OBJCOPY(1)

📦 version 2.47, in arch rolling

🎀 objcopy — copy and translate object files 🎀

okay so bestie, welcome to objcopy(1) from GNU Development Tools ✨ this is the icon, the main character, the one that copies your object files and translates them between formats. grab a strawberry drink 🍓 and let's get into it.

🌸 NAME 🌸

objcopy — copy and translate object files 💅

✨ SYNOPSIS ✨

objcopy [-F bfdname|--target=bfdname]
        [-I bfdname|--input-target=bfdname]
        [-O bfdname|--output-target=bfdname]
        [-B bfdarch|--binary-architecture=bfdarch]
        [-S|--strip-all]
        [-g|--strip-debug]
        [--strip-unneeded]
        [-K symbolname|--keep-symbol=symbolname]
        [--keep-file-symbols]
        [--keep-section-symbols]
        [-N symbolname|--strip-symbol=symbolname]
        [--strip-unneeded-symbol=symbolname]
        [-G symbolname|--keep-global-symbol=symbolname]
        [--localize-hidden]
        [-L symbolname|--localize-symbol=symbolname]
        [--globalize-symbol=symbolname]
        [--globalize-symbols=filename]
        [-W symbolname|--weaken-symbol=symbolname]
        [-w|--wildcard]
        [-x|--discard-all]
        [-X|--discard-locals]
        [-b byte|--byte=byte]
        [-i [breadth]|--interleave[=breadth]]
        [--interleave-width=width]
        [-j sectionpattern|--only-section=sectionpattern]
        [-R sectionpattern|--remove-section=sectionpattern]
        [--keep-section=sectionpattern]
        [--remove-relocations=sectionpattern]
        [--strip-section-headers]
        [-p|--preserve-dates]
        [-D|--enable-deterministic-archives]
        [-U|--disable-deterministic-archives]
        [--debugging]
        [--gap-fill=val]
        [--pad-to=address]
        [--set-start=val]
        [--adjust-start=incr]
        [--change-addresses=incr]
        [--change-section-address sectionpattern{=,+,-}val]
        [--change-section-lma sectionpattern{=,+,-}val]
        [--change-section-vma sectionpattern{=,+,-}val]
        [--change-warnings] [--no-change-warnings]
        [--set-section-flags sectionpattern=flags]
        [--set-section-alignment sectionpattern=align]
        [--add-section sectionname=filename]
        [--dump-section sectionname=filename]
        [--update-section sectionname=filename]
        [--rename-section oldname=newname[,flags]]
        [--long-section-names {enable,disable,keep}]
        [--change-leading-char] [--remove-leading-char]
        [--reverse-bytes=num]
        [--srec-len=ival] [--srec-forceS3]
        [--redefine-sym old=new]
        [--redefine-syms=filename]
        [--weaken]
        [--keep-symbols=filename]
        [--strip-symbols=filename]
        [--strip-unneeded-symbols=filename]
        [--keep-global-symbols=filename]
        [--localize-symbols=filename]
        [--weaken-symbols=filename]
        [--binary-symbol-prefixstring]
        [--add-symbol name=[section:]value[,flags]]
        [--alt-machine-code=index]
        [--prefix-symbols=string]
        [--prefix-sections=string]
        [--prefix-alloc-sections=string]
        [--add-gnu-debuglink=path-to-file]
        [--only-keep-debug]
        [--strip-dwo]
        [--extract-dwo]
        [--extract-symbol]
        [--writable-text]
        [--readonly-text]
        [--pure]
        [--impure]
        [--file-alignment=num]
        [--heap=reserve[,commit]]
        [--image-base=address]
        [--section-alignment=num]
        [--stack=reserve[,commit]]
        [--subsystem=which:major.minor]
        [--compress-debug-sections]
        [--decompress-debug-sections]
        [--elf-stt-common=val]
        [--merge-notes]
        [--no-merge-notes]
        [--verilog-data-width=val]
        [-v|--verbose]
        [-V|--version]
        [--help] [--info]
        infile [outfile]

💖 DESCRIPTION 💖

The GNU objcopy utility copies the contents of one object file into another. it literally uses the GNU BFD Library to read and write your object files, and it can write the destination in a different format from the source. absolute slay. the exact behavior is controlled by the command-line options, so it's giving customizable 💅

