DWARF_FINISH(3)

✨ DWARF_FINISH(3) ✨

okay so bestie, real talk: this is a page from the Library Functions Manual and it's all about cleanup duty 💅 — freeing stuff you allocated. and the header literally says DWARF_FINISH(3), so, like, you're in the right place 🎀

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💖 NAME 💖

dwarf_finish, dwarf_object_finish — free resources associated with a debug descriptor

like, the goodbye functions. the "ok we're done here" functions. the closing the tab of libdwarf 🫶

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🦋 LIBRARY 🦋

DWARF Access Library (libdwarf, -ldwarf)

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🌸 SYNOPSIS 🌸

#include <libdwarf.h>

int
dwarf_finish(Dwarf_Debug dbg, Dwarf_Error *err);

int
dwarf_object_finish(Dwarf_Debug dbg, Dwarf_Error *err);

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🌈 DESCRIPTION 🌈

so. dwarf_finish() and dwarf_object_finish() are the functions you call to release the resources associated with a debug descriptor — and no cap, the descriptor has to be one that a prior call to dwarf_init(3) and dwarf_object_init(3) (respectively!) handed you ✨. so dwarf_finish() pairs with dwarf_init(3), and dwarf_object_finish() pairs with dwarf_object_init(3). keep the matching straight, iykyk 💖

the argument dbg is a valid Dwarf_Debug instance. the argument err is where error info gets recorded in case of an error 🍓

⚠️ girl. listen. after a call to dwarf_finish() or dwarf_object_finish(), the argument dbg will be invalid and should not be used further. like, it's gone, it's toast, do not touch it, that's undefined-behaviour territory and we don't go there 💀

and here's the part that lowkey trips everyone up: for Dwarf_Debug descriptors opened using dwarf_init(3), the application would need to explicitly release the Elf instance associated with the descriptor — by first retrieving the instance using dwarf_get_elf(3) and then closing it using elf_end(3). so it's a two-step. libdwarf doesn't do the elf part for you, that one's on you bestie 😭

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👑 RETURN VALUES 👑

these functions return DW_DLV_OK if successful 🌟. in case of an error, they return DW_DLV_ERROR and record additional information in the argument err.

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💜 EXAMPLES 💜

to deallocate a Dwarf_Debug instance allocated using dwarf_elf_init(3), use:

Dwarf_Debug dbg;
Dwarf_Error de;

if (dwarf_finish(dbg, &de) != DW_DLV_OK)
        errx(EXIT_FAILURE, "dwarf_finish: %s", dwarf_errmsg(de));

to deallocate a Dwarf_Debug instance allocated using dwarf_object_init(3), use:

Dwarf_Debug dbg;
Dwarf_Error de;

if (dwarf_object_finish(dbg, &de) != DW_DLV_OK)
        errx(EXIT_FAILURE, "dwarf_object_finish: %s",
            dwarf_errmsg(de));

to deallocate a Dwarf_Debug instance allocated using dwarf_init(3), use:

Dwarf_Debug dbg;
Dward_Error de;
Elf *e;

if (dwarf_get_elf(dbg, &e, &de) != DW_DLV_OK)
        errx(EXIT_FAILURE, "dwarf_get_elf: %s", dwarf_errmsg(&de));

if (dwarf_finish(dbg, &de) != DW_DLV_OK)
        errx(EXIT_FAILURE, "dwarf_finish: %s", dwarf_errmsg(de));

(void) elf_end(e);

🙈 and yes, that third example literally says Dward_Error de; in the original — we're keeping it verbatim because the one rule is don't touch the code. reproduce it as-is and let the compiler vibe check it for you 💀

see how the dwarf_init(3) one is the long one? that's the elf_end(e) situation from the DESCRIPTION. grab the Elf with dwarf_get_elf(3), finish the dwarf thing, then elf_end(3) it. two funerals. periodt 🎀

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🌟 SEE ALSO 🌟

dwarf_elf_init(3), dwarf_get_elf(3), dwarf_init(3), dwarf_object_init(3), elf_end(3)

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and that's the whole page, bestie, you ate that 🫶✨ this one's from Debian, dated November 9, 2011 — vintage icon behaviour honestly 👑🌸 go free your descriptors responsibly 💖