4
word1 1 11
word2 2 5 6 7 8 9
another word! 12 3 4
finished printing

You never set 'newLineNode->next' to anything.


Quzah.

thanks for all the help I've gotten! it's very useful.

now I'm writing a processLines that will assign each word in a line read in to addDef or addUse to add to my table.

processLines

Code:

---

int processLine(char *s, int linecount) {
        printf("string is %s\n", s);

        if (emptyLine(s) == -1) {
                return 0;
        }
        else {
                char word[MAXSYMBOL];
                int pos = 0;
                char c = *s;
                //hi
                int wordon = 0;
                printf("c is %c\n", c);
                while (c != '\n' && c != EOF && c!='#') {
                        //when I add this line in it starts to infinite loop
                        printf("c is %c\n", c);
                        if (c == ' ' && wordon == 0) {
                                s++;
                                c = *s;
                        }
                        else if (c != ' ' && wordon == 0){
                                word[pos] = c;
                                s++;
                                pos++;
                                c = *s;
                                wordon = 1;
                        }
                        else if (c == ' ' && wordon == 1) {
                                printf("word ended %s\n", word);
                                wordon = 0;
                                s++;
                                c = *s;
                        }
                        else {
                                word[pos] = c;
                                pos++;
                                s++;
                                c = *s;
                        }

                }
                return 0;
        }

}

---

I am calling processLines in my main() with the line "abc " from my input file. The first time the c prints it prints fine, 'a' but then in the while loop it starts to infinite loop.

here is emptyLine

Code:

---

int emptyLine (char line[]) {
    int i=0;
    while (1) {
            printf("line[i] is %c\n", line[i]);
          if (line[i] == '\0' || line[i] == '\n') {
            return -1;
          }
          else if (line[i] != ' ') {
                  printf("should not be empty\n");
              return i;
          }
          else {
              i++;
          }
    }
}

---

How do you plan to get out of your while loop? You can't. You should maybe check for the end of string character (which is '\0', not EOF).

ok I fixed the '\0' problem by adding two more cases:

Code:

---

int processLine(char *s, int linecount, struct table *p) {
        printf("string is %s\n", s);
        char words[MAXSYMBOL];

        char* word = words;

        char* word2 = word;

        if (emptyLine(s) == -1) {
                return 0;
        }
        else {
                //char word[MAXSYMBOL];
                int pos = 0;
                char c = *s;
                //hi
                int wordon = 0;
                printf("c is %c\n", c);
                while (c != '\n' && c != EOF && c!='#') {
                        printf("c is %c\n", c);
                        if (c == ' ' && wordon == 0) {
                                s++;
                                c = *s;
                        }
                        else if (c != ' ' && wordon == 0){
                                *word = c;
                                word++;
                                s++;
                                pos++;
                                c = *s;
                                wordon = 1;
                        }
                        else if (c == '\0' && wordon == 0) {
                                *word = '\0';
                                break;
                        }
                        else if (c == '\0' && wordon == 1) {
                                printf("line ended %s\n", word);
                                *word = '\0';
                                addDef(word2, linecount, p);
                                break;
                        }
                        else if (c == ' ' && wordon == 1) {
                                *word = '\0';
                                printf("word ended2 %s\n", word);
                                wordon = 0;
                                s++;
                                c = *s;
                        }
                        else {
                                *word = c;
                                word++;
                                pos++;
                                s++;
                                c = *s;
                        }

                }

                return 0;
        }

}

---

I want to read in every word, add the word to the table, and when I reach '\0' stop, so I switched over to using pointers. However, now I get a jumble when I print out the word I read. Why is this?

c is a
c is a
c is b
c is c
c is
c is
line ended ø]¿KÑ°À¤À

Ô]¿KÑ°À¤À
1
finished printing
stack trace 2
Ô]¿ø]¿Ø³ 1 2

I should have had "abc" added instead.

Quote:

---

Originally Posted by nadroj

if you dont "free" it, when your program is done running, the OS still has this memory reserved for your program, however its not being used--its wasted and you cant do anything about it. on some OSs, this memory leak continues until the machine is restarted. there may be other OSs or some tools to use to clean this stuff up (though i dont know of any).

