.\" Copyright (c) 2010 Kai Wang
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.\" $Id: dwarf_attr.3 2072 2011-10-27 03:26:49Z jkoshy $
.\"
.Dd April 8, 2010
.Os
.Dt DWARF_ATTR 3
.Sh NAME
.Nm dwarf_attr
.Nd retrieve an attribute descriptor associated with a DWARF debugging information entry
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_attr
.Fa "Dwarf_Die die"
.Fa "Dwarf_Half attr"
.Fa "Dwarf_Attribute *atp"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_attr
retrieves the attribute descriptor for an attribute associated
with the DWARF debugging information entry descriptor in
argument
.Ar die .
.Pp
DWARF attribute descriptors are represented by value of the opaque
type
.Vt Dwarf_Attribute ,
see
.Xr dwarf 3 .
.Pp
Argument
.Ar attr
names the desired DWARF attribute.
Legal values for argument
.Ar attr
are those denoted by the
.Dv DW_AT_*
constants in the DWARF specification.
.Pp
Argument
.Ar atp
points to a location into which the returned attribute descriptor
will be written.
The returned descriptor may then be passed to the form query functions in the
.Xr dwarf 3
API set to access the data associated with the attribute.
.Pp
If argument
.Ar err
is non-NULL, it will be used to return an error descriptor in case
of an error.
.Sh RETURN VALUES
Function
.Fn dwarf_attr
returns
.Dv DW_DLV_OK on success.
.Pp
If the debugging information entry descriptor denoted by argument
.Ar die
does not contain the named attribute, the function returns
.Dv DW_DLV_NO_ENTRY
and sets argument
.Ar err .
For other errors, it returns
.Dv DW_DLV_ERROR
and sets argument
.Ar err .
.Sh ERRORS
Function
.Fn dwarf_attr
can fail with the following errors:
.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
.It Bq Er DW_DLE_ARGUMENT
Either of arguments
.Ar die
or
.Ar atp
was NULL.
.It Bq Er DW_DLE_NO_ENTRY
Argument
.Ar die
had no attribute corresponding to the value
in argument
.Ar attr .
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_attrlist 3 ,
.Xr dwarf_hasattr 3 ,
.Xr dwarf_hasform 3 ,
.Xr dwarf_whatattr 3 ,
.Xr dwarf_whatform 3