# LoadHeaderFile

## Description

This command allows you to apply type declarations from a C header file to the program. IDA reads and parses the specified header file as a C compiler does. In other words, it mimics the front-end of a C compiler with some restrictions:

* Only type declarations are allowed. The function definitions in the input file are skipped.
* Not all C++ header files are not supported, only simple classes can be parsed.
* The compiler specific predefined macros are not defined, you have to define them manually in the header file.

Don't forget to specify the compiler and memory model in the compiler setup dialog box (Options → Compiler...) before loading a header file. All type declarations found in the input file are stored in the current database in the form of a type library. These type declarations can be used to define new structure and enumeration definitions.

In the case of an error in the input file, the error messages appear in the message window. In any case, the function declarations that are already parsed are not deleted from the database. IDA stops parsing the input file when 20 errors occur. IDA 7.7 introduced an alternative header file parser based on libclang.


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