Segmentation Fault fgets() two pass assembler [closed] - c

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#include<string.h>
typedef struct{
char Mnemonic[7];
int code;
} code;
typedef struct{
char label[10];
unsigned int location;
} symbolTab;
int opLook(char * mnemonic, code * optable)
{
int i = 0;
int value = 0;
for(i ; i<25 ; i++)
{
if(strcmp(mnemonic, optable[i].Mnemonic) == 0)
{
value = optable[i].code;
return value;
}
}
return value;
}
int opValid(char * mnemonic, code * optable)
{
int i = 0;
for(i ; i<25 ; i++)
{
if(strcmp(mnemonic, optable[i].Mnemonic) == 0)
{
return 1;
}
}
return 0;
}
int labelcheck(char * label, symbolTab * Table, int counter)
{
int i = 0;
int flag = 0;
if (counter == 0)
{
return flag;
}
else
{
for(i; i <counter; i ++)
{
if(strcmp(label, Table[i].label) == 0)
{
flag = 1;
}
}
return flag;
}
}
unsigned int labelVal(char * label, symbolTab * Table, int counter)
{
int i = 0;
for(i; i <counter; i ++)
{
if(strcmp(label, Table[i].label) == 0)
{
return Table[i].location;
}
}
}
void Assemble(char* filename)
{
unsigned int locctr = 0; /*location counter*/
unsigned int prolen = 0; /*program length*/
int mnemoVal; /*mnemonic Value in Int*/
int labelctr = 0;
code Opta[25] = {{"ADD", 24},{"AND",88},{"COMP",40},{"DIV",36},{"J",60},
{"JEQ",48},{"JGT",52},{"JLT",56},{"JSUB",72},{"LDA",00},
{"LDCH",80},{"LDL", 8},{"LDX", 4},{"MUL",32},{"OR",68},
{"RD",216},{"RSUB",76},{"STA",12},{"STCH",84},{"STL",20},
{"STX",16},{"SUB",28},{"TD",224},{"TIX",44},{"WD",220}};
symbolTab symTab[500];
char buffer[255];
FILE * source;
FILE * interFile;
FILE * objF;
FILE * ListFile;
interFile = fopen("intermidiateFile.txt", "w+");
ListFile = fopen("ListingFile.txt", "w+");
objF = fopen("ObjectFile.txt", "w+");
source = fopen("source.txt", "r");
char * lab; /*label*/
char * mnemo; /*mnemonic*/
char * operand;
char * address = "adress";
unsigned int opeaddress;
fgets(buffer, 255, source);
if (buffer[0] != '.')
{
fprintf(interFile, "%s", buffer);
}
/*Getting first line and initialization of Location Counter*/
if(buffer[0] == '.') /* if the line is a comment continue with the next iteration of the loop*/
{
locctr = 0;
}
else
{
if(buffer[0] == ' ' || buffer[0] == '\t')
{
mnemo = strtok(buffer, " \t");
operand = strtok(NULL, " \t");
if(strcmp(mnemo, "START") == 0)
{
locctr = strtol(operand, NULL, 16);
}
else
{
/*error*/
}
}
else
{
lab =strtok(buffer, " \t");
mnemo = strtok(NULL, " \t");
operand = strtok(NULL, " \t");
if(strcmp(mnemo, "START") == 0)
{
locctr = strtol(operand, NULL, 16);
}
else
{
/*error*/
}
}
}
/* End of the location counter initialization */
/*start while loop*/
while(!feof(source))
{
memset(lab, '\0', strlen(lab));
memset(mnemo, '\0', strlen(mnemo));
memset(operand, '\0', strlen(operand));
fgets(buffer, 255, source);
fprintf(interFile, "%s", buffer);
if(buffer[0] == '.') /* if the line is a comment continue with the next iteration of the loop*/
{
continue;
}
else /* Else for... If it is not a comment, then check if it start with a character or a space*/
{
if(buffer[0] == ' ' || buffer[0] == '\t') /* If it start with a space, then it is just a mnemonic or mnemonic & operand*/
{
mnemo = strtok(buffer, " \t\n\r");
if (strcmp(mnemo, "END") == 0)
{
break;
}
if(strcmp(mnemo, "RSUB") == 0)
{
mnemoVal = opLook(mnemo, Opta);
fprintf(interFile, "%x %02x\n", locctr, mnemoVal);
}
else
{
operand = strtok(NULL, " \t\r\n");
mnemoVal = opLook(mnemo, Opta);
fprintf(interFile, "%x %02x %s\n", locctr, mnemoVal, operand);
}
}
else
{
lab = strtok(buffer, " \t\n\r"); /* it has a label, mnemonic and operand*/
if(labelcheck(lab, symTab, labelctr) == 0) /* check if the label is already in the symTab, if not, add it, otherwise it is an error*/
{
strcpy(symTab[labelctr].label, lab);
symTab[labelctr].location = locctr;
labelctr++;
mnemo = strtok(NULL, " \t\n\r");
if (strcmp(mnemo, "END") == 0)
{
break;
}
operand = strtok(NULL, " \t\n\r");
mnemoVal = opLook(mnemo, Opta);
}
else
{
mnemo = strtok(NULL, " \t\n\r");
