c - finding memory access violation for a code -
i noob on valgrind. gcc compiler compiler gave me go flag online compiler gave me hard time need submit code. please me finding memory access violation below code
#include<stdio.h> #include<string.h> #include<stdlib.h> #include<string.h> #include<ctype.h> #include"railfence.h" #define rail 2 char* getcipher(char plaintext[]) { int strln; int i; int j; int k = 0; char *result; char **arr; strln = strlen(plaintext); if (strln == 0 || strln > 20) return "-1"; ( i=0 ; < strln ; i++) if (!isupper(plaintext[i])) return "-1"; arr = (char **) malloc ( rail*sizeof(char) ); ( i=0 ; < rail ; i++) arr[i] = (char *) malloc ( strln*sizeof(char) ); k = 0; ( = 0 ; < strln ; i++ ) ( j = 0 ; j < 2 ; j++ ) { if ( (i+j)&1 ) arr[j][i] = '.'; else arr[j][i] = plaintext[k++]; } result = (char *) malloc (sizeof(char) * strln); k=0; strln = strlen(*arr); ( = 0 ; < rail ; i++ ) { ( j = 0 ; j < strln ; j++ ) if ( arr[i][j] != '.' ) result[k++] = arr[i][j]; free(arr[i]); } free(arr); return result; } main.c
#include <stdio.h> #include"railfence.h" int main() { //testcase 1 { printf("\ntestcase 1\n"); char plaintext[]="abcdefgh"; char * ciphertext= getcipher(plaintext); if(ciphertext!=null) printf("%s\n",ciphertext); } } valgrind log :
==31753== memcheck, memory error detector ==31753== copyright (c) 2002-2013, , gnu gpl'd, julian seward et al. ==31753== using valgrind-3.10.0.svn , libvex; rerun -h copyright info ==31753== command: ./main ==31753== testcase 1 ==31753== invalid write of size 8 ==31753== @ 0x40079f: getcipher (railfence.c:30) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd040 0 bytes inside block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 8 ==31753== @ 0x40080f: getcipher (railfence.c:38) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd040 0 bytes inside block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 8 ==31753== @ 0x4007eb: getcipher (railfence.c:36) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd048 6 bytes after block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 8 ==31753== @ 0x400869: getcipher (railfence.c:43) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd040 0 bytes inside block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 1 ==31753== @ 0x4c2e0f4: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x400873: getcipher (railfence.c:43) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd098 0 bytes after block of size 8 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40079e: getcipher (railfence.c:30) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 8 ==31753== @ 0x4008a0: getcipher (railfence.c:46) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd040 0 bytes inside block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 8 ==31753== @ 0x4008d9: getcipher (railfence.c:47) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd040 0 bytes inside block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 8 ==31753== @ 0x400909: getcipher (railfence.c:49) ==31753== 0x400977: main (main.c:14) ==31753== address 0x51fd040 0 bytes inside block of size 2 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x40076f: getcipher (railfence.c:26) ==31753== 0x400977: main (main.c:14) ==31753== ==31753== invalid read of size 1 ==31753== @ 0x4c2e0f4: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x4ea7c7b: puts (ioputs.c:36) ==31753== 0x40098e: main (main.c:16) ==31753== address 0x51fd138 0 bytes after block of size 8 alloc'd ==31753== @ 0x4c2ab80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==31753== 0x400859: getcipher (railfence.c:41) ==31753== 0x400977: main (main.c:14) ==31753== acegbdfh ==31753== ==31753== heap summary: ==31753== in use @ exit: 8 bytes in 1 blocks ==31753== total heap usage: 4 allocs, 3 frees, 26 bytes allocated ==31753== ==31753== leak summary: ==31753== lost: 8 bytes in 1 blocks ==31753== indirectly lost: 0 bytes in 0 blocks ==31753== possibly lost: 0 bytes in 0 blocks ==31753== still reachable: 0 bytes in 0 blocks ==31753== suppressed: 0 bytes in 0 blocks ==31753== rerun --leak-check=full see details of leaked memory ==31753== ==31753== counts of detected , suppressed errors, rerun with: -v ==31753== error summary: 47 errors 9 contexts (suppressed: 0 0)
try change line of code
arr = (char **) malloc ( rail*sizeof(char) ); with this
arr = (char **) malloc ( rail*sizeof(char*) );
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