Importing from C (DFDL): restrictions

Problems or restrictions when you import a C header file to create a message model.

  • The C construct typedef is not fully supported; you cannot create messages based on a typedef of an anonymous structure.
  • If an empty struct or union is used as the basis for creating a message, two messages with the same name are created.
  • The C importer does not handle the #if, #ifdef , #else, #elif macros properly. Before importing a C structure, remove these macros from the source file.
  • Hexadecimal constants such as int a[0x80] can cause an exception to be thrown during the import operation. Replace them in the header file before importing.
  • Trigraphs are not supported. Replace trigraphs with the equivalent single character before importing the header file.
  • The C importer requires all programs to be syntactically correct on the target platform. Results are unpredictable if this is not the case. In some circumstances the IBM® Integration Toolkit might crash.
  • When C type int is imported with the option Address size=64bit, elements of schema type xsd:int are created. These have an implicit range of a 32-bit integer. Change the schema type of the element to xsd:long to use values with 64-bit range.
  • Importing C source where an anonymous structure contains an embedded structure might result in an exception. Before you import the header file, ensure that all structures have tags, for example: 
    
		 struct mymessage_tag {
		    int a;
		    struct {                     // anonymous structure...
		       int b1;
		       struct myembstruct_tag {  // ...containing a structure
		          int c1;
		       } c;
		    } b;
		 };
  • An exception might be thrown when an enum with a negative value is imported. Remove the negative value before importing the header file.
  • Structure and element names entirely in uppercase or starting with an underscore might be altered on import.
  • Importing char arrays with 3 or more dimensions, when using the option to import strings as null terminated, can result in an incorrect maxLength facet.
  • Importing char arrays with 3 or more dimensions can cause a Java™ exception to be thrown. Ensure the definitions created are correct.
  • The use of C or C++ reserved keywords causes the import to fail, but nothing in the report specifically indicates this. If your import fails without an obvious reason, examine the C header file carefully and ensure that it compiles correctly. Even if it does compile correctly, it might still contain C++ keywords such as compl, which cause the importer to fail.
  • Bit fields within a C structure are imported. The type is created as xs:hexBinary. Change the type in the DFDL editor to match the C type. Review the values of the DFDL Length, Length Units, Leading Skip, Trailing Skip, Alignment and Alignment Units properties, which might not be set properly.
  • Octal constants such as int a[080] are incorrectly interpreted as decimal constants and must be corrected using the DFDL editor.