An incomplete attempt at enumerating DW_TAG_variable from DWARF data in ELF using libdw.

failed_using_dwarf-1.c

#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <elfutils/libdwelf.h>
#include <dwarf.h>

/*	
Bottom part of `objdump -Wi t3.o´ is:

	<1><d5>: Abbrev Number: 9 (DW_TAG_variable)
		<d6>   DW_AT_name        : (indirect string, offset: 0x15e): stuff
		<da>   DW_AT_decl_file   : 2
		<db>   DW_AT_decl_line   : 3
		<dc>   DW_AT_decl_column : 5
		<dd>   DW_AT_type        : <0x47>
		<e1>   DW_AT_external    : 1
		<e1>   DW_AT_location    : 9 byte block: 3 0 0 0 0 0 0 0 0 	(DW_OP_addr: 0)
	<1><eb>: Abbrev Number: 9 (DW_TAG_variable)
		<ec>   DW_AT_name        : (indirect string, offset: 0xc0): test_var
		<f0>   DW_AT_decl_file   : 2
		<f1>   DW_AT_decl_line   : 4
		<f2>   DW_AT_decl_column : 16
		<f3>   DW_AT_type        : <0x76>
		<f7>   DW_AT_external    : 1
		<f7>   DW_AT_location    : 9 byte block: 3 20 0 0 0 0 0 0 0 	(DW_OP_addr: 20)
	<1><101>: Abbrev Number: 0

	Using dwarf_getstring with the offsets 0x15e and 0xc0 I do get the DW_AT_name for the two DW_TAG_variable
	But I am unable to figure out how to get those offsets from the attributes when iterating through the DIEs.
	I am also unsure that I am actually iterating through them but I do hit DW_TAG_variable twice which is correct
	but I am unable to verify I am not getting the same data twice.

*/

int main(void) {
	int fd = open("t3.o", 0);

	Dwarf* dbgdata = dwarf_begin(fd, DWARF_C_READ);
	if (!dbgdata) {
		int eno = dwarf_errno();
		printf("Failed to load dwarf %i - %s\n", eno, dwarf_errmsg(eno));

	} else {

		Dwarf_Off off = 0;
		size_t cuhl;
		Dwarf_Off noff;

		//Go through CU (compilation units?) (one found)
		while (dwarf_nextcu (dbgdata, off, &noff, &cuhl, NULL, NULL, NULL) == 0) {

			Dwarf_Die die_mem;
			Dwarf_Die *die = dwarf_offdie (dbgdata, off + cuhl, &die_mem);

			Dwarf_Die iter_mem;
			Dwarf_Die *iter = &iter_mem;
			dwarf_child (die, &iter_mem);

			//Go through children in top DIE of the CU (or at least so I think)
			while (1) {

				if (dwarf_tag (iter) == DW_TAG_variable) {

					Dwarf_Attribute atr_mem;
					Dwarf_Attribute* atr = &atr_mem;
					
					if (dwarf_attr(iter, DW_AT_name, &atr_mem) == 0) {
						printf("Failed to atr\n");
					} else {
						printf("We have the attr but.. how do we get the offset in .debug_str section for DW_AT_name of this DW_TAG_variable? \n");	
					}
				}

				if (dwarf_siblingof (iter, &iter_mem) != 0) {
					break;
				}
			}
				
			off = noff;
		}

		dwarf_end(dbgdata);
	}

	close(fd);
	return 0;
}