elf_flag(3E)

NAME
     elf_flagdata, elf_flagehdr, elf_flagelf, elf_flagphdr, elf_flagscn,
     elf_flagshdr - manipulate flags

SYNOPSIS
     cc [flag ...] file ...  -lelf [library ...]

     #include <libelf.h>
     unsigned elf_flagdata(Elf_Data *data, Elf_Cmd cmd, unsigned flags);
     unsigned elf_flagehdr(Elf *elf, Elf_Cmd cmd, unsigned flags);
     unsigned elf_flagelf(Elf *elf, Elf_Cmd cmd, unsigned flags);
     unsigned elf_flagphdr(Elf *elf, Elf_Cmd cmd, unsigned flags);
     unsigned elf_flagscn(Elf_Scn *scn, Elf_Cmd cmd, unsigned flags);
     unsigned elf_flagshdr(Elf_Scn *scn, Elf_Cmd cmd, unsigned flags);

DESCRIPTION
     These functions manipulate the flags associated with various structures
     of an ELF file.  Given an ELF descriptor (elf), a data descriptor (data),
     or a section descriptor (scn), the functions may set or clear the
     associated status bits, returning the updated bits.  A null descriptor is
     allowed, to simplify error handling; all functions return zero for this
     degenerate case.

     cmd may have the following values.

     ELF_C_CLR         The functions clear the bits that are asserted in
                       flags.  Only the non-zero bits in flags are cleared;
                       zero bits do not change the status of the descriptor.

     ELF_C_SET         The functions set the bits that are asserted in flags.
                       Only the non-zero bits in flags are set; zero bits do
                       not change the status of the descriptor.

     Descriptions of the defined flags bits appear below.

     ELF_F_DIRTY       When the program intends to write an ELF file, this
                       flag asserts the associated information needs to be
                       written to the file.  Thus, for example, a program that
                       wished to update the ELF header of an existing file
                       would call elf_flagehdr with this bit set in flags and
                       cmd equal to ELF_C_SET.  A later call to elf_update
                       would write the marked header to the file.

     ELF_F_LAYOUT      Normally, the library decides how to arrange an output
                       file.  That is, it automatically decides where to place
                       sections, how to align them in the file, etc.  If this
                       bit is set for an ELF descriptor, the program assumes
                       responsibility for determining all file positions.
                       This bit is meaningful only for elf_flagelf and applies
                       to the entire file associated with the descriptor.

     When a flag bit is set for an item, it affects all the subitems as well.
     Thus, for example, if the program sets the ELF_F_DIRTY bit with
     elf_flagelf, the entire logical file is ``dirty.''

EXAMPLE
     The following fragment shows how one might mark the ELF header to be
     written to the output file.

          ehdr = elf32_getehdr(elf);
          /* dirty ehdr ... */
          elf_flagehdr(elf, ELF_C_SET, ELF_F_DIRTY);

SEE ALSO
     elf(3E), elf_end(3E), elf_getdata(3E), elf_getehdr(3E), elf_update(3E).