.\" Copyright (c) 2010 Kai Wang
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.\" $Id: dwarf_next_cu_header.3 2074 2011-10-27 03:34:33Z jkoshy $
.\"
.Dd July 24, 2010
.Os
.Dt DWARF_NEXT_CU_HEADER 3
.Sh NAME
.Nm dwarf_next_cu_header ,
.Nm dwarf_next_cu_header_b
.Nd step through compilation units in a DWARF debug context
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_next_cu_header
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Unsigned *cu_length"
.Fa "Dwarf_Half *cu_version"
.Fa "Dwarf_Off *cu_abbrev_offset"
.Fa "Dwarf_Half *cu_pointer_size"
.Fa "Dwarf_Unsigned *cu_next_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_next_cu_header_b
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Unsigned *cu_length"
.Fa "Dwarf_Half *cu_version"
.Fa "Dwarf_Off *cu_abbrev_offset"
.Fa "Dwarf_Half *cu_pointer_size"
.Fa "Dwarf_Half *cu_offset_size"
.Fa "Dwarf_Half *cu_extension_size"
.Fa "Dwarf_Unsigned *cu_next_offset"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
These functions are used to step through compilation unit contexts
associated with a DWARF debug context, optionally returning information
about the unit.
.Pp
Function
.Fn dwarf_next_cu_header_b
is the API recommended for new application code.
Argument
.Ar dbg
should reference a DWARF debug context allocated using
.Xr dwarf_init 3 .
Argument
.Ar cu_length
should point to a location that will be set to the
length of the compilation unit.
Argument
.Ar cu_version
should point to a location that will be set to the
version number for the compilation unit.
Argument
.Ar cu_abbrev_offset
should point to a location that will be set to the
starting offset (in the
.Dq .debug_abbrev
section) of the set of debugging information entry abbreviations
associated with this compilation unit.
Argument
.Ar cu_pointer_size
should point to a location that will be set to the
size in bytes of an address for the machine architecture of the
underlying object being debugged.
Argument
.Ar cu_offset_size
should point to a location that will be set to the
size in bytes for a DWARF offset in the compilation unit.
Argument
.Ar cu_extension_size
is only needed for processing MIPS/IRIX objects that use
a non-standard DWARF format.
It should point to a location that will be set to 4 for normal
objects and to 0 for non-standard ones.
Argument
.Ar cu_next_offset
should point to a location that will be set to the
offset of the next compilation unit header in the
.Dq \&.debug_info
section.
Argument
.Ar err
should point to a location that will hold an error descriptor in case
of an error.
.Pp
Function
.Fn dwarf_next_cu_header
is less general than
.Fn dwarf_next_cu_header_b ,
and is deprecated for use by new application code.
Argument
.Ar dbg
should reference a DWARF debug context allocated using
.Xr dwarf_init 3 .
Argument
.Ar cu_length
should point to a location that will be set to the
length of the compilation unit.
Argument
.Ar cu_version
should point to a location that will be set to the
version number for the compilation unit.
Argument
.Ar cu_abbrev_offset
should point to a location that will be set to the
starting offset in the
.Dq .debug_abbrev
section of the set of debugging information entry abbreviations
associated with this compilation unit.
Argument
.Ar cu_pointer_size
should point to a location that will be set to the
size of an address in bytes for the machine architecture of the
underlying debugging object.
Argument
.Ar cu_next_offset
should point to a location that will be set to the
offset of the next compilation unit.
Argument
.Ar err
should point to a location that will hold an error descriptor in case
of an error.
.Pp
A value of NULL may be used for any of the arguments
.Ar cu_length ,
.Ar cu_version ,
.Ar cu_abbrev_offset ,
.Ar cu_pointer_size ,
.Ar cu_offset_size ,
.Ar cu_extension_size ,
.Ar cu_next_offset
and
.Ar err
if the caller is not interested in the respective value.
.Ss Iterating Through Compilation Units in a Debug Context
.Pp
The first call to functions
.Fn dwarf_next_cu_header_b
and
.Fn dwarf_next_cu_header
for a given debug context will return information about the first
compilation unit in the debug context.
Subsequent calls to these functions will iterate through the remaining
compilation units in the debug context.
On stepping past the last compilation unit in the debug context,
functions
.Fn dwarf_next_cu_header
and
.Fn dwarf_next_cu_header_b
return
.Dv DW_DLV_NO_ENTRY
and reset their internal state.
The next call to these functions will restart from the first compilation
unit in the debug context.
.Sh RETURN VALUES
On success, these functions return
.Dv DW_DLV_OK .
In case of an error, they return
.Dv DW_DLV_ERROR
and set argument
.Ar err .
When there are no more compilation units left to traverse, they return
.Dv DW_DLV_NO_ENTRY .
.Sh ERRORS
These functions can fail with the following error:
.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
.It Bq Er DW_DLE_ARGUMENT
Argument
.Va dbg
was NULL.
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_get_cu_die_offset_given_cu_header_offset 3 ,
.Xr dwarf_init 3 ,
.Xr dwarf_siblingof 3