DWARF_ADD_LINE_ENTRY(3)

💖 dwarf_add_line_entry(3) 💖

okay so this page is from the Library Functions Manual, and it’s literally all about adding line-number info to a DWARF producer instance. very niche, very iconic, no cap 💅

🌸 NAME 🌸

dwarf_add_line_entry — add a line number information entry to a producer instance.

🧚 LIBRARY 🧚

DWARF Access Library (libdwarf, -ldwarf) — yes bestie, that’s the one you link against 🫶

✨ SYNOPSIS ✨

#include <libdwarf.h>

Dwarf_Unsigned
dwarf_add_line_entry(Dwarf_P_Debug dbg, Dwarf_Unsigned filendx,
    Dwarf_Addr off, Dwarf_Unsigned lineno, Dwarf_Signed column,
    Dwarf_Bool is_stmt, Dwarf_Bool basic_block, Dwarf_Error *err);

🦋 DESCRIPTION 🦋

Function dwarf_add_line_entry() adds a line number information entry to a DWARF producer instance. main character behavior, honestly ✨

• dbg — should reference a DWARF producer instance allocated using dwarf_producer_init(3) or dwarf_producer_init_b(3).
• filendx — specifies the index of the source file that contains the source line in question. Valid source file indices are those returned by the function dwarf_add_file_decl(3).
• off — specifies a relocatable program address. The ELF symbol to be used for relocation is set by a prior call to the function dwarf_lne_set_address(3).
• lineno — specifies the line number of the source line.
• column — specifies the column number within the source line.
• is_stmt — if set to true, it indicates that the instruction at the address specified by argument off is a recommended breakpoint location, i.e., the first instruction in the instruction sequence generated by the source line.
• basic_block — if set to true, it indicates that the instruction at the address specified by argument off is the first instruction of a basic block.
• err — if not NULL, it will be used to store error information in case of an error.

bestie, notice how off is relocatable and the ELF relocation symbol comes from a previous dwarf_lne_set_address(3) call. that setup is not optional in the vibe check 😌

🎀 RETURN VALUES 🎀

On success, function dwarf_add_line_entry() returns DW_DLV_OK. In case of an error, function dwarf_add_line_entry() returns DW_DLV_NOCOUNT and sets the argument err.

🔥 EXAMPLES 🔥

To add line number information to the producer instance, use:

Dwarf_P_Debug dbg;
Dwarf_Error de;
Dwarf_Unsigned dir, filendx;

/* ... assume dbg refers to a DWARF producer instance ... */

dir = dwarf_add_directory_decl(dbg, "/home/foo", &de);
if (dir == DW_DLV_NOCOUNT)
        errx(EXIT_FAILURE, "dwarf_add_directory_decl failed: %s",
            dwarf_errmsg(-1));

filendx = dwarf_add_file_decl(dbg, "bar.c", dir, 0, 1234, &de);
if (filendx == DW_DLV_NOCOUNT)
        errx(EXIT_FAILURE, "dwarf_add_file_decl failed: %s",
            dwarf_errmsg(-1));

if (dwarf_lne_set_address(dbg, 0x4012b0, 12, &de) != DW_DLV_OK)
        errx(EXIT_FAILURE, "dwarf_lne_set_address failed: %s",
            dwarf_errmsg(-1));

if (dwarf_add_line_entry(dbg, filendx, 10, 258, 0, 1, 1, &de) !=
    DW_DLV_OK)
        errx(EXIT_FAILURE, "dwarf_add_line_entry failed: %s",
            dwarf_errmsg(-1));

👑 ERRORS 👑

Function dwarf_add_line_entry() can fail with:

• [DW_DLE_ARGUMENT] — Argument dbg was NULL.
• [DW_DLE_ARGUMENT] — The function dwarf_lne_set_address(3) was not called before calling this function.
• [DW_DLE_MEMORY] — An out of memory condition was encountered during the execution of the function.

lowkey important: if you forgot dwarf_lne_set_address(3) first, this function is gonna hit you with [DW_DLE_ARGUMENT]. not me warning you bestie 🙈

🌈 SEE ALSO 🌈

dwarf(3), dwarf_add_directory_decl(3), dwarf_add_file_decl(3), dwarf_lne_end_sequence(3), dwarf_lne_set_address(3), dwarf_producer_init(3), dwarf_producer_init_b(3).

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and that’s the whole page, bestie 🫶 this one’s source/version is Debian, dated June 30, 2013 — slay and goodbye ✨💅