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.\" Copyright (c) 2011 Kai Wang
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.\" Id: dwarf_get_ranges.3 2122 2011-11-09 15:35:14Z jkoshy
.\"
.Dd November 9, 2011
.Os
.Dt DWARF_GET_RANGES 3
.Sh NAME
.Nm dwarf_get_ranges
.Nd retrieve non-contiguous address ranges
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_get_ranges
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Off offset"
.Fa "Dwarf_Ranges **ranges"
.Fa "Dwarf_Signed *cnt"
.Fa "Dwarf_Unsigned *byte_cnt"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_get_ranges_a
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Off offset"
.Fa "Dwarf_Die die"
.Fa "Dwarf_Ranges **ranges"
.Fa "Dwarf_Signed *cnt"
.Fa "Dwarf_Unsigned *byte_cnt"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_get_ranges
retrieves information about the non-contiguous address ranges associated
with a DWARF debugging information entry.
Information about address ranges is returned as an array of
descriptors of type
.Vt Dwarf_Ranges ,
with each
.Vt Dwarf_Ranges
descriptor describing one address range entry.
.Pp
Argument
.Ar dbg
should reference a DWARF debug context allocated using
.Xr dwarf_init 3 .
.Pp
Argument
.Ar offset
is an offset, relative to the
.Dq ".debug_ranges"
section, to the start of the desired list of address ranges.
The offset of an address ranges list is indicated by the
.Dv DW_AT_ranges
attribute of a debugging information entry.
.Pp
Argument
.Ar die
(function
.Fn dwarf_get_ranges_a
only) is ignored in this implementation; see the section
.Sx "Compatibility Notes"
below.
.Pp
Argument
.Ar ranges
should point to a location that will be set to a pointer to an array
of
.Vt Dwarf_Ranges
descriptors.
.Pp
Argument
.Ar cnt
should point to a location that will be set to the number of entries
returned.
If argument
.Ar byte_cnt
is not NULL, it will be set to the number of bytes occupied by the
returned entries in the
.Dq ".debug_ranges"
section.
.Pp
If argument
.Ar err
is not NULL, it will be used to store error information in case
of an error.
.Pp
.Vt Dwarf_Ranges
descriptors are defined in the header file
.In libdwarf.h ,
and consists of the following fields:
.Bl -tag -width ".Va dwr_addr1"
.It Va dwr_addr1
The first address offset, whose meaning depends on the type of the
entry.
.It Va dwr_addr2
The second address offset, whose meaning depends on the type of the
entry.
.It Va dwr_type
The type of this address range entry:
.Bl -tag -width ".Dv DW_RANGES_ENTRY" -compact
.It Dv DW_RANGES_ENTRY
A range list entry.
For this type of entry, the fields
.Va dwr_addr1
and
.Va dwr_addr2
hold the beginning and ending offsets of the address range, respectively.
.It Dv DW_RANGES_ADDRESS_SELECTION
A base address selection entry.
For this type of entry, the field
.Va dwr_addr1
is the value of the largest representable address offset, and
.Va dwr_addr2
is a base address for the begining and ending address offsets of
subsequent address range entries in the list.
.It Dv DW_RANGES_END
An end of list mark.
Both
.Va dwr_addr1
and
.Va dwr_addr2
are set to 0.
.El
.El
.Ss Memory Management
The memory area used for the array of
.Vt Dwarf_Ranges
descriptors returned in argument
.Ar ranges
is owned by the
.Lb libdwarf .
The application should not attempt to directly free this pointer.
Portable code should instead use
.Fn dwarf_ranges_dealloc
to indicate that the memory may be freed.
.Sh COMPATIBILITY
Function
.Fn dwarf_get_ranges_a
is identical to
.Fn dwarf_get_ranges ,
except that it requires one additional argument
.Ar die
denoting the debugging information entry associated with
the address range list.
In this implementation of the
.Lb libdwarf ,
the argument
.Ar die
is ignored, and function
.Fn dwarf_get_ranges_a
is only provided for compatibility with other implementations of the
DWARF(3) API.
.Sh RETURN VALUES
These functions
return
.Dv DW_DLV_OK
when they succeed.
They return
.Dv DW_DLV_NO_ENTRY
if there is no address range list at the specified offset
.Ar offset .
In case of an error, they return
.Dv DW_DLV_ERROR
and set the argument
.Ar err .
.Sh ERRORS
These function can fail with:
.Bl -tag -width ".Bq Er DW_DLE_NO_ENTRY"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Ar dbg ,
.Ar ranges
or
.Ar cnt
was NULL.
.It Bq Er DW_DLE_NO_ENTRY
There is no address range list at the specified offset
.Ar offset .
.El
.Sh EXAMPLE
To retrieve the address range list associated with a debugging
information entry, use:
.Bd -literal -offset indent
Dwarf_Debug dbg;
Dwarf_Die die;
Dwarf_Error de;
Dwarf_Addr base;
Dwarf_Attribute *attr_list;
Dwarf_Ranges *ranges;
Dwarf_Signed cnt;
Dwarf_Unsigned off, attr_count, bytecnt;
int i, j;

if ((ret = dwarf_attrlist(die, &attr_list, &attr_count, &de)) !=
    DW_DLV_OK)
	errx(EXIT_FAILURE, "dwarf_attrlist failed: %s",
	    dwarf_errmsg(de));

for (i = 0; (Dwarf_Unsigned) i < attr_count; i++) {
	if (dwarf_whatattr(attr_list[i], &attr, &de) != DW_DLV_OK) {
		warnx("dwarf_whatattr failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (attr != DW_AT_ranges)
		continue;
	if (dwarf_formudata(attr_list[i], &off, &de) != DW_DLV_OK) {
		warnx("dwarf_formudata failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (dwarf_get_ranges(dbg, (Dwarf_Off) off, &ranges, &cnt,
	    &bytecnt, &de) != DW_DLV_OK)
		continue;
	for (j = 0; j < cnt; j++) {
		if (ranges[j].dwr_type == DW_RANGES_END)
			break;
		else if (ranges[j].dwr_type ==
		    DW_RANGES_ADDRESS_SELECTION)
			base = ranges[j].dwr_addr2;
		else {
			/*
			 * DW_RANGES_ENTRY entry.
			 * .. Use dwr_addr1 and dwr_addr2 ..
			 */
		}
	}
}
.Ed
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_ranges_dealloc 3