⚠️ heads up bestie: objcopy should be able to copy a fully linked file between any two formats. but copying a relocatable object file between any two formats may not work as expected. so don't come for her if that particular vibe check fails 😭

objcopy creates temporary files to do its translations and deletes them afterward 🧚 it uses BFD for all its translation work — it has access to all the formats described in BFD, so it can recognize most formats without being told explicitly. she just knows 💅

objcopy can be used to generate S-records by using an output target of srec (e.g., use -O srec). ✨

objcopy can also be used to generate a raw binary file by using an output target of binary (e.g., use -O binary). when objcopy generates a raw binary file, it will essentially produce a memory dump of the contents of the input object file. all symbols and relocation information will be discarded 🗑️ and the memory dump will start at the load address of the lowest section copied into the output file.

when generating an S-record or a raw binary file, it may be helpful to use -S to remove sections containing debugging information. in some cases -R will be useful to remove sections which contain information that is not needed by the binary file 🔥

🚨 Note — objcopy is not able to change the endianness of its input files. if the input format has an endianness (some formats do not), objcopy can only copy the inputs into file formats that have the same endianness or which have no endianness (e.g., srec). (however, see the --reverse-bytes option 👀)

🦋 OPTIONS 🦋

  • infile, outfile — the input and output files, respectively. if you don't specify outfile, objcopy creates a temporary file and destructively renames the result with the name of infile. (yes, destructively. bestie she's not asking permission 💀)

🌈 Target & format stuff 🌈

  • -I bfdname, --input-target=bfdname — treat the source file's object format as bfdname instead of trying to figure it out herself.
  • -O bfdname, --output-target=bfdname — write the output file using the object format bfdname. ✨
  • -F bfdname, --target=bfdname — use bfdname as the object format for both the input and the output file; i.e., simply transfer data from source to destination with no translation. no thoughts, just vibes 🫶
  • -B bfdarch, --binary-architecture=bfdarch — useful when transforming an architecture-less input file into an object file. in this case the output architecture can be set to bfdarch. this option will be ignored if the input file has a known bfdarch. you can access this binary data inside a program by referencing the special symbols that are created by the conversion process. those symbols are called _binary_objfile_start, _binary_objfile_end and _binary_objfile_size. e.g. you can transform a picture file into an object file and then access it in your code using these symbols 🖼️✨

🎀 Section-y things 🎀

  • -j sectionpattern, --only-section=sectionpattern — copy only the indicated sections from the input file to the output file. this option may be given more than once. note that using this option inappropriately may make the output file unusable 😬 wildcard characters are accepted in sectionpattern.

if the first character of sectionpattern is the exclamation point (!) then matching sections will not be copied, even if earlier use of --only-section on the same command line would otherwise copy it. for example:

          --only-section=.text.* --only-section=!.text.foo

will copy all sections matching .text.* but not the section .text.foo. (the original manpage wrote "sectinos" there and honestly? iconic typo, we're preserving the lore 💀)

  • -R sectionpattern, --remove-section=sectionpattern — remove any section matching sectionpattern from the output file. this option may be given more than once. note that using this option inappropriately may make the output file unusable 😭 wildcard characters are accepted in sectionpattern. using both the -j and -R options together results in undefined behaviour 🚨

if the first character of sectionpattern is the exclamation point (!) then matching sections will not be removed even if an earlier use of --remove-section on the same command line would otherwise remove it. for example:

          --remove-section=.text.* --remove-section=!.text.foo

will remove all sections matching the pattern .text.*, but will not remove the section .text.foo.

  • --keep-section=sectionpattern — when removing sections from the output file, keep sections that match sectionpattern. bestie said "not this one, she stays" 🫶
  • --remove-relocations=sectionpattern — remove non-dynamic relocations from the output file for any section matching sectionpattern. this option may be given more than once. note that using this option inappropriately may make the output file unusable, and attempting to remove a dynamic relocation section such as .rela.plt from an executable or shared library with --remove-relocations=.plt will not work 🚫 wildcard characters are accepted in sectionpattern. for example:
          --remove-relocations=.text.*

will remove the relocations for all sections matching the pattern .text.*.

if the first character of sectionpattern is the exclamation point (!) then matching sections will not have their relocation removed even if an earlier use of --remove-relocations on the same command line would otherwise cause the relocations to be removed. for example:

          --remove-relocations=.text.* --remove-relocations=!.text.foo

will remove all relocations for sections matching the pattern .text.*, but will not remove relocations for the section .text.foo.