---

Isn't it that the when the program has executed properly, the allocated memory is automatically freed and can be used somewhere else?

Quote:

---

Originally Posted by BEN10

Isn't it that the when the program has executed properly, the allocated memory is automatically freed and can be used somewhere else?

---

but I haven't used malloc in this function?

You need to figure out why you didn't get "word ended2" -- you are soooo not going to get the word printed on the line, since by definition word is completely blank (your word is in word2, not word). But I don't see any reason why you didn't get in there, so you need to see what happened to wordon. And of course if you didn't get into that particular bit of code, obviously nothing was added to your table. Are you sure you have a space at the end of your word? (Edit: And of course, having code that doesn't add a word to the list if there's not a space on it is probably an error on its own, so when the character is \0 and wordon is 1, you should probably add to the table there too.)

I think something in my printTable() is messing it up:

Code:

---

void printTable (struct table * symbols, FILE * out) {
    struct entry *n = symbols->first;
    printf("%s\n", symbols->first->symbol);
    printf("%s\n", n->symbol);
    //line above prints %s and then a newline

        while (n != NULL) {
            printf("%s", n->symbol);
        //this line prints a newline even though I didn't give it anything
            printf("after");
            printf("%d\t", n->linedef);

            struct lineNode *nline = n->occur;

            while ((nline != NULL) && (nline->lineoccur != -1)) {
                    printf("%d\t", nline->lineoccur);
                    nline = nline->next;
            }
            printf("\n");

            fprintf(out, "%s\t", n->symbol);
            fprintf(out, "%d\t\n", n->linedef);
            n = n->next;
    }

        printf("finished printing \n");
}

---

In tabletest.c I am using a nextWord function to get the next word and add to table:

Code:

---

int nextWord (char *str, int pos, char *word, int linecount, struct table *p) {

        printf("string is %s\n", str);
        if (emptyLine(str)== -1) {
                printf("empty line\n");
                return -1;
        }


    int i=0;

    while (1) {
              if (*str == '\n' || *str == '\0' || *str == '#')
              return -1;
          else if (i == pos) {
                  break;
          }
              else {
                  i++;
                  str++;
          }
    }
    printf("str is now %s\n", str);
    int r = pos;

    char* word2 = word;
    int j;
    for (j=0; *str!='\n' || *str!=EOF; str++) {
            if (*str != ' ') {
                char c = *str;
                while (c != '\n' && c != ' ' && c!='\0') {
                          r++;
                          *word = c;
                          word++;
                          str++;
                          c = *str;
            }
                *word = '\0';
                printf("word is %s\n", word2);

                char last = *--word;
                //fprintf(output, "%c \n", last);
            if (last != ':') {
              printf("adding use\n");
              addUse(word2, linecount, p);
              printTable(p, output);
                  return r;
            }
            else {
                    printf("adding def\n");
                    addDef(word2, linecount, p);
                    printTable(p, output);
                    return r;
            }
              printf("here %s  %d\n", word2, linecount);
            break;
            }
            else {
                r++;
            j++;
            }
    }
    word = word2;
    return r;
}

---

my main is just looping and reading one line in the input file, "abc"

Code:

---

main() {

        printf("stack trace 1\n");
        input = fopen("table.test", "r");
        output = fopen("table.out", "w");

        char *s;
        int linecount = 1;
        int pos;
        char line[MAXLINE];
        char word[MAXSYMBOL];
        struct table *p = newTable();

        printf("stack trace 1\n");


        //processLine(s, 1, p);
        //printTable(p, output);

        /*while (s = newLine(input)) {
                printf("reading input: %s\n", s);
                processLine(s, linecount);
                linecount++;
        }*/


        while (s = newLine(input)) {
                printf("reading input: %s\n", s);
                pos = 0;
                while (1) {
                        printf("should go in here\n");
                        if ((pos = nextWord (s, pos, word, linecount, p)) == -1)
                                break;
                        printf("pos is %d\n", pos);
                        printTable(p, output);
                }
                linecount++;
        }

