Attribute: pack

The pragma defines how a data structure is packed during the allocation. The attribute has to be inserted above the data structure and affects the packing of the entire structure.

Syntax:

‎{attribute 'pack_mode' := ' <pack mode value> '}‎

Insert location: Above the declaration of the data structure

Table 548: Possible values for `‎<pack mode value>‎`
`‎<pack mode value>‎`	Associated packing method	Description
0	Aligned	All variables are allocated to byte addresses. There are no memory gaps.
1	1-byte-aligned
2	2-byte-aligned	There are 1-byte variables at byte addresses 2-byte variables at addresses divisible by 2. A maximum gap of 1 byte results. 4-byte variables at addresses divisible by 2. A maximum gap of 1 byte results. 8-byte variables at addresses divisible by 2. A maximum gap of 1 byte results. Strings always at byte addresses. No gaps result.
4	4-byte-aligned	There are 1-byte variables at byte addresses 2-byte variables at addresses divisible by 2. A maximum gap of 1 byte results. 4 byte variables at addresses divisible by 4. A maximum gap of 3 byte results. 8-byte variables at addresses divisible by 4. A maximum gap of 3 byte results. Strings always at byte addresses. No gaps result.
8	8-byte-aligned	There are 1-byte variables at byte addresses 2-byte variables at addresses divisible by 2. A maximum gap of 1 byte results. 4 byte variables at addresses divisible by 4. A maximum gap of 3 byte results. 8 byte variables at addresses divisible by 8. A maximum gap of 7 byte results. Strings always at byte addresses. No gaps result.

Depending on the structure, there may be no difference in the memory mapping of the individual modes. For example, the memory distribution of a structure with the ‎{attribute 'pack mode' := '4'}‎ pragma can correspond to that of ‎{attribute 'pack mode' := '8'}‎.

Arrays of structures

If the structures are combined in arrays, then bytes are added at the end of the structure so that the next structure is aligned.

NOTICE

If the “Compatibility layout” option is selected in the symbol configuration and at the same time the attribute ‎'pack_mode'‎ is used in the code, then problems can occur due to unintentional memory misalignment.

Example 1
Example 2
Example 3
Behavior without ‎'pack-mode'‎
Negative effects when using ‎'pack-mode'‎