.\" Copyright (c) 2006,2008 Joseph Koshy.  All rights reserved.
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.\" Id: gelf_getsym.3 189 2008-07-20 10:38:08Z jkoshy 
.\"
.Dd August 29, 2006
.Os
.Dt GELF_GETSYM 3
.Sh NAME
.Nm gelf_getsym ,
.Nm gelf_update_sym
.Nd read and update symbol information
.Sh LIBRARY
.Lb libelf
.Sh SYNOPSIS
.In gelf.h
.Ft "GElf_Sym *"
.Fn gelf_getsym "Elf_Data *data" "int ndx" "GElf_Sym *sym"
.Ft int
.Fn gelf_update_sym "Elf_Data *data" "int ndx" "GElf_Sym *sym"
.Sh DESCRIPTION
These convenience functions are used to retrieve and update class-dependent
.Vt Elf32_Sym
and
.Vt Elf64_Sym
structures in an ELF object.
.Pp
Argument
.Ar data
is an
.Vt Elf_Data
descriptor associated with a section of type
.Dv SHT_SYMTAB ,
.Dv SHT_DYNSYM
or
.Dv SHT_GNU_versym .
Argument
.Ar ndx
is the index of the symbol being retrieved or updated.
The class-independent
.Vt GElf_Sym
structure is described in
.Xr gelf 3 .
.Pp
Function
.Fn gelf_getsym
retrieves class-dependent symbol information at index
.Ar ndx
in data buffer
.Ar data
and copies it to the destination pointed to by argument
.Ar sym
after translation to class-independent form.
.Pp
Function
.Fn gelf_update_sym
converts the class-independent symbol information pointed to
by argument
.Ar sym
to class-dependent form, and writes it to the symbol entry at index
.Ar ndx
in the data buffer described by argument
.Ar data .
Function
.Fn gelf_update_sym
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_getsym
returns the value of argument
.Ar sym
if successful, or NULL in case of an error.
Function
.Fn gelf_update_sym
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 sym
were NULL.
.It Bq Er ELF_E_ARGUMENT
Argument
.Ar ndx
was less than zero or larger than the number of symbols in the data
descriptor.
.It Bq Er ELF_E_ARGUMENT
Data descriptor
.Ar data
was not associated with a section containing symbol information.
.It Bq Er ELF_E_RANGE
A value was not representable in the target type.
.El
.Sh SEE ALSO
.Xr elf 3 ,
.Xr elf_getdata 3 ,
.Xr elf_getscn 3 ,
.Xr gelf 3 ,
.Xr gelf_getsyminfo 3 ,
.Xr gelf_update_syminfo 3