---

Is there any reason why printTable would print out a newline and mess up the formatting?

stack trace 1
stack trace 1
reading input: abc
should go in here
string is abc
line[i] is a
should not be empty
str is now abc
word is abc
adding use
starting to add abc
lineNum is 1
going here
added word abc
finished adding use
abc <--ok
abc <--ok
abc <--newline??
after-1 1
finished printing
pos is 4
abc
abc
abc
after-1 1
finished printing
should go in here
string is abc
line[i] is a
should not be empty
reading input:
should go in here
string is
line[i] is

ok so I'm starting over and combining some code I wrote before:

processLines.c (has main)

Code:

---

#include <stdio.h>
#include <ctype.h>
#include "table.h"
#define MAXLINELEN 100
#define MAXWORDLEN 20
FILE *input, *output;

int nextWord (char *, int, char *, int, struct table *p);
int getline(char s[], char l[], int max);
int getline2(char *, int max);
void processLine(char pline, char line);
int emptyLine (char line[]);

int main ( ) {
        char line[MAXLINELEN];
        char pline[MAXLINELEN];
        char word[MAXWORDLEN];
        int pos;

    input = fopen("table.test", "r");
        output = fopen("table.out", "w");


        struct table *p = newTable();
    int linecount = 1;
       
        while (getline (line, pline, MAXLINELEN-1)) {
        if (emptyLine(line) != -1) {
                  pos = 0;
          while (1) {
                if ((pos = nextWord (line, pos, word, linecount, p)) == -1) {
//here is where it loops and prints weird
                    printTable(p, output);
                    break;
                }
          }
          linecount++;
        }
    }
        printTable(p, output);
        fclose(input);
        fclose(output);
        return 0;
}

int emptyLine (char line[]) {
    int i=0;   
    while (1) {
         
          if (line[i] == '\0' || line[i] == '\n') {
            return -1;
          }
          else if (line[i] != ' ') {
              return i;
          }
          else {
              i++;
          }   
    }
}



int nextWord (char *str, int pos, char *word, int linecount, struct table *p) {

    int i=0;
    //fprintf(output, "pos is %d\n", pos);
    while (1) {
              if (*str == '\n' || *str == '\0' || *str == '#')
              return -1;
          else if (i == pos) {
                  break;
          }
              else {
                  i++;
                  str++;
          }
    }
    //fprintf(output, "str is now %s\n", str);
    int r = pos;

    char* word2 = word;
    int j;
    for (j=0; *str!='\n' || *str!=EOF; str++) {
            if (*str != ' ') {
                char c = *str;
                while (c != '\n' && c != ' ') {
                          r++;
                          *word = c;
                          word++;
                          str++;
                          c = *str;
            }
                *word = '\0';
               
                char last = *--word;
            if (last != ':') {
              addUse(word2, linecount, p);
              here is where I'm calling the functions from table.c
                  return r;
            }
            else {
                    addDef(word2, linecount, p);
            }
                //fprintf(output, "%s  %d\n", word2, linecount);
            break;
            }
            else {
                r++;
            j++;
            }
    }   
    word = word2;
    if (emptyLine(word) != -1)
      printf("%s\t%d\n", word, linecount);
    return r;
}

int getline(char s[], char l[], int lim) {

    int c, i=0;
    while (--lim>0 && (c=getc(input))!=EOF && c!='\n' && c!='#')
              s[i++] = c;
             
    if (c =='\n')
              s[i++] = c;
    else if (c == '#') {
        c=getc(input);
        while (c!='\n') {
              c=getc(input);
              s[i++] = '\n';
        }
    }
    s[i] = '\0';
   
    return i;
   
}

---

my table.c

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include "table.h"


struct lineNode {
  int lineoccur;
  struct lineNode *next;
};

/*struct entryNode {
        struct entryNode *next;
        struct entry *row;
};*/

struct entry {
      char * symbol;
      int linedef;
      struct lineNode *occur;
      struct entry *next;
};

struct table {
      int entrycount;
      struct entry *first;
};