  • --strip-section-headers — strip section header. this option is specific to ELF files. implies --strip-all and --merge-notes. 💅

💀 Stripping 💀

  • -S, --strip-all — do not copy relocation and symbol information from the source file. also deletes debug sections. gone, reduced to atoms ✨
  • -g, --strip-debug — do not copy debugging symbols or sections from the source file.
  • --strip-unneeded — remove all symbols that are not needed for relocation processing, in addition to debugging symbols and sections stripped by --strip-debug. lowkey thorough 💅

🧚 Symbol keeping & stripping 🧚

  • -K symbolname, --keep-symbol=symbolname — when stripping symbols, keep symbol symbolname even if it would normally be stripped. this option may be given more than once. protect her at all costs 🫶
  • -N symbolname, --strip-symbol=symbolname — do not copy symbol symbolname from the source file. this option may be given more than once.
  • --strip-unneeded-symbol=symbolname — do not copy symbol symbolname from the source file unless it is needed by a relocation. this option may be given more than once.
  • -G symbolname, --keep-global-symbol=*symbolname* — bestie, this one says only keep symbolname global 💅. Every other symbol gets made local to the file so it's not visible externally anymore. You can pass this more than once, no cap. ⚠️ Note: it cannot be used with --globalize-symbol or --globalize-symbols — they're literally beefing, don't put them in the same group chat.
  • --localize-hidden — in an ELF object, mark all symbols that have hidden or internal visibility as local. It stacks on top of the symbol-specific localization options like -L, so it's giving "yes, and" energy ✨.
  • -L symbolname, --localize-symbol=*symbolname* — takes a global or weak symbol called symbolname and makes it a local symbol so it's not visible externally 🙈. Can be given more than once. Note: unique symbols are not converted, periodt.
  • -W symbolname, --weaken-symbol=*symbolname* — makes symbolname weak 🫶. Also repeatable, because obviously.
  • --binary-symbol-prefix=*string* — when you're running it with --input-target=binary, this sets string as the base name for the symbols generated for the input file 🎀. Those symbols are:
<string>_start
<string>_end
<string>_size

By default, the binary input handler derives the prefix symbol name from a mangled version of the input file name plus the _binary prefix. This option lets you specify it explicitly instead — main character energy, you decide the name 💅.

  • --globalize-symbol=*symbolname* — gives symbolname global scoping so it's visible outside the file it's defined in 🌈. Repeatable! ⚠️ Note: cannot be used with -G or --keep-global-symbol. Same feud as above, iykyk.
  • -w, --wildcard — permits regular expressions in the symbolnames used in other command line options 🔥. The question mark (?), asterisk (*), backslash (\) and square brackets ([]) operators can be used anywhere in the symbol name. And plot twist: if the first character of the symbol name is an exclamation point (!), the sense of the switch gets reversed for that symbol. For example:
-w -W !foo -W fo*

would cause objcopy to weaken all symbols that start with "fo" except for the symbol "foo". Iconic behavior honestly.

  • -x, --discard-all — do not copy non-global symbols from the source file. That's it, that's the vibe 🗑️.
  • -X, --discard-locals — do not copy compiler-generated local symbols. (These usually start with L or ..) Bye bestie 👋
  • -b byte, --byte=*byte* — if interleaving has been enabled via the --interleave option, start the range of bytes to keep at the byteth byte 🦋. byte can be in the range from 0 to breadth-1, where breadth is the value given by the --interleave option.
  • -i [breadth], --interleave[=*breadth*] — only copy a range out of every breadth bytes. (Header data is not affected, don't worry 🎀.) Select which byte in the range begins the copy with the --byte option, and select the width of the range with the --interleave-width option.

This option is useful for creating files to program ROM, which is honestly kinda slay ✨. It's typically used with an "srec" output target. Note that objcopy will complain if you do not specify the --byte option as well 😭 — it's not being mean, it's being honest.

