DWARF_GET_RANGES(3) | Library Functions Manual | DWARF_GET_RANGES(3)

# NAME

`dwarf_get_ranges` —
retrieve non-contiguous address ranges

# LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

# SYNOPSIS

`#include <libdwarf.h>`

int
`dwarf_get_ranges`(Dwarf_Debug dbg, Dwarf_Off offset, Dwarf_Ranges **ranges, Dwarf_Signed *cnt, Dwarf_Unsigned *byte_cnt, Dwarf_Error *err);

int
`dwarf_get_ranges_a`(Dwarf_Debug dbg, Dwarf_Off offset, Dwarf_Die die, Dwarf_Ranges **ranges, Dwarf_Signed *cnt, Dwarf_Unsigned *byte_cnt, Dwarf_Error *err);

# DESCRIPTION

Function `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 Dwarf_Ranges, with each Dwarf_Ranges descriptor describing one address range entry.

Argument dbg should reference a DWARF debug context allocated using dwarf_init(3).

Argument offset is an offset, relative to the “.debug_ranges” section, to the start of the desired list of address ranges. The offset of an address ranges list is indicated by the `DW_AT_ranges` attribute of a debugging information entry.

Argument die (function `dwarf_get_ranges_a`() only) is ignored in this implementation; see the section Compatibility Notes below.

Argument ranges should point to a location that will be set to a pointer to an array of Dwarf_Ranges descriptors.

Argument cnt should point to a location that will be set to the number of entries returned. If argument byte_cnt is not NULL, it will be set to the number of bytes occupied by the returned entries in the “.debug_ranges” section.

If argument err is not NULL, it will be used to store error information in case of an error.

Dwarf_Ranges descriptors are defined in the header file `<libdwarf.h>`, and consists of the following fields:

dwr_addr1
  The first address offset, whose meaning depends on the type of the entry.
dwr_addr2
  The second address offset, whose meaning depends on the type of the entry.
dwr_type
  The type of this address range entry:
  `DW_RANGES_ENTRY`
    A range list entry. For this type of entry, the fields dwr_addr1 and dwr_addr2 hold the beginning and ending offsets of the address range, respectively.
  `DW_RANGES_ADDRESS_SELECTION`
    A base address selection entry. For this type of entry, the field dwr_addr1 is the value of the largest representable address offset, and dwr_addr2 is a base address for the beginning and ending address offsets of subsequent address range entries in the list.
  `DW_RANGES_END`
    An end of list mark. Both dwr_addr1 and dwr_addr2 are set to 0.

## Memory Management

The memory area used for the array of Dwarf_Ranges descriptors returned in argument ranges is owned by the DWARF Access Library (libdwarf, -ldwarf). The application should not attempt to directly free this pointer. Portable code should instead use `dwarf_ranges_dealloc`() to indicate that the memory may be freed.

# COMPATIBILITY

Function `dwarf_get_ranges_a`() is identical to `dwarf_get_ranges`(), except that it requires one additional argument die denoting the debugging information entry associated with the address range list. In this implementation of the DWARF Access Library (libdwarf, -ldwarf), the argument die is ignored, and function `dwarf_get_ranges_a`() is only provided for compatibility with other implementations of the DWARF(3) API.

# RETURN VALUES

These functions return `DW_DLV_OK` when they succeed. They return `DW_DLV_NO_ENTRY` if there is no address range list at the specified offset offset. In case of an error, they return `DW_DLV_ERROR` and set the argument err.

# ERRORS

These function can fail with:

[`DW_DLE_ARGUMENT`]
  One of the arguments dbg, ranges or cnt was NULL.
[`DW_DLE_NO_ENTRY`]
  There is no address range list at the specified offset offset.

# EXAMPLE

To retrieve the address range list associated with a debugging information entry, use:

    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 ..
    			 */
    		}
    	}
    }

# SEE ALSO

dwarf(3), dwarf_ranges_dealloc(3)

November 9, 2011 | NetBSD 9.2