Xotira xavfsizligi va nosozliklarni tuzatish

gcc -std=c17 -g -fsanitize=address,undefined dastur.c -o dastur
./dastur

#include <stdio.h>

int main(void) {
    int ballar[5] = {85, 92, 78, 95, 88};

    printf("%d\n", ballar[10]);      /* chegaradan tashqarida */

    return 0;
}

=================================================================
ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffd...
READ of size 4 at 0x7ffd... thread T0
    #0 0x... in main dastur.c:6
Address is located in stack of thread T0 at offset 48 in frame
    #0 0x... in main dastur.c:3
  This frame has 1 object(s):
    [32, 52) 'ballar' (line 4) <== Memory access at offset 48 overflows

#include <stdlib.h>

int main(void) {
    int *massiv = malloc(100 * sizeof(int));
    massiv[0] = 42;

    return 0;      /* free chaqirilmadi */
}

=================================================================
ERROR: LeakSanitizer: detected memory leaks

Direct leak of 400 byte(s) in 1 object(s) allocated from:
    #0 0x... in malloc
    #1 0x... in main dastur.c:4

#include <stdlib.h>

int main(void) {
    int *massiv = malloc(10 * sizeof(int));

    free(massiv);
    massiv[0] = 42;      /* ozod qilingandan keyin */

    return 0;
}

ERROR: AddressSanitizer: heap-use-after-free on address 0x...
WRITE of size 4 at 0x... thread T0
    #0 0x... in main dastur.c:7
freed by thread T0 here:
    #1 0x... in main dastur.c:6

gcc -std=c17 -g dastur.c -o dastur
valgrind --leak-check=full --show-leak-kinds=all ./dastur

==12345== HEAP SUMMARY:
==12345==     in use at exit: 400 bytes in 1 blocks
==12345==   total heap usage: 1 allocs, 0 frees, 400 bytes allocated
==12345==
==12345== 400 bytes in 1 blocks are definitely lost in loss record 1 of 1
==12345==    at 0x4C2FB0F: malloc (vg_replace_malloc.c:299)
==12345==    by 0x108668: main (dastur.c:4)
==12345==
==12345== LEAK SUMMARY:
==12345==    definitely lost: 400 bytes in 1 blocks

gcc -std=c17 -g dastur.c -o dastur
gdb ./dastur

$ gdb ./dastur
(gdb) break 12
Breakpoint 1 at 0x1169: file dastur.c, line 12.

(gdb) run
Breakpoint 1, main () at dastur.c:12
12          int natija = bol(a, b);

(gdb) print a
$1 = 10

(gdb) print b
$2 = 0

(gdb) next
Program received signal SIGFPE, Arithmetic exception.

(gdb) backtrace
#0  bol (a=10, b=0) at dastur.c:5
#1  main () at dastur.c:12

gcc -std=c17 -Wall -Wextra -Wpedantic -Wshadow -Wconversion dastur.c -o dastur

int massiv[5];

for (int i = 0; i <= 5; i++) {    /* XATO: <= */
    massiv[i] = 0;                /* massiv[5] mavjud emas */
}

if (holat = 1) { ... }            /* qiymat berdi, taqqoslamadi */

for (int i = 0; i < 10; i++);     /* sikl bo'sh */
{
    printf("%d\n", i);            /* faqat bir marta */
}

char bufer[10];
strcpy(bufer, "Bu matn juda uzun");    /* bufer to'lib ketdi */

double narx = 99.5;
printf("%d\n", narx);             /* XATO: %f bo'lishi kerak */

char *salomlash(void) {
    char xabar[50] = "Salom";
    return xabar;                 /* funksiya tugagach yo'q bo'ladi */
}

/* 1. Dinamik xotira */
char *salomlash(void) {
    char *xabar = malloc(50);
    if (xabar != NULL) strcpy(xabar, "Salom");
    return xabar;                 /* chaqiruvchi free qiladi */
}

/* 2. Buferni chaqiruvchi bersin - eng yaxshi usul */
void salomlash(char *bufer, size_t hajm) {
    snprintf(bufer, hajm, "Salom");
}

/* 3. static (ehtiyot bo'ling: bitta nusxa, ko'p oqimda xavfli) */
const char *salomlash(void) {
    static char xabar[50] = "Salom";
    return xabar;
}

double ortacha = yigindi / soni;              /* butun bo'lish! */
double togri = (double) yigindi / soni;       /* to'g'ri */

#include <stdio.h>

int main(void) {
    char toliq[20];
    const char *ism = "Husanboy";
    const char *familiya = "Qodirov";

    int yozildi = snprintf(toliq, sizeof(toliq), "%s %s", ism, familiya);

    printf("Natija    : %s\n", toliq);
    printf("Kerak edi : %d belgi\n", yozildi);

    if (yozildi >= (int) sizeof(toliq)) {
        printf("Ogohlantirish: matn kesildi!\n");
    }

    return 0;
}

#include <stdio.h>

typedef enum {
    XATO_YOQ = 0,
    XATO_NOTOGRI_ARGUMENT,
    XATO_NOLGA_BOLISH,
    XATO_XOTIRA
} Xato;

const char *xato_matni(Xato x) {
    switch (x) {
        case XATO_YOQ:               return "Xato yo'q";
        case XATO_NOTOGRI_ARGUMENT:  return "Noto'g'ri argument";
        case XATO_NOLGA_BOLISH:      return "Nolga bo'lish";
        case XATO_XOTIRA:            return "Xotira yetmadi";
        default:                     return "Noma'lum xato";
    }
}

Xato bol(int a, int b, int *natija) {
    if (natija == NULL) {
        return XATO_NOTOGRI_ARGUMENT;
    }

    if (b == 0) {
        return XATO_NOLGA_BOLISH;
    }

    *natija = a / b;
    return XATO_YOQ;
}

int main(void) {
    int natija;

    Xato x = bol(17, 5, &natija);
    printf("17 / 5: %s", xato_matni(x));
    if (x == XATO_YOQ) printf(" -> %d", natija);
    printf("\n");

    x = bol(17, 0, &natija);
    printf("17 / 0: %s\n", xato_matni(x));

    x = bol(17, 5, NULL);
    printf("NULL  : %s\n", xato_matni(x));

    return 0;
}