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Segmentation fault... Posted by IDK on 5 Jun 2006 at 11:30 AM

I have a segmentation fault again...
It's a little wierd...
This is some piece of code I'm working on:

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

char look;             // { Lookahead Character }
FILE *ifile;           // input stream
FILE *ofile;           // output stream
char **KWlist;

//{--------------------------------------------------------------}
//{ Read New Character From Input Stream }

void GetChar(){
   look = fgetc(ifile);
}

//{--------------------------------------------------------------}
//{ Report Error}

void Abort(char* s){
   printf("\nError %s.", s);
   abort();
}

void Expected(char* s){
   printf("Error: %s Expected\n", s);
   abort();
}

//{--------------------------------------------------------------}
//{ Match a Specific Input Character }

void match(char x){
   if(look == x)
       GetChar();
   else{
       char* c = " \n";
       c[0] = x;
       Expected(c);
   }
}

//{--------------------------------------------------------------}
//{ Recognicion funcs }
char upcase(char c){
     if((c >= 'a') & (c <= 'z'))
         c += 'A' - 'a';
     return c;
}

int IsAlpha(char c){
   c = upcase(c);
   return ((c >= 'A') & (c <= 'Z'));
}

int IsDigit(char c){
    return ((c >= '0') & (c <= '9'));
}

int IsOp(char c){
    return (c == '+') | (c == '-') | (c == '*') | (c == '/') | (c == '<') | (c == '>') | (c == ':') | (c == '=') | (c == '!');
}

int IsAlNum(char c){
    return IsAlpha(c) | IsDigit(c);
}

int IsWhite(char c){
    return (c == ' ') | (c == '\t') | (c == '\n');
}


//{--------------------------------------------------------------}
//{ Get an Identifier }

void skipWhite(){
    while(IsWhite(look))
        GetChar();
}

void Fin(){
    if(look == '\n') GetChar();
    if(look == '\r') GetChar();
}

int Lookup(char ** list, char* s, int n){
    //++n;
    while(n--)
        if(list[n][0] == s[0])
            if(strcmp(list[n], s) == 0)
                return 1;
    return 0;
}


char* getName(){
    char *c, *p;
    if ((c=(char *) malloc(9))==NULL) return NULL;
    p = c;
    if(!IsAlpha(upcase(look))) Expected("Name");

    while(IsAlNum(look)){
        *p = upcase(look);
        ++p;
        GetChar();
    }
    *p = 0;
    skipWhite();
    return c;
}

char* getNum(){
    char *c, *p;
    if ((c=(char *) malloc(17))==NULL) return NULL;
    p = c;
    if(!IsDigit(look)) Expected("Integer");
    while(IsDigit(look)){
        *p = upcase(look);
        ++p;
        GetChar();
    }
    *p = 0;
    skipWhite();
    return c;
}

char* getOp(){
    char *c, *p;
    if ((c=(char *) malloc(4))==NULL) return NULL;
    p = c;
    if(!IsOp(look)) Expected("Integer");
    while(IsOp(look)){
        *p = upcase(look);
        ++p;
        GetChar();
    }
    *p = 0;
    skipWhite();
    return c;
}

char* scan(){ //remember to free!!
    skipWhite();
    char *c;
    while(look == '\n')
        Fin();

    if(IsAlpha(look))
        c = getName();
    else if(IsDigit(look))
        c = getNum();
    else if(IsOp(look))
        c = getOp();
    else {
        if ((c=(char *) malloc(2))==NULL) return NULL;
        *c = look;
        ++c;
        *c = 0;
        --c;
        GetChar();
    }
    return c;
}


//{--------------------------------------------------------------}
//{ Initialize }

void init(){
    ifile = stdin;  //fopen("test.q", "r");
    ofile = stdout;
    GetChar();

    if ((KWlist=(char **) malloc(6))==NULL) Abort("malloc error");
    KWlist[0] = "IF";
    KWlist[1] = "ELSE";
    KWlist[2] = "END";
    KWlist[3] = "ENDIF";
    KWlist[4] = "1234";
}


//{--------------------------------------------------------------}
//{ Main Program }

int main(){
    init();

    char* c;
    //scanf("%s",c); //this line works
    c = scan();      //but this doesn't
    printf("%s\n", c);
    printf("%d\n", Lookup(KWlist, c, 4)); //if I put a three here it works but not if it's a four and scan() is used.

    free(c);
    free(KWlist);

    return 0;
}

Read the comments in main to understand the prob...
The problem should be with scan() but I can't see why.

It only occures when the third parameter in Lookup is 4 and scan() is used. When the parameters is lower, or scanf() is used it works.

Happy coding wishes
the one and only
Niklas Ulvinge aka IDK

C and C++

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