Get Example source ABAP code based on a different SAP table
ARTICLE
Compatibility in Structure Typing Overview 1 Problems with final alignment gaps 2 Possible solutions when passing structures 3 Possible solutions when passing internal tables
1 Problems with final alignment gaps Final alignment gaps can cause problems when passing structures to formal parameters of subroutines and function modules, if these formal parameters were typed using STRUCTURE. The same problems arise when assigning to field symbols that were typed using STRUCTURE. Final alignment gaps are discussed in more detail under Data Layout of Structures. In non-Unicode systems, the system only checks whether or not the actual parameters are longer than the formal parameters. In Unicode systems, the system also checks whether or not the formal parameter, including final alignment gaps, is a real initial part of the actual parameter. This check uncovers inconsistencies, as the following examples show: Example 1:
Formalparameter Aktualparameter BEGIN OF struc1, BEGIN OF struc2, a TYPE c, a TYPE c, b TYPE p LENGTH 5, b TYPE p LENGTH 5, END OF struc1. c TYPE p LENGTH 3, END OF struc2.
DATA s2 TYPE struc2. PERFORM exp CHANGING s2.
FORM exp CHANGING s1 TYPE struc1. CLEAR s1. ENDFORM. By using the CLEAR s1 statement on the formal parameter s1, the component c of the actual parameter s2 is overwritten with invalid values of the alignment gap. Example 2:
Formalparameter Aktualparameter BEGIN OF struc1, BEGIN OF struc2, a TYPE i, d TYPE i, b TYPE c, e TYPE c, c TYPE c LENGTH 2, f TYPE p LENGTH 15, END OF struc1. END OF struc2.
DATA s2 TYPE struc2. PERFORM exp CHANGING s2.
FORM exp CHANGING s1 TYPE struc1. CLEAR s1. ENDFORM. During passing, the component f of the structure s2 is overwritten with the non-type-specific values of c and the final alignment gap of the structure s1.
2 Possible solutions when passing structures The best solution is to use identical types for the actual and formal parameters. If possible, you should also use TYPES rather than STRUCTURE to assign types, since typing using STRUCTURE is not allowed in classes. In the second example, it is absolutely necessary that you choose one of the types. Mixing the types would have the consequence that read and write accesses result in the processing of non-type-specific contents. This in turn leads to undefined program behavior, which is difficult to analyze. A second possibility is to adapt the actual paramter type so that the type of the formal parameter becomes a real initial part of the actual parameter. You can do this by incorporating an ABAP Code Snippet this: Formalparameter Aktualparameter BEGIN OF struc1, BEGIN OF struc2. ABAP Code Snippet b TYPE p LENGTH 5, TYPES: c TYPE p LENGTH 3, END OF struc1. END OF struc2. This ensures that the alignment gaps of the formal parameter have the same coverage as the alignment gaps of the actual parameter and, therefore, the actual values cannot be overwritten.
3 Possible solutions when passing internal tables Problems can also arise when using TABLES parameters with STRUCTURE typing. If you pass an internal table with a header line to a TABLES parameter, both the header and the table body are passed, so therefore the same inconsistencies occur for the header as with the transfer of non-type-specific structures. In cases, where the header is not used as a return parameter, the problem can be avoided by passing only the table body. This is done by using square brackets after the table name, as shown in the following example: DATA itab TYPE TABLE OF struc2 WITH HEADER LINE.