The default interleave breadth is 4, so with --byte set to 0, objcopy would copy the first byte out of every four bytes from the input to the output. Math ate, fr fr.

  • --interleave-width=*width* — when used with the --interleave option, copy width bytes at a time ⭐. The start of the range of bytes to be copied is set by the --byte option, and the extent of the range is set with the --interleave option.

The default value for this option is 1. The value of width plus the byte value set by the --byte option must not exceed the interleave breadth set by the --interleave option — that's a hard rule, no wiggle room 💀.

This option can be used to create images for two 16-bit flashes interleaved in a 32-bit bus by passing -b 0 -i 4 --interleave-width=2 and -b 2 -i 4 --interleave-width=2 to two objcopy commands. If the input was '12345678' then the outputs would be '1256' and '3478' respectively. Look at that, chef's kiss 👑.

  • -p, --preserve-dates — set the access and modification dates of the output file to be the same as those of the input file 🕰️.

This option also copies the date stored in a PE format file's header, unless the SOURCE_DATE_EPOCH environment variable is defined. If it is defined then this variable will be used as the date stored in the header, interpreted as the number of seconds since the Unix epoch. Very demure, very timestamped 💜.

  • -D, --enable-deterministic-archives — operate in deterministic mode 🌸. When copying archive members and writing the archive index, use zero for UIDs, GIDs, timestamps, and use consistent file modes for all files. Consistency is the moment.

If binutils was configured with --enable-deterministic-archives, then this mode is on by default. It can be disabled with the -U option, below 👇.

  • -U, --disable-deterministic-archives — do not operate in deterministic mode. This is the inverse of the -D option above: when copying archive members and writing the archive index, use their actual UID, GID, timestamp, and file mode values 🍓.

This is the default unless binutils was configured with --enable-deterministic-archives. Chaotic but valid, we respect it.

  • --debugging — convert debugging information, if possible 🧚. This is not the default because only certain debugging formats are supported, and the conversion process can be time consuming. Lowkey the lore drop, ngl.
  • --gap-fill val — fill gaps between sections with val 🎨. This operation applies to the load address (LMA) of the sections. It's done by increasing the size of the section with the lower address, and filling in the extra space created with val. Filling the void, literally.
  • --pad-to address — pad the output file up to the load address address 💅. This is done by increasing the size of the last section. The extra space is filled in with the value specified by --gap-fill (default zero). Default = 0, in case you were wondering 🫶.
  • --set-start val — set the start address (also known as the entry address) of the new file to val ⭐. Not all object file formats support setting the start address — some of them simply can't, and that's their journey 😔.
  • --change-start incr, --adjust-start incr — change the start address (also known as the entry address) by adding incr 🔥. Same disclaimer as above: not all object file formats support setting the start address.
  • --change-addresses incr, --adjust-vma incr — change the VMA and LMA addresses of all sections, as well as the start address, by adding incr 🌈. Some object file formats do not permit section addresses to be changed arbitrarily.
⚠️ Note that this does not relocate the sections. If the program expects sections to be loaded at a certain address, and this option is used to change the sections such that they are loaded at a different address, the program may fail. That's a real risk bestie, like actually.
  • --change-section-address sectionpattern{=,+,-}val, --adjust-section-vma sectionpattern{=,+,-}val — set or change both the VMA address and the LMA address of any section matching sectionpattern 🎯. If = is used, the section address is set to val. Otherwise, val is added to or subtracted from the section address. See the comments under --change-addresses above — they still apply, fr. If sectionpattern does not match any sections in the input file, a warning will be issued, unless --no-change-warnings is used.
  • --change-section-lma sectionpattern{=,+,-}val — set or change the LMA address of any sections matching sectionpattern 🦋. The LMA address is the address where the section will be loaded into memory at program load time. Normally this is the same as the VMA address, which is the address of the section at program run time, but on some systems — especially those where a program is held in ROM — the two can be different 👀.

If = is used, the section address is set to val. Otherwise, val is added to or subtracted from the section address. See the comments under --change-addresses above. If sectionpattern does not match any sections in the input file, a warning will be issued, unless --no-change-warnings is used.

  • --change-section-vma sectionpattern{=,+,-}val — set or change the VMA address of any section matching sectionpattern ✨. The VMA address is the address where the section will be located once the program has started executing. Normally this is the same as the LMA address, which is the address where the section will be loaded into memory, but on some systems — especially those where a program is held in ROM — the two can be different.

