code snippets need markdown for pretty printing.

```c
#include <stdio.h>
#include <string.h>

final code version to try for repro:

int main(int argc, char ** argv)
{
char buf[32];
memset(buf, 0xFF, 32);
snprintf(buf, 16, "%s", "1234567890ABCDEFabcdef");

if (buf[15] == 'F')
{
printf("DANGER!!!\n");
}
else
{
printf("FAILED\n");
}

printf(buf);
}
```

seems okay to me, if snprintf's second argument is 1-indexed and buf elements are 0-indexed.
I can't explain the presence of last character in buf. see output of line 19(the character is invisible in preview )->
```c
1234567890ABCDEF                  
```

or why both #include lines are optional for successful compilation using tcc.

used Windows 10 1909 with tcc-0.9.27