There are many dangerous in Zabbix any versions.

For example, in include/db.h
#define TRIGGER_EXPRESSION_LEN_MAX TRIGGER_EXPRESSION_LEN+1

It should be with bracket () like following
#define TRIGGER_EXPRESSION_LEN_MAX (TRIGGER_EXPRESSION_LEN+1)

The reason is following
int a = TRIGGER_EXPRESSION_LEN_MAX * 4;

The programer think a is TRIGGER_EXPRESSION_LEN * 4 + 4. But a is TRIGGER_EXPRESSION_LEN + 4.
It is just amateurs' miss!