If = is used, the section address is set to val. Otherwise, val is added to or subtracted from the section address. See the comments under --change-addresses above. If sectionpattern does not match any sections in the input file, a warning will be issued, unless --no-change-warnings is used.

💀 Note: changing the VMA of sections in a fully linked binary can be dangerous since there may be code that expects the sections to be located at their old address. Genuinely, do not do this casually.
  • --change-warnings, --adjust-warnings — if --change-section-address or --change-section-lma or --change-section-vma is used, and the section pattern does not match any sections, issue a warning 📢. This is the default, so it's already the vibe unless you turn it off.
  • --no-change-warnings, --no-adjust-warnings — do not issue a warning if --change-section-address or --adjust-section-lma or --adjust-section-vma is used, even if the section pattern does not match any sections 🤫. Silence is golden, I guess.
  • --set-section-flags sectionpattern=flags — set the flags for any sections matching sectionpattern 🎀. The flags argument is a comma separated string of flag names. The recognized names are alloc, contents, load, noload, readonly, code, data, rom, exclude, share, debug, and large.

You can set the contents flag for a section which does not have contents, but it is not meaningful to clear the contents flag of a section which does have contents — just remove the section instead, bestie 💅. Not all flags are meaningful for all object file formats. In particular the share flag is only meaningful for COFF format files and not for ELF format files. The ELF x86-64 specific flag large corresponds to SHF_X86_64_LARGE. Slay, architecture-specific details.

  • --set-section-alignment sectionpattern=align — set the alignment for any sections matching sectionpattern 🦋. align specifies the alignment in bytes and must be a power of two, i.e. 1, 2, 4, 8.... Powers of two only, no exceptions, that's the rule 👑.
Tiny note before we keep rolling, bestie 🫶 — setting a section’s alignment does not magically line up its LMA or VMA addresses. If those need to change too, use --change-section-lma and/or --change-section-vma. Also lowkey warning: changing VMAs can cause problems in fully linked binaries where code expects section contents to be at their old address. 💀
  • --add-section sectionname=filename — adds a brand-new section called sectionname while copying. Its contents come from filename, and its size is the size of the file. This only works on file formats that support sections with arbitrary names. Note: you may need --set-section-flags to set the attributes of the newly created section. 💅
  • --dump-section sectionname=filename — drops the contents of section sectionname into filename, overwriting whatever was there before. It’s the inverse of --add-section. Similar to --only-section except it does not create a formatted file — it just dumps raw binary data, with no relocations applied. Can be specified more than once. ✨
  • --update-section sectionname=filename — replaces the existing contents of section sectionname with the contents of filename. The section size gets adjusted to the file size. Section flags for sectionname stay unchanged. For ELF files the section-to-segment mapping also remains unchanged — something you can’t do with --remove-section followed by --add-section. Can be specified more than once. 💖
Rename + update combo note: you can use --rename-section and --update-section together on one command line to both update and rename a section. In that case, pass the original section name to --update-section, and pass the original and new section names to --rename-section. 🌸
  • --add-symbol name=[section:]value[,flags] — adds a new symbol called name while copying. Can be specified multiple times. If section is given, the symbol is associated with and relative to that section; otherwise it’s an ABS symbol. Specifying an undefined section is a fatal error. There’s no check on the value — it’s taken as specified. Symbol flags can be specified, and not all flags are meaningful for all object file formats. By default the symbol is global. The special flag 'before=othersym' inserts the new symbol in front of the specified othersym; otherwise the symbol(s) are added at the end of the symbol table in the order they appear. 🔥
  • --rename-section oldname=newname[,flags] — renames section oldname to newname, optionally changing the section’s flags to flags in the process. Big advantage over using a linker script for the rename: the output stays an object file and does not become a linked executable. Accepts the same set of flags as --set-section-flags. 👑

