I received a new version of the OSS ASN.1 tools. When the same ASN.1 input file that I used with the older compiler is passed to the new compiler the generated header file is different. How do I instruct the compiler to generate the same header file as it previously generated?

All upgraded versions of the ASN.1 compiler can produce header files that are fully backward compatible. To instruct the ASN.1 compiler to generate header files compatible with a previous version, simply use the -compat option with the corresponding version number as an argument. For example, the command-line option:

-compat v4.2.6

instructs the ASN.1 compiler to generate header files compatible with version 4.2.6. Similarly, the command-line option:

-compat v3.0

instructs the ASN.1 compiler to generate header files compatible with version 3.0.

Another yet better approach is to use the -gen and -keep ASN.1 compiler command line options:

-gen myfile.gen -keep

The above options will result in generation of the myfile.gen file with all the directives captured for a given ASN.1 compiler release. Then you can use myfile.gen with later releases of the ASN.1 compiler to force it to generate the same names in the output header files.

For more information on backward compatibility, refer to the Backward Compatibility section.

---

The samples included with some of the Knowledge Center answers are meant for your general understanding of the OSS products. Different versions of the products might produce slightly different outputs. Consult the products documentation and samples for the most up-to-date products information and code examples.