DWARF_GET_FDE_INFO_FOR_REG(3)

🦋 DWARF_GET_FDE_INFO_FOR_REG(3) 🦋

okay so this is the DWARF_GET_FDE_INFO_FOR_REG(3) page from the Library Functions Manual, and it's giving deep DWARF frame-table lore in the best way 💅✨

💖 NAME 💖

dwarf_get_fde_info_for_reg — retrieve register rule

🌈 LIBRARY 🌈

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

✨ SYNOPSIS ✨

#include <libdwarf.h>

int
dwarf_get_fde_info_for_reg(Dwarf_Fde fde, Dwarf_Half table_column,
    Dwarf_Addr pc, Dwarf_Signed *offset_relevant,
    Dwarf_Signed *register_num, Dwarf_Signed *offset,
    Dwarf_Addr *row_pc, Dwarf_Error *error);

📖 DESCRIPTION 📖

okay so dwarf_get_fde_info_for_reg() retrieves a register rule from the register rule table associated with a given FDE descriptor, given a program counter address and rule column number. It's literally going into the frame data and pulling out the rule you asked for 🔎

Argument fde should reference a valid DWARF FDE descriptor.

Argument table_column should hold the column number of the register rule desired.

Argument pc should hold the program counter address to be used to locate the desired register rule row.

On successful execution, dwarf_get_fde_info_for_reg() stores information about the register rule found into the locations pointed to by the arguments offset_relevant, register_num, offset and row_pc.

If there is an offset value associated with the register rule, the location pointed to by argument offset_relevant will be set to 1.

Argument register_num should point to a location which will hold the register number associated with the register rule.

Argument offset should point to a location which will be set to the offset value associated with the register rule, or to 0 if the register rule does not have an offset value.

Argument row_pc should point to a location which will be set to the lowest program counter address associated with the register rule found.

If argument err is not NULL, it will be used to return an error descriptor in case of an error. (And yes, the synopsis calls it error while the prose calls it err — tiny gremlin inconsistency, but that's what the page says 🙈)

⚠️ COMPATIBILITY ⚠️

bestie, listen: dwarf_get_fde_info_for_reg() is deprecated since it only supports DWARF2 frame sections. Applications should instead use function dwarf_get_fde_info_for_reg3(3) which supports both DWARF2 and DWARF3 frame sections. Use the newer one, no cap 💅

🔁 RETURN VALUES 🔁

Function dwarf_get_fde_info_for_reg() returns DW_DLV_OK when it succeeds. In case of an error, it returns DW_DLV_ERROR and sets the argument err.

💀 ERRORS 💀

Function dwarf_get_fde_info_for_reg() can fail with:

• [DW_DLE_ARGUMENT] — One of the arguments fde, offset_relevant, register_num, offset or row_pc was NULL.
• [DW_DLE_FRAME_TABLE_COL_BAD] — The column number provided in argument table_column was too large.
• [DW_DLE_PC_NOT_IN_FDE_RANGE] — The program counter value provided in argument pc did not fall in the range covered by argument fde.

👀 SEE ALSO 👀

dwarf(3), dwarf_get_fde_at_pc(3), dwarf_get_fde_info_for_all_regs(3), dwarf_get_fde_info_for_all_regs3(3), dwarf_get_fde_info_for_cfa_reg3(3), dwarf_get_fde_info_for_reg3(3), dwarf_get_fde_n(3), dwarf_set_frame_cfa_value(3), dwarf_set_frame_rule_initial_value(3), dwarf_set_frame_rule_table_size(3), dwarf_set_frame_same_value(3), dwarf_set_frame_undefined_value(3)

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🌸 that's the whole page, bestie — brought to you by Debian, dated June 4, 2011, and filed under DWARF_GET_FDE_INFO_FOR_REG(3). mwah 💋✨