This one is especially helpful when the input format is binary, because binary input always creates a section called .data. So if you wanted .rodata containing binary data instead, you could use this exact command line to make it happen:

objcopy -I binary -O <output_format> -B <architecture> \
 --rename-section .data=.rodata,alloc,load,readonly,data,contents \
 <input_binary_file> <output_object_file>
  • --long-section-names {enable,disable,keep} — controls how long section names are handled when processing "COFF" and "PE-COFF" object formats. The default, keep, preserves long section names if any are present in the input file. enable and disable forcibly enable or disable long section names in the output object; when disable is in effect, any long section names in the input object get truncated. enable only emits long section names if any are present in the inputs — mostly the same as keep, but it’s left undefined whether enable might force creation of an empty string table in the output file. 🦋
  • --change-leading-char — some object file formats use special characters at the start of symbols; the most common is underscore, which compilers often add before every symbol. This tells objcopy to change the leading character of every symbol when converting between object file formats. If both formats use the same leading character, this has no effect. Otherwise it adds a character, removes a character, or changes a character, as appropriate. 💫
  • --remove-leading-char — if the first character of a global symbol is the special symbol leading character used by the object file format, remove that character. The most common symbol leading character is underscore. This removes a leading underscore from all global symbols. Useful if you want to link together objects of different file formats with different conventions for symbol names. Different from --change-leading-char because it always changes the symbol name when appropriate, regardless of the object file format of the output file. 🎀
  • --reverse-bytes=num — reverses the bytes in a section with output contents. A section length must be evenly divisible by num for the swap to be able to take place. Reversing happens before the interleaving is performed. ⭐

This is typically used for generating ROM images for problematic target systems. Example: on some target boards, the 32-bit words fetched from 8-bit ROMs are re-assembled in little-endian byte order regardless of the CPU byte order. Depending on the programming model, the endianness of the ROM may need to be modified. Consider a simple file with a section containing these eight bytes: 12345678. 🍓

  • With --reverse-bytes=2 for the above example, the bytes in the output file would be ordered 21436587.
  • With --reverse-bytes=4 for the above example, the bytes in the output file would be ordered 43218765.
  • Using --reverse-bytes=2 for the above example, followed by --reverse-bytes=4 on the output file, the bytes in the second output file would be ordered 34127856.
  • --srec-len=ival — only meaningful for srec output. Sets the maximum length of the Srecords being produced to ival. This length covers both address, data and crc fields. ✨
  • --srec-forceS3 — only meaningful for srec output. Avoids generation of S1/S2 records, creating S3-only record format. 🌈
  • --redefine-sym old=new — changes the name of symbol old to new. Useful when you’re trying to link two things together, have no source, and there are name collisions. 🫶
  • --redefine-syms=filename — applies --redefine-sym to each symbol pair "old new" listed in filename. filename is a flat file with one symbol pair per line. Line comments may be introduced by the hash character. May be given more than once. 💜
  • --weaken — changes all global symbols in the file to be weak. Useful when building an object that will be linked against other objects using the -R option to the linker. Only effective when using an object file format that supports weak symbols. 💅
  • --keep-symbols=filename — applies --keep-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. 🌸
  • --strip-symbols=filename — applies --strip-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. 😭
  • --strip-unneeded-symbols=filename — applies --strip-unneeded-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. 💀
  • --keep-global-symbols=filename — applies --keep-global-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. 🦋
  • --localize-symbols=filename — applies --localize-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. 💖
  • --globalize-symbols=filename — applies --globalize-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. Note: this option cannot be used in conjunction with the -G or --keep-global-symbol options. 🚨
  • --weaken-symbols=filename — applies --weaken-symbol to each symbol listed in filename. filename is a flat file with one symbol name per line. Line comments may be introduced by the hash character. May be given more than once. 🎀
  • --alt-machine-code=index — if the output architecture has alternate machine codes, use the indexth code instead of the default one. Useful when a machine gets assigned an official code and the tool-chain adopts the new code, but other applications still depend on the original code being used. For ELF-based architectures, if the index alternative does not exist, the value is treated as an absolute number to be stored in the e_machine field of the ELF header. 🔥
  • --writable-text — marks the output text as writable. Not meaningful for all object file formats. ⭐
  • --readonly-text — makes the output text write protected. Not meaningful for all object file formats. 👑
  • --pure — flags your output file as demand paged ✨. Warning though bestie: this one isn't meaningful for all object file formats, so don't come for me if it does nothing on yours 💅
  • --impure — marks the output file as impure 🫶. Same deal, same disclaimer: not meaningful for every object file format out there.
  • --prefix-symbols=*string* — every single symbol in the output file gets string slapped on the front of it 💖 like a little name tag. All of them. No cap.
  • --prefix-sections=*string* — same energy but for sections: all section names in the output file start with string 🎀
  • --prefix-alloc-sections=*string* — extra specific icon behaviour: only the names of all the allocated sections in the output file get the string prefix 🌸
  • --add-gnu-debuglink=*path-to-file* — builds a .gnu_debuglink section that holds a reference to path-to-file, then adds it to the output file. Obsessed with this one for real. 💅

