C Program - warning: assignment makes pointer from integer without a cast - c

Question

I'm trying to read a file and store its content in a variable, here's my code:
#define _BSD_SOURCE
#include <stdio.h>
#include <sys/stat.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
// CEK ROUTER MODEL
char* router_model;
char* model() {
char filename[] = "/tmp/cpuinfo";
char* key = "system type";
char* value;
FILE *file = fopen(filename, "r");
if (file != NULL) {
char line[1000];
while (fgets(line, sizeof line, file) != NULL) /* read a line from a file */ {
//fprintf(stdout, "%s", line); //print the file contents on stdout.
if (strncmp(line, key, strlen(key)) == 0) {
char* value = strchr(line, ':');
value += 2;
router_model = strdup(value);
break; // once the key has been found we can stop reading
}
}
fclose(file);
}
else {
perror(filename); //print the error message on stderr.
}
return router_model;
}
// TULIS SERIAL NUMBER KE FILE
char tulis(char p[100]) {
// Write a serial number to a file
char sn[30];
char encrypt_sn[300];
printf("Serial Number:\n");
scanf("%s", sn);
FILE *f = fopen("/tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c", "w");
if (f == NULL) {
printf("Error opening file!\n");
exit(1);
}
fprintf(f,"Serial Number: %s", sn);
fclose(f);
sprintf(encrypt_sn, "ccrypt -e /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c -K %s", p);
system(encrypt_sn);
system("mv /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c");
printf("Serial number is saved in /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c\n");
return 0;
}
// BACA SERIAL NUMBER & SIMPAN DALAM SEBUAH VARIABLE
char baca(char p[100]) {
// Store the serial number from a file in a variable
char line[50];
char decrypt_sn[300];
char key[30] = "Serial Number";
char *serial_number;
if( access( "/tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c", F_OK ) != -1 ) {
system("cp /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c /tmp/");
system("mv /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt");
sprintf(decrypt_sn, "ccrypt -d /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt -K %s", p);
system(decrypt_sn);
FILE *file = fopen("/tmp/fsn-55cfc8770b69cc07268fae7f25ee444c", "r");
if (file == NULL) {
printf("Error opening file!\n");
exit(1);
}
while (fgets(line, sizeof line, file) != NULL) /* read a line from a file */ {
//fprintf(stdout, "%s", line); //print the file contents on stdout.
if (strncmp(line, key, strlen(key)) == 0) {
char* value = strchr(line, ':');
value += 2;
serial_number = strdup(value);
break; // once the key has been found we can stop reading
}
}
fclose(file);
//printf("Your hardware serial number is: (%s)\n", serial_number);
remove("/tmp/fsn-55cfc8770b69cc07268fae7f25ee444c");
}
else {
printf("fsn not found\n");
return -1;
}
return 0;
}
int main(int argc, char* argv[]) {
char *r;
char *del;
char *decrypt;
int ret;
char input[30];
char *p;
char *original_sn;
p = "MmI4MTUxM2FjMjRlMDkzYmRkZGQyMjcwMjQ4OWY3MDAwNGZiYTM0MWNkZGIxNTdlYzAxN2";
//tulis(p);
original_sn = baca(p);
printf("SN: %s\n", original_sn);
return 0;
}
The file is /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c and the content of that file is Serial Number: 1866203214226041 and original_sn should output 1866203214226041. However when I run that code I get:
test.c: In function ‘main’:
test.c:105:14: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
original_sn = baca(p);
^
SN: (null)
How do I fix it ?

Answer 1

This happens because your baca function returns a char, whereas you are assigning its return value to a char *. Maybe you wanted to use a char variable.

Answer 2

If function baca can change the contents of the memory block pointed by the input argument:
Change this:
char* p = "MmI4MTUxM2FjMjRlMDkzYmRkZGQyMjcwMjQ4OWY3MDAwNGZiYTM0MWNkZGIxNTdlYzAxN2";
To this:
char p[] = "MmI4MTUxM2FjMjRlMDkzYmRkZGQyMjcwMjQ4OWY3MDAwNGZiYTM0MWNkZGIxNTdlYzAxN2";
If function baca cannot change the contents of the memory block pointed by the input argument:
Change this:
char baca(char p[])
To this:
char baca(const char* p)