        /* returns an empty table */
struct table * newTable( ) {
      struct table * table1 = malloc(sizeof(struct table));
      table1->first = NULL;
      table1->entrycount = 0;
      return table1;
}

struct entry *firstSymbol(struct table * symbols) {
        //printf("the symbol is %s\n", symbols->first->symbol);
        return symbols->first;
}


/* returns the result of adding a definition for the given symbol
  in the line with the given number to the table */
struct table * addDef (char * symbol, int lineNum, struct table * symbols){

        printf("should be abc is %s\n", symbols->first->symbol);
        printf("!!!adding %s\n", symbol);
        printf("should be abc is %s\n", symbols->first->symbol);

        struct entry *newEntry = malloc(sizeof(struct entry));
        newEntry->symbol = symbol;
        newEntry->linedef = lineNum;

        struct lineNode *o = malloc(sizeof(struct lineNode));
        o->lineoccur = -1;
        newEntry->occur = o;
        //struct entryNode *newEntryNode = malloc(sizeof(struct entryNode));
        //newEntryNode->row = newEntry;

        printf("still adding %s\n", symbol);

        if (symbols->entrycount == 0) {
                symbols->first = newEntry;
                symbols->entrycount = 1;
                printf("1added here %s\n", symbols->first->symbol);
                //printTable(symbols, "out");
        }
        else {
                struct entry *nEntry = symbols->first;
                while ( nEntry->next != NULL ) {
                        nEntry = nEntry->next;
                }
                nEntry->next = newEntry;
                (symbols->entrycount)++;
        }
        return symbols;
}


struct table * addUse (char * symbol, int lineNum, struct table * symbols) {

        printf("starting to add %s\n", symbol);
        //printf("lineNum is %d\n", lineNum);
        struct entry *nEntry = symbols->first;

        if (symbols->first == NULL) {
                //printf("going here\n");
                struct entry *newEntry = malloc(sizeof(struct entry));
                newEntry->symbol = symbol;
                newEntry->linedef = -1;
                struct lineNode *o = malloc(sizeof(struct lineNode));
                o->lineoccur = lineNum;
                newEntry->occur = o;
                symbols->first = newEntry;
                printf("added word!!!! %s\n", symbols->first->symbol);
                symbols->entrycount = 1;
                //printTable(symbols, "nothing");
        }
        else {
                while ( nEntry->symbol != symbol) {
                        if (nEntry->next == NULL) {
                                struct entry *newEntry = malloc(sizeof(struct entry));
                                newEntry->symbol = symbol;
                                newEntry->linedef = -1;
                                struct lineNode *o = malloc(sizeof(struct lineNode));
                                o->lineoccur = lineNum;
                                newEntry->occur = o;
                                nEntry->next = newEntry;
                                (symbols->entrycount)++;
                                break;
                        }
                        nEntry = nEntry->next;
                }
                struct lineNode *o = nEntry->occur;
                while ( (o->next != NULL) && (o->lineoccur != -1) ) {
                        o = o->next;
                }

                if (o->lineoccur == -1) {
                        o->lineoccur = lineNum;
                }
                else {
                        struct lineNode *newLineNode = malloc(sizeof(struct lineNode));
                        newLineNode->lineoccur = lineNum;
                        newLineNode->next = NULL;
                        o->next = newLineNode;
                }

        }
        printf("finished adding use %s\n", symbols->first->symbol);
        return symbols;
}

void processSymbol (char * symbol) {
        char* word2 = symbol;

        while (1) {
                if (*symbol == '\n' || *symbol == ' ') {
                        *symbol = '\0';
                        symbol = word2;
                        break;
                }
                else {
                        symbol++;
                }
        }
        printf("processed %s\n", symbol);
}

