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POWrong values stored and other
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copied!<p>I made this program:<br></p> <p><strong>llist:</strong></p> <pre><code>typedef struct linked_list { int val; int n; struct linked_list *next; }llist; </code></pre> <p><strong>addelem function:</strong></p> <pre><code>void addelem(llist *list,int val) { llist *tmp=(llist *)malloc(sizeof(llist)); //create new element tmp->val=val; //assign value to tmp tmp->next=NULL; //set next to NULL // printf("addelem entered\n"); if(list->next!=NULL) //if this is not the last element { addelem(list->next,val); //recursion } else { tmp->n=list->n + 1; list->next=(llist *)malloc(sizeof(llist)); //allocate memory list->next=tmp; //add to list } // printf("addelem exited\n"); free(tmp); } </code></pre> <p><strong>remelem function:</strong></p> <pre><code>void remelem(llist *list) { int f=0; if(list->n==0 && list->next==NULL) goto dontremove; if(1) { if(list->next!=NULL) { if(list->next->next==NULL) { f=1; } remelem(list->next); } else { free(list); } if(f==1) { list->next=NULL; } } else { dontremove: printf("cant be removed even if the next message is 'Element removed.'\n"); } //end } </code></pre> <p><strong>show function:</strong> </p> <pre><code>void show(llist *list) { printf("Element number: %d\nElement Value: %d\n",list->n,list->val); if(list->next!=NULL) { show(list->next); } else { printf("\nTotal number of elems: %d\n",list->n);; } } </code></pre> <p><strong>main function:</strong></p> <pre><code>int main() { int i,n,ch; llist *list=(llist *)malloc(sizeof(llist)); list->next=NULL; list->n=0; list->val=0; menu: //menu label printf("1.Add element.\n"); printf("2.Remove element.\n3.Show elements\n0.Exit.\n"); scanf("%d",&ch); switch(ch) { case 1: printf("\nEnter value.\n"); scanf("%d",&n); addelem(list,n); printf("Element added\n"); break; case 2: remelem(list); printf("\nElement removed.\n"); break; case 3: show(list); break; case 0: goto end; //end break; } goto menu; //show menu again end: //end label return 0; } </code></pre> <p>Output:</p> <pre><code>1.Add element. 2.Remove element. 3.Show elements 0.Exit. 1 Enter value. 22 Element added 1.Add element. 2.Remove element. 3.Show elements 0.Exit. 1 Enter value. 4 Element added 1.Add element. 2.Remove element. 3.Show elements 0.Exit. 2 Element removed. 1.Add element. 2.Remove element. 3.Show elements 0.Exit. 3 Element number: 0 Element Value: 0 Element number: 1 Element Value: 161701936 Total number of elems: 1 </code></pre> <p>the values are different from the ones I typed,. My first question is that why does this happen?(probably a silly mistake) and how can i fix it to print correct value.</p> <p><br> <br> and here is another output:</p> <pre><code>1.Add element. 2.Remove element. 3.Show elements 0.Exit. 1 Enter value. 22 Element added 1.Add element. 2.Remove element. 3.Show elements 0.Exit. 1 Enter value. 23 Element added 1.Add element. 2.Remove element. 3.Show elements 0.Exit. 2 Element removed. 1.Add element. 2.Remove element. 3.Show elements 0.Exit. 1 Enter value. 22 Segmentation fault (core dumped) </code></pre> <p>In this, first I add an element, then I remove it,but if I add the element again I get segmentation fault, Can anyone explain why does this happen and how to fix it?.</p> <p>And if at first I add an element and I remove it, then this is what I get:</p> <pre><code>*** glibc detected *** ./llist: double free or corruption (fasttop): 0x0855b018 *** ======= Backtrace: ========= certain memory addresses ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:01 1969473 /path/to/this/prog 08049000-0804a000 r--p 00000000 08:01 1969473 /path/to/this/prog 0804a000-0804b000 rw-p 00001000 08:01 1969473 /path/to/this/prog 0855b000-0857c000 rw-p 00000000 00:00 0 [heap] b758e000-b75aa000 r-xp 00000000 08:01 3802036 /lib/i386-linux-gnu/libgcc_s.so.1 b75aa000-b75ab000 r--p 0001b000 08:01 3802036 /lib/i386-linux-gnu/libgcc_s.so.1 b75ab000-b75ac000 rw-p 0001c000 08:01 3802036 /lib/i386-linux-gnu/libgcc_s.so.1 b75c3000-b75c4000 rw-p 00000000 00:00 0 b75c4000-b7767000 r-xp 00000000 08:01 3805265 /lib/i386-linux-gnu/libc-2.15.so b7767000-b7768000 ---p 001a3000 08:01 3805265 /lib/i386-linux-gnu/libc-2.15.so b7768000-b776a000 r--p 001a3000 08:01 3805265 /lib/i386-linux-gnu/libc-2.15.so b776a000-b776b000 rw-p 001a5000 08:01 3805265 /lib/i386-linux-gnu/libc-2.15.so b776b000-b776e000 rw-p 00000000 00:00 0 b7782000-b7787000 rw-p 00000000 00:00 0 b7787000-b7788000 r-xp 00000000 00:00 0 [vdso] b7788000-b77a8000 r-xp 00000000 08:01 3805277 /lib/i386-linux-gnu/ld-2.15.so b77a8000-b77a9000 r--p 0001f000 08:01 3805277 /lib/i386-linux-gnu/ld-2.15.so b77a9000-b77aa000 rw-p 00020000 08:01 3805277 /lib/i386-linux-gnu/ld-2.15.so bf969000-bf98a000 rw-p 00000000 00:00 0 [stack] Aborted (core dumped) </code></pre> <p>can anyone please tell why these errors have occured?</p> <p>I use Ubuntu 12.04</p> <p>Thank You</p>

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