#includeint main(void) { int a = 10, b = 20, c = 30; printf("\n %d..%d..%d \n", a+b+c, (b = b*2), (c = c*2)); return 0; }
110..40..60
#includeint* inc(int val) { int a = val; a++; return &a; } int main(void) { int a = 10; int *val = inc(a); printf("\n Incremented value is equal to [%d] \n", *val); return 0; }
#includeint main(int argc, char *argv[]) { int i = 0; char buff[100]; memset(buff,0,sizeof(buff)); strncpy(buff, argv[0], sizeof(buff)); memset(argv[0],0,strlen(buff)); strncpy(argv[0], "NewName", 7); // Simulate a wait. Check the process // name at this point. for(;i<0xffffffff 0="" i="" pre="" return="">
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#includeint main(void) { char *ptr = "Linux"; *ptr = 'T'; printf("\n [%s] \n", ptr); return 0; }
#includeint main(void) { char *ptr = "Linux"; printf("\n [%c] \n",*ptr++); printf("\n [%c] \n",*ptr); return 0; }
[L] [i]
int func(void *ptr)
#includevoid func(void) { printf("\n Cleanup function called \n"); return; } int main(void) { int i = 0; atexit(func); for(;i<0xffffff _exit="" i="" pre=""> Answer: This behavior is due to the use of function _exit(). This function does not call the clean-up functions like atexit() etc. If atexit() is required to be called then exit() or ‘return’ should be used.
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#includeint main(int argc, char *argv[]) { char *ptr = (char*)malloc(10); if(NULL == ptr) { printf("\n Malloc failed \n"); return -1; } else if(argc == 1) { printf("\n Usage \n"); } else { memset(ptr, 0, 10); strncpy(ptr, argv[1], 9); while(*ptr != 'z') { if(*ptr == '') break; else ptr++; } if(*ptr == 'z') { printf("\n String contains 'z'\n"); // Do some more processing } free(ptr); } return 0; }
#includevoid main(void) { char *ptr = (char*)malloc(10); if(NULL == ptr) { printf("\n Malloc failed \n"); return; } else { // Do some processing } return; }
#includevoid main(void) { char *ptr = (char*)malloc(10); if(NULL == ptr) { printf("\n Malloc failed \n"); return; } else { // Do some processing free(ptr); } return; }
#includeint main(int argc, char *argv[]) { int flag = 0; char passwd[10]; memset(passwd,0,sizeof(passwd)); strcpy(passwd, argv[1]); if(0 == strcmp("LinuxGeek", passwd)) { flag = 1; } if(flag) { printf("\n Password cracked \n"); } else { printf("\n Incorrect passwd \n"); } return 0; }
$ ./psswd aaaaaaaaaaaaa Password cracked
Note from author : These days the compilers internally detect the possibility of stack smashing and so they store variables on stack in such a way that stack smashing becomes very difficult. In my case also, the gcc does this by default so I had to use the the compile option ‘-fno-stack-protector’ to reproduce the above scenario.
#includeAnswer: The hidden problem with the code above is the use of the function gets(). This function accepts a string from stdin without checking the capacity of buffer in which it copies the value. This may well result in buffer overflow. The standard function fgets() is advisable to use in these cases.int main(void) { char buff[10]; memset(buff,0,sizeof(buff)); gets(buff); printf("\n The buffer entered is [%s]\n",buff); return 0; }
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#include <stdio.h>
#include <stdlib.h>
int main()
{
int m = abs(200); // m is assigned to 200
int n = abs(-400); // n is assigned to -400
printf("Absolute value of m = %d\n", m);
printf("Absolute value of n = %d \n",n);
return 0;
}
|
| Absolute value of m = 200 Absolute value of n = 400 |
| S.no |
Function
|
Description
|
| 1 | abs ( ) | This function returns the absolute value of an integer. The absolute value of a number is always positive. Only integer values are supported in C. |
| 2 | floor ( ) | This function returns the nearest integer which is less than or equal to the argument passed to this function. |
| 3 | round ( ) | This function returns the nearest integer value of the float/double/long double argument passed to this function. If decimal value is from ”.1 to .5″, it returns integer value less than the argument. If decimal value is from “.6 to .9″, it returns the integer value greater than the argument. |
| 4 | ceil ( ) | This function returns nearest integer value which is greater than or equal to the argument passed to this function. |
| 5 | sin ( ) | This function is used to calculate sine value. |
| 6 | cos ( ) | This function is used to calculate cosine. |
| 7 | cosh ( ) | This function is used to calculate hyperbolic cosine. |
| 8 | exp ( ) | This function is used to calculate the exponential “e” to the xth power. |
| 9 | tan ( ) | This function is used to calculate tangent. |
| 10 | tanh ( ) | This function is used to calculate hyperbolic tangent. |
| 11 | sinh ( ) | This function is used to calculate hyperbolic sine. |
| 12 | log ( ) | This function is used to calculates natural logarithm. |
| 13 | log10 ( ) | This function is used to calculates base 10 logarithm. |
| 14 | sqrt ( ) | This function is used to find square root of the argument passed to this function. |
| 15 | pow ( ) | This is used to find the power of the given number. |
| 16 | trunc.(.) | This function truncates the decimal value from floating point value and returns integer value. |