        /* print the table, in the format described above, to the given file */
void printTable (struct table * symbols, FILE * out) {
    struct entry *n = symbols->first;
    printf("FIRST IS %s\n", symbols->first->symbol);
    //printf("%s", n->symbol);

        while (n != NULL) {
                //processSymbol(n->symbol);
            printf("%s\t", n->symbol);
            //printf("after");
            printf("%d\t", n->linedef);

            struct lineNode *nline = n->occur;

            while ((nline != NULL) && (nline->lineoccur != -1)) {
                    printf("%d\t", nline->lineoccur);
                    nline = nline->next;
            }
            printf("\n");

            fprintf(out, "%s\t", n->symbol);
            fprintf(out, "%d\t\n", n->linedef);
            n = n->next;
    }

        printf("finished printing \n");
}

---

starting to add abc
added word!!!! abc
finished adding use abc
FIRST IS abc <-- I added "abc" to the table
abc -1 1 <-- table is fine with one entry
finished printing
should be abc is y: <--this should have been the first, "abc", as called from addDef
!!!adding y:
should be abc is y:
still adding y:
y: 2
FIRST IS y:
y: -1 1
y: 2
finished printing
should be abc is abc:
!!!adding abc:
should be abc is abc:
still adding abc:
abc: 3
FIRST IS abc:
abc: -1 1
abc: 2
abc: 3
finished printing
starting to add y
finished adding use y
FIRST IS y
y -1 1 4
y 2
y 3
finished printing
starting to add y
finished adding use y
FIRST IS y
y -1 1 4 5
y 2
y 3
finished printing
FIRST IS y
y -1 1 4 5
y 2
y 3
finished printing

why are my symbols getting replaced? when I just call the functions in table.c without reading from an input file, it adds and prints fine.

Quote:

---

Originally Posted by BEN10

Isn't it that the when the program has executed properly, the allocated memory is automatically freed and can be used somewhere else?

---

honestly, i am not positive. i really thought it would stay reserved and thus wasted until OS reboot or until some other process the OS does to "clean up" memory at a later time, i.e. not immediately after the program executes--whether successful or not. i havent looked into those technical details in a number of years so maybe things are "better" now. edit: but i highly doubt it.

i saw something like 8 'malloc' calls, and still no 'free' calls. are you reading what im saying? fix your memory leaks.

Quote:

---

Originally Posted by coni

why are my symbols getting replaced? when I just call the functions in table.c without reading from an input file, it adds and prints fine.

---

if this is true, then the only reason is that youre reading the input file incorrectly. i havent read all of your code again so i dont really remember it, but say your input file is this:

Quote:

---

Originally Posted by input.txt

abc
def
123
456

---

then in your program, for every read you do, print out what value it was, surrounded by quotes. surrounding it by quotes makes it obvious as to the "boundaries" of the value. if you dont have quotes (or whatever delimiter) then you may not notice a leading/trailing space/newline or other characters you dont expect. output after reading each value would be something like:

Code:

---

line #1 from file: 'abc'

---

i see you have some output, but i can assume you arent doing this (printing out the values read from the file). because if you were, you would have also given us the contents of the file you were reading, so we can also verify it.

again, this is assuming your code is correct, as you say, and that its just a problem with reading values from file.

ok so I have mostly everything fixed now. I realized that I had been reusing the same char array and setting pointers to it, so it changed when I read in the next word. To fix that I used a strcopy instead. But when I print everything out, the first few times seem ok, and then I encounter a segfault

main()

Code:

---

int main ( ) {
        char line[MAXLINELEN];
        char pline[MAXLINELEN];
        char word[MAXWORDLEN];
        int pos;

    input = fopen("table.test", "r");
        output = fopen("table.out", "w");


        struct table *p = newTable();
    int linecount = 1;

    //addUse("aaabc", 1, p);
    //addDef("yyyy:", 2, p);
       
        while (getline (line, pline, MAXLINELEN-1)) {
        //if (emptyLine(line) != -1) {
                  pos = 0;
          while (1) {
                if ((pos = nextWord (line, pos, word, linecount, p)) == -1) {
                        break;
                }
                printTable(p, output);
                //this prints fine but eventually reaches a segfault
          }
          linecount++;

    }
    printTable(p, output);
    if I take out the looping printTable and only keep this one it doesn't print, only segfaults
      fclose(input);
        fclose(output);
        return 0;
}