Answer 3

In baca you are allocating initialised memory using strdup:
serial_number = strdup(value);
, then you do nothing with that.
It is clear that you think that the function returns a pointer to that memory so you can print it's content. However, it is not what you are doing. Because all your baca function is doing is returning a value indecating if it sucseede (0) or not (-1). And you are jut ignoring that pointer and leaving some wasted unused memory allocated by your prog.
Their are 2 methodes to fix your code:
Method1 : returning the serial_number
char* baca(const char* p) {
// Store the serial number from a file in a variable
char line[50];
char decrypt_sn[300];
char key[30] = "Serial Number";
char *serial_number=NULL;
if( access( "/tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c", F_OK ) != -1 ) {
system("cp /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c /tmp/");
system("mv /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt");
sprintf(decrypt_sn, "ccrypt -d /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt -K %s", p);
system(decrypt_sn);
FILE *file = fopen("/tmp/fsn-55cfc8770b69cc07268fae7f25ee444c", "r");
if (file == NULL) {
printf("Error opening file!\n");
exit(1);
}
while (fgets(line, sizeof line, file) != NULL) /* read a line from a file */ {
//fprintf(stdout, "%s", line); //print the file contents on stdout.
if (strncmp(line, key, strlen(key)) == 0) {
char* value = strchr(line, ':');
if(value!=NULL){/*testing the return value for erros so you prog doesn't cruch*/
value += 2;
serial_number = strdup(value);
}
/*in case off erreor you can choose one of two options:*/
/*optinon1: print an error mesage then kill your prog*/
else{
printf("Error: corrupted file!\n");
exit(1);
}
/*option 2: removing the else part your baca then will return NULL and the calling code should understand that an error has occured*/
break;
}
}
fclose(file);
remove("/tmp/fsn-55cfc8770b69cc07268fae7f25ee444c");
}
else {
printf("fsn not found\n");
}
return serial_number;
}
int main(int argc, char* argv[]) {
char *r;
char *del;
char *decrypt;
int ret;
char input[30];
char *p;
char *original_sn;
p = "MmI4MTUxM2FjMjRlMDkzYmRkZGQyMjcwMjQ4OWY3MDAwNGZiYTM0MWNkZGIxNTdlYzAxN2";
//tulis(p);
original_sn = baca(p);
if(original_sn!=NULL){
printf("SN: %s\n", original_sn);
free(original_sn);/*you should free the memory allocated by strdup once you are done using it.*/
}
else{
printf("An error has occured\n");
}
return 0;
}
Method2 : pass by reference
char baca(const char* p, char **serial_number) {
// Store the serial number from a file in a variable
char line[50];
char decrypt_sn[300];
char key[30] = "Serial Number";
char ret = 0;/*the return value 0 means no error.*/
if( access( "/tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c", F_OK ) != -1 ) {
system("cp /tmp/halo/fsn-55cfc8770b69cc07268fae7f25ee444c /tmp/");
system("mv /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt");
sprintf(decrypt_sn, "ccrypt -d /tmp/fsn-55cfc8770b69cc07268fae7f25ee444c.cpt -K %s", p);
system(decrypt_sn);
FILE *file = fopen("/tmp/fsn-55cfc8770b69cc07268fae7f25ee444c", "r");
if (file == NULL) {
printf("Error opening file!\n");
exit(1);
}
while (fgets(line, sizeof line, file) != NULL) /* read a line from a file */ {
//fprintf(stdout, "%s", line); //print the file contents on stdout.
if (strncmp(line, key, strlen(key)) == 0) {
char* value = strchr(line, ':');
if(value!=NULL){/*testing the return value for erros so you prog doesn't cruch*/
value += 2;
*serial_number = strdup(value);
}
/*in case off erreor you can choose one of two options:*/
else{
/*optinon1: print an error mesage then kill your prog*/
/*option 2: making the return value non 0 and the calling code should understand that an error has occured*/
#define OPTION1
#ifdef OPTION1
printf("Error: corrupted file!\n");
exit(1);
#else
ret=-2; //to used this option comment out #define OPTION1
#endif
}
break;
}
}
fclose(file);
remove("/tmp/fsn-55cfc8770b69cc07268fae7f25ee444c");
}
else {
printf("fsn not found\n");
ret=-1;
}
return ret;
}
int main(int argc, char* argv[]) {
char *r;
char *del;
char *decrypt;
int ret;
char input[30];
char *p;
char *original_sn=NULL;
p = "MmI4MTUxM2FjMjRlMDkzYmRkZGQyMjcwMjQ4OWY3MDAwNGZiYTM0MWNkZGIxNTdlYzAxN2";
//tulis(p);
switch(baca(p,&original_sn))
{
case 0: //evrything is fine
printf("SN: %s\n", original_sn);
free(original_sn);
break;
case -1:/* handle each error as you should*/
case -2:
default:
printf("An error has occured\n");
}
return 0;
}
Hope this helps. :).