NAME

dwarf_loclist, dwarf_loclist_n — retrieve DWARF location expression information

LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS

#include <libdwarf.h>

int
dwarf_loclist(Dwarf_Attribute at, Dwarf_Locdesc **llbuf, Dwarf_Signed *listlen, Dwarf_Error *error);

int
dwarf_loclist_n(Dwarf_Attribute at, Dwarf_Locdesc ***llbuf, Dwarf_Signed *listlen, Dwarf_Error *error);

DESCRIPTION

These functions retrieve the location expressions associated with a DWARF attribute.

Note: function dwarf_loclist() is deprecated. New application code should instead use function dwarf_loclist_n()

Function dwarf_loclist_n() retrieves the list of location expressions associated with a DWARF attribute. Argument at should reference a valid DWARF attribute. Argument llbuf should point to a location which will hold a returned array of pointers to Dwarf_Locdesc descriptors. Argument listlen should point to a location which will be set to the number of elements contained in the returned array. If argument err is not NULL, it will be used to store error information in case of an error.

Function dwarf_loclist() retrieves the first location expression associated with an attribute. Argument at should reference a valid DWARF attribute. Argument llbuf should point to a location which will hold the returned pointer to a Dwarf_Locdesc descriptor. Argument listlen should point to a location which will be always set to 1. If argument err is not NULL, it will be used to store error information in case of an error.

Dwarf_Locdesc descriptors are defined in the header file <libdwarf.h>, and consist of following fields:

Each Dwarf_Loc descriptor represents one operation of a location expression. These descriptors are defined in the header file <libdwarf.h>, and consist of following fields:

Memory Management

The memory area used for the descriptor array returned in argument llbuf is allocated by the DWARF Access Library (libdwarf, -ldwarf). When the descriptor array is no longer needed, application code should use function dwarf_dealloc(3) to free the memory area in the following manner:

First, the ld_s field of each Dwarf_Locdesc descriptor should be deallocated using the allocation type DW_DLA_LOC_BLOCK.
Then, the application should free each Dwarf_Locdesc descriptor using the allocation type DW_DLA_LOCDESC.
Finally, the llbuf pointer should be deallocated using the allocation type DW_DLA_LIST.

RETURN VALUES

On success, these functions returns DW_DLV_OK. In case of an error, they return DW_DLV_ERROR and set the argument err.

ERRORS

These functions can fail with:

EXAMPLE

To retrieve the location list associated with an attribute, use:

Dwarf_Attribute at; 
Dwarf_Locdesc **llbuf; 
Dwarf_Signed lcnt; 
Dwarf_Loc *lr; 
Dwarf_Error de; 
int i; 
 
if (dwarf_loclist_n(at, &llbuf, &lcnt, &de) != DW_DLV_OK) 
	errx(EXIT_FAILURE, "dwarf_loclist_n failed: %s", 
	    dwarf_errmsg(de)); 
 
for (i = 0; i < lcnt; i++) { 
	/* ... Use llbuf[i] ... */ 
	for (j = 0; (Dwarf_Half) j < llbuf[i]->ld_cents; j++) { 
		lr = &llbuf[i]->ld_s[j]; 
		/* ... Use each Dwarf_Loc descriptor ... */ 
	} 
	dwarf_dealloc(dbg, llbuf[i]->ld_s, DW_DLA_LOC_BLOCK); 
	dwarf_dealloc(dbg, llbuf[i], DW_DLA_LOCDESC); 
} 
dwarf_dealloc(dbg, llbuf, DW_DLA_LIST);

Manual browser: dwarf_loclist_n(3)