---

printTable in table.c

Code:

---

void printTable (struct table * symbols, FILE * out) {
    struct entry *n = symbols->first;
//this line is causing the segfault

        while (n != NULL) {
            printf("%s\t", n->symbol);
            printf("%d\t", n->linedef);
            fprintf(out, "%s\t", n->symbol);
            fprintf(out, "%d\t", n->linedef);

            struct lineNode *nline = n->occur;

            while ((nline != NULL) && (nline->lineoccur != -1)) {
                    printf("%d\t", nline->lineoccur);
                    fprintf(out, "%d\t", nline->lineoccur);
                    nline = nline->next;
            }
            printf("\n");
            fprintf(out, "\n");


            n = n->next;
    }
        printf("finished printing \n");
}

---

nextWord that main() calls

Code:

---

int nextWord (char *str, int pos, char *word, int linecount, struct table *p) {

        if (emptyLine(str) == -1) {
                return -1;
        }
    int i=0;
    while (1) {
              if (*str == '\n' || *str == '\0' || *str == '#')
              return -1;
          else if (i == pos) {
                  break;
          }
              else {
                  i++;
                  str++;
          }
    }
    int r = pos;

    if (emptyLine(str) == -1)
            return -1;

    char* word2 = word;
    int j;
    for (j=0; *str!='\n' || *str!=EOF; str++) {
            if (*str >= 33 && *str <= 126) {
                char c = *str;
                //firstSymbol(p);
                while (c != '\n' && c != ' ') {
                          r++;
                          *word = c;
                          word++;
                          str++;
                          c = *str;
            }
                *word = '\0';
                char last = *--word;
          if (last == ':') {
                  *word = '\0'; //takes out the ':' character

I'm using strcpy here so why would it print out find and then the p->first point again to null?
                  char * newString = malloc(sizeof(strlen(word2)));
                  strcpy(newString, word2);
                  addDef(newString, linecount, p);
            }
          else {
                  char * newString = malloc(sizeof(strlen(word2)));
                  strcpy(newString, word2);
                  addUse(newString, linecount, p);
                  return r;
            }
            break;
            }
            else {
                r++;
            j++;
            }
    }   
    word = word2;

    return r;
}

---

- it seems you have a lot of pointer arithmetic and looping which is huge potential for logic errors such as those your experiencing with the dynamic memory. i would review those algorithms/loops and trace it on paper. if you trace a single, just one, runthrough of your program, with adding just one or maybe two elements to your table, you will solve it. this is somewhat tedious, however it is very common to do (i.e. in algorithms courses and in general debugging) and it is a near-guaranteed way of solving your problem, down to the exact line. (i say near-guaranteed because it may be some external thing, such as OS, disk space, permissions, etc, that cant be verified with your code on paper).

- you still do not have "free" calls, who knows, maybe your program is fine but due to all of the memory leaks its breaking something? fix this. otherwise i will stop donating my time giving you suggestions if you dont implement or even at least comment on them saying your not going to implement them for whatever reason.

- you didnt post your "addUse" and "addDef" functions with your latest updated code (could the problem be in there?)

- have you verified there is no logic error in your file IO? you should strip your code down to the minimum possible (file IO shouldnt be required to test your code, just use std/console IO), to reduce complexity and to minimize introducing problems. i.e., does the program run fine with STD IO and no calls to "printTable"? try and partition the problem like this.

anyways, it seems you do some code, run into a problem, post here, get input or a solution and implement it (or not even implement it), and go on to adding more functionality/code. you should verify that your initial problem (whatever that even was, i dont remember) is indeed fixed. that is, go back to that initial "fixed" code here, and test it with adding 0, 1, 5, 100, 1000+ entries (though you may run out of memory due to all of your memory leaks). test it with weird input strings and numbers. then move on to working with files, or printing it, or whatever it is your trying to do. when you test an algorithm/program with one set of input, it means nothing. only when you test it with "sufficiently large" variety of inputs can you gain some confidence that it "works".