[Valgrind-users] Valgrind not finding issue with writing/reading past array?

[Grant S. <mat...@gm...>]

So I noticed something in my code that looked wrong to me, but valgrind
didn't report anything. I made a small example of it, and still no
findings. I'm sure this code is reading/writing past its array. But valgind
doesn't say anything.

I'm I not understanding something or is this a bug.

Using:
valgrind-3.19.0, gcc 4.8.5, CentOS 7

I also tried
valgrind-3.19.0, gcc 7.3.1, Amazon Linux 2

Here is the code.
------
#include <string.h>
#include <stdio.h>

int main()
{
   char retStr[32];

   // this is bad right? 40 bytes when above was 32?
   memset(retStr, 'F', 40);

   // These are "writing"  past the allocated memory?
   retStr[32] = 'A';
   retStr[33] = 'B';

   // These should be fine
   printf("***********  retStr is %c\n", retStr[30]);
   printf("***********  retStr is %c\n", retStr[31]);

   // These are reading past allocated memory?
   printf("***********  retStr is %c\n", retStr[32]);
   printf("***********  retStr is %c\n", retStr[33]);

   return 0;
}
---


Compiled:
"gcc filename.cxx"

Ran via this command
"valgrind ./a.out"