if (strcmp(mnemo, "END") == 0)
{
break;
}
operand = strtok(NULL, " \t\n\r");
mnemoVal = opLook(mnemo, Opta);
}
fprintf(interFile, "%x %s %02x %s\n", locctr, lab, mnemoVal, operand);
}
}
if(strcmp(mnemo, "WORD") == 0 )
{
locctr = locctr + 3;
}
else if(strcmp(mnemo, "BYTE") == 0 )
{
unsigned int val;
if (operand[0] =='C')
{
val = strlen(operand) - 3;
locctr = locctr + val;
}
else
{
val = (strlen(operand) - 3)/2;
locctr = locctr + val;
}
}
else if(strcmp(mnemo, "RESB") == 0)
{
locctr = locctr + atoi(operand);
}
else if(strcmp(mnemo, "RESW") == 0)
{
locctr = locctr + (3*atoi(operand));
}
else
{
locctr= locctr + 3;
}
}
/* End of While loop*/
prolen = locctr - symTab[0].location;
fprintf(interFile, "\n%x", prolen);
fclose(source);
fclose(interFile);
interFile = fopen("intermidiateFile.txt", "r");
/*Start the Listing File and Object File ---------------------Pass 2----------- */
fgets(buffer, 255, interFile);
if(buffer[0] == '.') /* if the line is a comment continue with the next iteration of the loop*/
{
locctr = 0;
/*Error missung Start or Misplaced*/
}
else
{
if(buffer[0] == ' ' || buffer[0] == '\t')
{
mnemo = strtok(buffer, " \t");
operand = strtok(NULL, " \t");
if(strcmp(mnemo, "START") == 0)
{
locctr = strtol(operand, NULL, 16);
strcpy(address, operand);
fprintf(ListFile, "%X %s %s\n", locctr, mnemo, operand);
}
else
{
/*error*/
}
}
else
{
lab =strtok(buffer, " \t");
mnemo = strtok(NULL, " \t");
operand = strtok(NULL, " \t");
if(strcmp(mnemo, "START") == 0)
{
locctr = strtol(operand, NULL, 16);
fprintf(ListFile, "%x %s %s %s\n", locctr, lab, mnemo, operand);
fprintf(objF, "H%s__%06x%06x\n", lab, locctr, prolen);
}
else
{
/*error*/
}
}
}
while(!feof(interFile))
{
memset(lab, '\0', strlen(lab));
memset(mnemo, '\0', strlen(mnemo));
memset(operand, '\0', strlen(operand));
memset(address, '\0', strlen(address));
memset(buffer, '\0', strlen(buffer));
fgets(buffer, 255, interFile);
if (buffer[0] == '\r')
{
continue;
}
if(buffer[0] == ' ' || buffer[0] == '\t')
{
mnemo = strtok(buffer, " \t\n\r");
if (strcmp(mnemo, "END") == 0)
{
break;
}
if(strcmp(mnemo, "RSUB") == 0)
{
memset(buffer, '\0', strlen(buffer));
fgets(address, 255, interFile);
mnemoVal = opLook(mnemo, Opta);
fprintf(ListFile, "%s %s %X0000", address, mnemo, mnemoVal);
}
else
{
operand = strtok(NULL, " \t\r\n");
mnemoVal = opLook(mnemo, Opta);
memset(buffer, '\0', strlen(buffer));
fgets(address, 255, interFile);
if (labelcheck(operand, symTab, labelctr) == 1)
{
opeaddress = labelVal(operand, symTab, labelctr);
}
else
{
opeaddress = 0;
/* error*/
}
fprintf(ListFile, "%s %s %s %02X%04X", address, mnemo, operand, mnemoVal, opeaddress);
}
}
else if (buffer[0] == '.')
{
fprintf(ListFile, "%s\n", buffer);
}
else
{
lab = strtok(buffer, " \t\n\r");
mnemo = strtok(NULL, " \t\n\r");
operand = strtok(NULL, " \t\n\r");
mnemoVal = opLook(mnemo, Opta);
memset(buffer, '\0', strlen(buffer));
fgets(address, 255, interFile);
if (labelcheck(operand, symTab, labelctr) == 1)
{
opeaddress = labelVal(operand, symTab, labelctr);
}
else
{
opeaddress = 0;
/* error*/
}
fprintf(ListFile, "%s %s %s %s %02X%04X", address, lab, mnemo, operand, mnemoVal, opeaddress);
}
}
fclose(interFile);
fclose(objF);
fclose(ListFile);
}
The error occurs in the last while loop when executing fgets();
I have looked if I had any variable or syntax wrong, but everything looks fine.
This is a part of a two pass assemble. The error varies between the fgets in the last while loop. At first I thought that it was the memset function, but the error still happened when I mark them as comments

Answer 1

Because of
char * address = "adress";
address is pointing to Read Only Memory
Trying to modify string literals (in your case "adress") invokes undefined behavior.
Then in your last loop
strcpy(address, operand);
memset(address, '\0', strlen(address));
fgets(address, 255, interFile);
Are wrong.
You could change that variable to a simple array of chars with enough room for your needs, e.g.:
char address[128];