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.\" Copyright (c) 2010 Kai Wang
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $Id: dwarf_attr.3 3093 2014-09-02 22:09:40Z kaiwang27 $
.\"
.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_attroffset 3 ,
.Xr dwarf_hasattr 3 ,
.Xr dwarf_hasform 3 ,
.Xr dwarf_whatattr 3 ,
.Xr dwarf_whatform 3
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