DWARF_PRODUCER_INIT(3)

DWARF_PRODUCER_INIT(3) 🌈

okay bestie, this page is from the Library Functions Manual and it's all about allocating a DWARF producer descriptor. It's giving big libdwarf energy, and we're gonna keep every single detail while making it make sense 💅

💖 NAME 💖

dwarf_producer_init, dwarf_producer_init_b — allocate a DWARF producer descriptor

📚 LIBRARY 📚

DWARF Access Library (libdwarf, -ldwarf) — literally the library and linker flag, bestie ✨

🪄 SYNOPSIS 🪄

#include <libdwarf.h>

Dwarf_P_Debug
dwarf_producer_init(Dwarf_Unsigned flags, Dwarf_Callback_Func func,
    Dwarf_Handler errhand, Dwarf_Ptr errarg, Dwarf_Error *err);

Dwarf_P_Debug
dwarf_producer_init_b(Dwarf_Unsigned flags, Dwarf_Callback_Func_b func,
    Dwarf_Handler errhand, Dwarf_Ptr errarg, Dwarf_Error *error);

🌸 DESCRIPTION 🌸

These functions allocate and return a Dwarf_P_Debug descriptor representing a DWARF producer instance. Slay.

The argument errhand should contain the address of a function to be called in case of an error. If this argument is NULL, the default error handling scheme is used, see dwarf(3).

The argument errarg will be passed to the error handler function when it is invoked.

The argument err references a memory location that would hold a Dwarf_Error descriptor in case of an error.

The argument flags specifies additional characteristics of the DWARF producer instance. The following flags are recognized:

• DW_DLC_ISA_IA64 — (Deprecated) the target instruction set architecture is IA64. This flag is deprecated. Application code should use the dwarf_producer_set_isa(3) function to specify target instruction set architecture. 🫠
• DW_DLC_ISA_MIPS — (Deprecated) the target instruction set architecture is MIPS. This flag is deprecated. Application code should use the dwarf_producer_set_isa(3) function to specify target instruction set architecture. 🫠
• DW_DLC_SIZE_32 — (Default) the target address size is 32-bit.
• DW_DLC_SIZE_64 — the target address size is 64-bit.
• DW_DLC_STREAM_RELOCATIONS — (Default) generate stream relocations.
• DW_DLC_SYMBOLIC_RELOCATIONS — generate symbolic relocations.
• DW_DLC_TARGET_BIGENDIAN — the target is big endian.
• DW_DLC_TARGET_LITTLEENDIAN — the target is little endian.
• DW_DLC_WRITE — (Required) permit writing of DWARF information. Don't skip this one, bestie, it's literally required 💀

The following flags are mutually exclusive. Pick one from each pair, no chaotic combos:

• Flags DW_DLC_ISA_IA64 and DW_DLC_ISA_MIPS.
• Flags DW_DLC_SIZE_32 and DW_DLC_SIZE_64.
• Flags DW_DLC_STREAM_RELOCATIONS and DW_DLC_SYMBOLIC_RELOCATIONS.
• Flags DW_DLC_TARGET_BIGENDIAN and DW_DLC_TARGET_LITTLEENDIAN.

If neither of the flags DW_DLC_TARGET_BIGENDIAN and DW_DLC_TARGET_LITTLEENDIAN is set, the target's endianness is assumed to be the same as the host's endianness.

Argument func should point to an application-provided callback function of type Dwarf_Callback_Func_b. The type Dwarf_Callback_Func_b is defined in the header file <libdwarf.h> as:

typedef int (*Dwarf_Callback_Func_b)(char *name, int size,
    Dwarf_Unsigned type, Dwarf_Unsigned flags, Dwarf_Unsigned link,
    Dwarf_Unsigned info, Dwarf_Unsigned *index, int *error);

This function is called by the DWARF Access Library (libdwarf, -ldwarf) once for each section in the object file that the library needs to create. The arguments to this callback function specify the values in the ELF section header for the section being created:

• name — the name of the section being created.
• size — the sh_size value in the section header.
• type — the sh_type value in the section header.
• flags — the sh_flags value in the section header.
• link — the sh_link value in the section header.
• info — the sh_info value in the section header.

On success, the callback function should return the section index value of the created section, and set the location pointed to by argument index to the symbol table index of the symbol that associated with the newly created section. This symbol table index will be used in relocation entries referring to the created section. Iconic behavior ✨

In case of failure, the callback function should return -1 and set the location pointed to by argument error to an application-defined error code. This application returned error code is currently ignored by the library.

⚠️ Deprecated alert, bestie: function dwarf_producer_init() is deprecated. Function dwarf_producer_init() is identical to function dwarf_producer_init_b() except that the callback function it expects can not properly handle arbitrary section symbol index values. That's the tea ☕

🧹 Memory Management 🧹

The Dwarf_P_Debug instance returned by these functions should be freed using the function dwarf_producer_finish(). Clean up after yourself, periodt 💅

🎁 RETURN VALUES 🎁

On success, these functions return the created DWARF producer descriptor. In case of an error, they return DW_DLV_BADADDR and set the argument err.

🧪 EXAMPLES 🧪

To initialize a Dwarf_P_Debug instance for a MIPS32 big endian object, use:

             Dwarf_P_Debug dbg;
             Dwarf_Unsigned flags;
             Dwarf_Error de;

             /* ... assume cb_func points to the callback function ... */

             flags = DW_DLC_WRITE | DW_DLC_SIZE_32 | DW_DLC_ISA_MIPS |
                 DW_DLC_STREAM_RELOCATIONS | DW_DLC_TARGET_BIGENDIAN;
             if ((dbg = dwarf_producer_init(flags, cb_func, NULL, NULL, &de)) ==
                 DW_DLV_BADADDR)
                     warnx("dwarf_producer_init failed: %s", dwarf_errmsg(-1));

💀 ERRORS 💀

These functions can fail with:

• [DW_DLE_ARGUMENT] — argument func was NULL. 😭
• [DW_DLE_ARGUMENT] — the flag DW_DLC_WRITE was not set in argument flags.
• [DW_DLE_ARGUMENT] — the flags DW_DLC_SIZE_32 and DW_DLC_SIZE_64 were both set in argument flags.
• [DW_DLE_ARGUMENT] — the flags DW_DLC_ISA_IA64 and DW_DLC_ISA_MIPS were both set in argument flags.
• [DW_DLE_ARGUMENT] — the flags DW_DLC_TARGET_BIGENDIAN and DW_DLC_TARGET_LITTLEENDIAN were both set in argument flags.
• [DW_DLE_ARGUMENT] — the flags DW_DLC_STREAM_RELOCATIONS and DW_DLC_SYMBOLIC_RELOCATIONS were both set in argument flags.
• [DW_DLE_MEMORY] — an out of memory condition was encountered.

👀 SEE ALSO 👀

dwarf(3), dwarf_errmsg(3), dwarf_producer_finish(3), dwarf_producer_set_isa(3), dwarf_transform_to_disk_form(3)

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xoxo, from Debian 💖 — August 20, 2011 🫶