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Add &default_insert attribute for tables

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This is based on the discussion in zeek/zeek#2668. Using &default with tables
can be confusing as the default value is not inserted. The following example
prints an empty table at the end even new Service records was instantiated.

    type Service: record {
        occurrences: count &default=0;
        last_seen: time &default=network_time();
    };

    global services: table[string] of Service &default=Service();

    event zeek_init()
        {
        services["http"]$occurrences += 1;
        services["http"]$last_seen = network_time();

        print services;
        }

Changing above &default to &default_insert will insert the newly created
default value upon a missed lookup and act less surprising.

Other examples that caused confusion previously revolved around table of sets
 or table of vectors and `add` or `+=` not working as expected.

    tbl_of_vector["http"] += 1
    add tbl_of_set["http"][1];
This commit is contained in:
Arne Welzel 2023-07-07 17:05:00 +02:00
parent 81ce83590d
commit 431767d04b
22 changed files with 230 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

41
src/Attr.cc
View file

@ -16,9 +16,12 @@ namespace zeek::detail
const char* attr_name(AttrTag t)
{
// Do not collapse the list.
// clang-format off
static const char* attr_names[int(NUM_ATTRS)] = {
"&optional",
"&default",
"&default_insert",
"&redef",
"&add_func",
"&delete_func",
@ -42,6 +45,7 @@ const char* attr_name(AttrTag t)
"&is_used",
"&ordered",
};
// clang-format on
return attr_names[int(t)];
}
@ -359,8 +363,35 @@ void Attributes::CheckAttr(Attr* a)
}
break;
case ATTR_DEFAULT_INSERT:
{
if ( ! type->IsTable() )
{
Error("&default_insert only applicable to tables");
break;
}
if ( Find(ATTR_DEFAULT) )
{
Error("&default and &default_insert cannot be used together");
break;
}
std::string err_msg;
if ( ! check_default_attr(a, type, global_var, in_record, err_msg) &&
! err_msg.empty() )
Error(err_msg.c_str());
break;
}
case ATTR_DEFAULT:
{
if ( Find(ATTR_DEFAULT_INSERT) )
{
Error("&default and &default_insert cannot be used together");
break;
}
std::string err_msg;
if ( ! check_default_attr(a, type, global_var, in_record, err_msg) &&
! err_msg.empty() )
@ -672,11 +703,13 @@ bool Attributes::operator==(const Attributes& other) const
bool check_default_attr(Attr* a, const TypePtr& type, bool global_var, bool in_record,
std::string& err_msg)
{
ASSERT(a->Tag() == ATTR_DEFAULT || a->Tag() == ATTR_DEFAULT_INSERT);
std::string aname = attr_name(a->Tag());
// &default is allowed for global tables, since it's used in
// initialization of table fields. It's not allowed otherwise.
if ( global_var && ! type->IsTable() )
{
err_msg = "&default is not valid for global variables except for tables";
err_msg = aname + " is not valid for global variables except for tables";
return false;
}
@ -707,7 +740,7 @@ bool check_default_attr(Attr* a, const TypePtr& type, bool global_var, bool in_r
return true;
}
a->GetExpr()->Error("&default value has inconsistent type", type.get());
a->GetExpr()->Error(util::fmt("%s value has inconsistent type", aname.c_str()), type.get());
return false;
}
@ -725,7 +758,7 @@ bool check_default_attr(Attr* a, const TypePtr& type, bool global_var, bool in_r
FuncType* f = atype->AsFuncType();
if ( ! f->CheckArgs(tt->GetIndexTypes()) || ! same_type(f->Yield(), ytype) )
{
err_msg = "&default function type clash";
err_msg = aname + " function type clash";
return false;
}
@ -748,7 +781,7 @@ bool check_default_attr(Attr* a, const TypePtr& type, bool global_var, bool in_r
return true;
}
err_msg = "&default value has inconsistent type";
err_msg = aname + " value has inconsistent type";
return false;
}