According to the ANSI C standard "7.5 Errors <errno.h>" section 3[1], 
"The value of errno is zero at program startup,
but is never set to zero by any library function."

The "program startup" is also defined in ANSI C standard 
"5.1.2.2.1 Program startup" section 1[2],
"The function called at program startup is named main."

Therefore, it should be reasonable to expect 
errno be zero when main is executed.

However, we found that 
the following program would get non-zero errno under some circumstances.

```
/* errno.c */
#include <errno.h>
#include <stdio.h>

int main()
{
	printf("errno: %d\n", errno);
	return 0;
}


$ riscv64-linux-gcc -O0 -g -static -o errno_st errno.c

[   51.968765] random: fast init done
/mnt # ./errno
errno: 11

[   51.968765] random: fast init done
[  262.517056] crng init done
/mnt # ./errno
errno: 0
```

If the above program is statically-linked, 
and if the program is executed before "crng init done",
the errno will not be zero when entering main.

There seems to be syscall (__getrandom) before main is entered,
and if the crng is not initialized, 
the syscall will fail causing the errno to be set.
(_dl_get_origin -> __libc_malloc -> ptmalloc_init -> tcache_key_initialize -> __getrandom)

Thanks to Florian's suggestion:
"Hiding the getrandom failure is probably sufficient.  All other
failures in malloc will lead to the process failing to start, so those
errors don't need to be masked."

We should clear the errno for the getrandom failure

Related discussion:
https://sourceware.org/pipermail/libc-help/2022-September/006301.html