I'm a new coder and I'm learning C, after studying some of the basics I tried doing some LeetCode exercises, and one of them is a Roman to Integer converter, after some trying I moved from the LeetCode site to Visual Studio to try and do a functioning code since for me at least the assisting tools of the VStudio are very helpful, in there I did a code that worked, I think, smoothly, but when I copied it into LeetCode and did some tweaks it returned me an Run Time Error, can anyone help me discovering what is causing the problem?
Sorry for any mistakes, English is not my first Language and it's the first time I'm posting on StackOverflow.
The code that I'm using on Visual Studio with the testcase "MCMXCIV":
#include <stdio.h>
char s[] = {'M','C','M','X','C','I','V'};
int vals[sizeof(s)];
int sum = 0;
int main(void) {
//Getting the info about how many characters there are in the Roman Numeral
int nchar = sizeof(s);
//For loop that assigns each Roman Numeral its correspondant in the Arabic Numbers
for (int i = 0; i < nchar; i ) {
if (s[i] == 'I') {
vals[i] = 1;
}
else if (s[i] == 'V') {
vals[i] = 5;
}
else if (s[i] == 'X') {
vals[i] = 10;
}
else if (s[i] == 'L') {
vals[i] = 50;
}
else if (s[i] == 'C') {
vals[i] = 100;
}
else if (s[i] == 'D') {
vals[i] = 500;
}
else {
vals[i] = 1000;
}
}
//For loop that get the sum in Arabics
for (int i = 0; i < nchar; i ) {
if (i != nchar - 1 && vals[i] < vals[i 1]) {
sum = sum vals[i 1] - vals[i];
i ;
}
else {
sum = sum vals[i];
}
}
printf("Your Roman Numer is %i in Arabic Numbers!", sum);
return 0;
}
The slightly tweaked code that I'm using on LeetCode(with the same testcase):
int romanToInt(char * s){
//variables used int the loops
int nchar = sizeof(s);
int vals[sizeof(s)];
int sum = 0;
//for loop that assigns each Roman Number to its Arabic correspondant
for (int i = 0; i < nchar; i ) {
if (s[i] == 'I') {
vals[i] = 1;
}
else if (s[i] == 'V') {
vals[i] = 5;
}
else if (s[i] == 'X') {
vals[i] = 10;
}
else if (s[i] == 'L') {
vals[i] = 50;
}
else if (s[i] == 'C') {
vals[i] = 100;
}
else if (s[i] == 'D') {
vals[i] = 500;
}
else {
vals[i] = 1000;
}
}
//sum algorithm
for (int i = 0; i < nchar; i ) {
if (i != nchar - 1 && vals[i] < vals[i 1]) {
sum = sum vals[i 1] - vals[i];
i ;
}
else {
sum = sum vals[i];
}
}
return sum;
}
The Error I'm getting on LeetCode:
=================================================================
==34==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000014 at pc 0x563ee0bf8176 bp 0x7ffd0819f880 sp 0x7ffd0819f870
READ of size 1 at 0x602000000014 thread T0
#2 0x7f786db5b0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6 0x270b2)
0x602000000014 is located 0 bytes to the right of 4-byte region [0x602000000010,0x602000000014)
allocated by thread T0 here:
#0 0x7f786e7a0bc8 in malloc (/lib/x86_64-linux-gnu/libasan.so.5 0x10dbc8)
#3 0x7f786db5b0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6 0x270b2)
Shadow bytes around the buggy address:
0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa[04]fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==34==ABORTING
Sorry for any mistakes, English is not my first Language and it's the first time I'm posting on StackOverflow.
CodePudding user response：
The sizeof operator evaluates to the size of its operand's object representation in bytes.
With
char s[] = {'M','C','M','X','C','I','V'};
s has the type char [7], and sizeof s is 7 bytes.
With
int romanToInt(char *s)
s has the type char *, and sizeof s is platform dependent. Common sizes for a pointer are 8 bytes (64-bit) and 4 bytes (32-bit).
In the LeetCode environment, the argument to the function is a properly null-terminated string, and the problem description states
It is guaranteed that
sis a valid roman numeral in the range[1, 3999].
Which means the input can be of length [1, 15].
Your loop always iterates sizeof (char *) times, and will surely read past the end of shorter strings, accessing memory it should not. This is Undefined Behaviour, but is caught by ASan.
Use strlen to find the length of the input, or loop until you reach the null-terminating byte ('\0').
for (size_t i = 0; s[i] != '\0'; i ) {
/* ... */
}
Note that this will not work with your local version, as
char s[] = {'M','C','M','X','C','I','V'};
lacks the null-terminating byte. Initialize your array with a string literal
char s[] = "MCMXCIV";
to include one.