Linux Startup and Shutdown Question:
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What is the output of this program?

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

int main()
{
int ret;
int ptr;
ptr = (int )malloc(sizeof(int)*10);
free(ptr);
free(ptr);
return 0;
}
a) it will print nothing
b) it will give segmentaion fault
c) undefined behaviour
d) none of the mentioned

Answer:

c) undefined behaviour
Explanation:
If the free() has already called before, undefined behaviour occurs.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
*** glibc detected *** ./san: double free or corruption (fasttop): 0x08f1b008 ***
======= Backtrace: =========
/lib/libc.so.6[0x4a6489f2]
./san[0x8048425]
/lib/libc.so.6(__libc_start_main+0xf3)[0x4a5e96b3]
./san[0x8048361]
======= Memory map: ========
08048000-08049000 r-xp 00000000 fd:01 394194 /home/google/san
08049000-0804a000 rw-p 00000000 fd:01 394194 /home/google/san
08f1b000-08f3c000 rw-p 00000000 00:00 0 [heap]
4a5ab000-4a5cc000 r-xp 00000000 fd:01 785334 /lib/ld-2.14.90.so
4a5cc000-4a5cd000 r-p 00020000 fd:01 785334 /lib/ld-2.14.90.so
4a5cd000-4a5ce000 rw-p 00021000 fd:01 785334 /lib/ld-2.14.90.so
4a5d0000-4a77a000 r-xp 00000000 fd:01 789110 /lib/libc-2.14.90.so
4a77a000-4a77b000 -p 001aa000 fd:01 789110 /lib/libc-2.14.90.so
4a77b000-4a77d000 r-p 001aa000 fd:01 789110 /lib/libc-2.14.90.so
4a77d000-4a77e000 rw-p 001ac000 fd:01 789110 /lib/libc-2.14.90.so
4a77e000-4a781000 rw-p 00000000 00:00 0
4a7e0000-4a7fc000 r-xp 00000000 fd:01 789128 /lib/libgcc_s-4.6.2-20111027.so.1
4a7fc000-4a7fd000 rw-p 0001b000 fd:01 789128 /lib/libgcc_s-4.6.2-20111027.so.1
b76f4000-b76f5000 rw-p 00000000 00:00 0
b770d000-b770f000 rw-p 00000000 00:00 0
b770f000-b7710000 r-xp 00000000 00:00 0 [vdso]
bfc0a000-bfc2b000 rw-p 00000000 00:00 0 [stack]
Aborted (core dumped)
[root@localhost google]#

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In which condition this prgram will print the string "google"? #include<stdio.h> #include<stdlib.h> int main() { int ptr; ptr = (int )malloc(sizeof(int)*10); if (ptr == NULL) printf("googlen"); return 0; } a) if the memory could not be allocated to the pointer "ptr" b) if the memory has been allocated to the pointer "ptr" successfully c) it will never print d) none of the mentioned	What is the output of this program? #include<stdio.h> #include<stdlib.h> int main() { int ptr1; while(1){ ptr1 = malloc(10241024); if(ptr1 == 0) break; sleep(1); printf("googlen"); free(ptr1); } return 0; } a) it will print "google" until the process has been stopeed by any signal b) it will print nothing c) segmentation fault d) none of the mentioned

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What is the output of this program? #include<stdio.h> #include<stdlib.h> int main() { int ret; int *ptr; ptr = (int *)malloc(sizeof(int)*10); free(ptr); free(ptr); return 0; } a) it will print nothing b) it will give segmentaion fault c) undefined behaviour d) none of the mentioned

Answer:

Linux Startup and Shutdown Question:
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What is the output of this program?

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

int main()
{
int ret;
int ptr;
ptr = (int )malloc(sizeof(int)*10);
free(ptr);
free(ptr);
return 0;
}
a) it will print nothing
b) it will give segmentaion fault
c) undefined behaviour
d) none of the mentioned