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.\" $Id: gelf_getrel.3,v 1.2 2020/05/18 06:46:23 jsg Exp $
.\"
.Dd April 22, 2019
.Dt GELF_GETREL 3
.Os
.Sh NAME
.Nm gelf_getrel ,
.Nm gelf_update_rel
.Nd read and update ELF relocation entries
.Sh LIBRARY
.Lb libelf
.Sh SYNOPSIS
.In gelf.h
.Ft "GElf_Rel *"
.Fn gelf_getrel "Elf_Data *data" "int ndx" "GElf_Rel *rel"
.Ft int
.Fn gelf_update_rel "Elf_Data *data" "int ndx" "GElf_Rel *rel"
.Sh DESCRIPTION
These convenience functions are used to retrieve and update class-dependent
.Vt Elf32_Rel
or
.Vt Elf64_Rel
structures in an ELF object.
.Pp
Argument
.Ar data
is an
.Vt Elf_Data
descriptor associated with a section of type
.Dv SHT_REL .
Argument
.Ar ndx
is the index of the entry being retrieved or updated.
The class-independent
.Vt GElf_Rel
structure is described in
.Xr gelf 3 .
.Pp
Function
.Fn gelf_getrel
retrieves the class-dependent entry at index
.Ar ndx
in data buffer
.Ar data
and copies it to the destination pointed to by argument
.Ar rel
after translation to class-independent form.
.Pp
Function
.Fn gelf_update_rel
converts the class-independent entry pointed to
by argument
.Ar rel
to class-dependent form, and writes it to the entry at index
.Ar ndx
in the data buffer described by argument
.Ar data .
Function
.Fn gelf_update_rel
signals an error if any of the values in the class-independent
representation exceeds the representable limits of the target
type.
.Sh RETURN VALUES
Function
.Fn gelf_getrel
returns the value of argument
.Ar rel
if successful, or NULL in case of an error.
Function
.Fn gelf_update_rel
returns a non-zero value if successful, or zero in case of an error.
.Sh ERRORS
These functions may fail with the following errors:
.Bl -tag -width "[ELF_E_RESOURCE]"
.It Bq Er ELF_E_ARGUMENT
Arguments
.Ar data
or
.Ar rel
were NULL.
.It Bq Er ELF_E_ARGUMENT
Argument
.Ar ndx
was less than zero or larger than the number of entries in the data
descriptor.
.It Bq Er ELF_E_ARGUMENT
Data descriptor
.Ar data
was not associated with a section of type
.Dv SHT_REL .
.It Bq Er ELF_E_RANGE
A value was not representable in the target type.
.It Bq Er ELF_E_VERSION
The
.Vt Elf_Data
descriptor denoted by argument
.Ar data
is associated with an ELF object with an unsupported version.
.El
.Sh SEE ALSO
.Xr elf 3 ,
.Xr elf_getdata 3 ,
.Xr elf_getscn 3 ,
.Xr gelf 3