Verify if the file attached to the BFD abfd is compatible with the format format (i.e., one of bfd_object, bfd_archive or bfd_core).

If the BFD has been set to a specific target before the call, only the named target and format combination is checked. If the target has not been set, or has been set to default, then all the known target backends is interrogated to determine a match. If the default target matches, it is used. If not, exactly one target must recognize the file, or an error results.

The function returns TRUE on success, otherwise FALSE with one of the following error codes:

• bfd_error_invalid_operation - if format is not one of bfd_object, bfd_archive or bfd_core.
• bfd_error_system_call - if an error occured during a read - even some file mismatches can cause bfd_error_system_calls.
• file_not_recognised - none of the backends recognised the file format.
• bfd_error_file_ambiguously_recognized - more than one backend recognised the file format.

When calling bfd_check_format (or bfd_check_format_matches), any underlying file descriptor will be kept open for the duration of the call. This is done to avoid races when another thread calls bfd_cache_close_all. In this scenario, the thread calling bfd_check_format must call bfd_cache_close itself.

Like bfd_check_format, except when it returns FALSE with bfd_errno set to bfd_error_file_ambiguously_recognized. In that case, if matching is not NULL, it will be filled in with a NULL-terminated list of the names of the formats that matched, allocated with malloc. Then the user may choose a format and try again.

When done with the list that matching points to, the caller should free it.

This function sets the file format of the BFD abfd to the format format. If the target set in the BFD does not support the format requested, the format is invalid, or the BFD is not open for writing, then an error occurs.

Return a pointer to a const string invalid, object, archive, core, or unknown, depending upon the value of format.