Heads up though: the file at path-to-file must exist. And part of the whole process of adding that .gnu_debuglink section involves embedding a checksum of the contents of the debug info file into the section 😭 so it's not just a string, it's a whole vibe.

So like — if your debug info file is built in one location but it's gonna get installed later into a different location, do not use the path to the installed location 🙈 The --add-gnu-debuglink option will fail, because the installed file doesn't exist yet, duh. Instead, put the debug info file in the current directory and use the --add-gnu-debuglink option without any directory components, like this:

objcopy --add-gnu-debuglink=foo.debug

At debug time, the debugger will attempt to look for the separate debug info file in a set of known locations. The exact set varies depending on the distribution being used, but it typically includes:

  • The same directory as the executable. 📁
  • A sub-directory of the directory containing the executable called .debug.
  • A global debug directory such as /usr/lib/debug.

As long as the debug info file has been installed into one of these locations before the debugger is run, everything should work correctly ✨ periodt.

  • --keep-section-symbols — when you're stripping a file, maybe with --strip-debug or --strip-unneeded, this one retains any symbols specifying section names, which would otherwise get stripped 😤 protective queen behaviour.
  • --keep-file-symbols — same but different: when stripping a file, perhaps with --strip-debug or --strip-unneeded, retain any symbols specifying source file names, which would otherwise get stripped 🥺 we keep the file-name symbols safe.
  • --only-keep-debug — strips a file, removing contents of any sections that wouldn't be stripped by --strip-debug, and leaving the debugging sections intact 💖 In ELF files, this preserves all note sections in the output.

Note — the section headers of the stripped sections are preserved, including their sizes, but the contents of the section are discarded. The headers stay so other tools can match up the debuginfo file with the real executable, even if that executable has been relocated to a different address space 🌀 iconic, honestly.

The intention is that this option gets used in conjunction with --add-gnu-debuglink to create a two part executable. One: a stripped binary that takes up less space in RAM and in a distribution. Two: a debugging information file which is only needed if debugging abilities are required. The suggested procedure to create these files is as follows:

  1. Link the executable as normal. Assuming that it is called "foo" then...
  2. Run objcopy --only-keep-debug foo foo.dbg to create a file containing the debugging info.
  3. Run objcopy --strip-debug foo to create a stripped executable.
  4. Run objcopy --add-gnu-debuglink=foo.dbg foo to add a link to the debugging info into the stripped executable.

Note — the choice of .dbg as an extension for the debug info file is arbitrary 🤷‍♀️ Also the --only-keep-debug step is optional. You could instead do this:

  1. Link the executable as normal.
  2. Copy "foo" to "foo.full".
  3. Run objcopy --strip-debug foo.
  4. Run objcopy --add-gnu-debuglink=foo.full foo.

i.e., the file pointed to by the --add-gnu-debuglink can be the full executable. It does not have to be a file created by the --only-keep-debug switch 💫 flexible!

Note — this switch is only intended for use on fully linked files. It does not make sense to use it on object files where the debugging information may be incomplete 😬 Besides, the gnu_debuglink feature currently only supports the presence of one filename containing debugging information, not multiple filenames on a one-per-object-file basis. So like... one file, one link. That's the rule.
  • --strip-dwo — removes the contents of all DWARF .dwo sections, leaving the remaining debugging sections and all symbols intact 🧚 This one's intended for use by the compiler as part of the -gsplit-dwarf option, which splits debug information between the .o file and a separate .dwo file. The compiler generates all debug information in the same file, then uses the --extract-dwo option to copy the .dwo sections to the .dwo file, then the --strip-dwo option to remove those sections from the original .o file. Cleanup crew energy 💅
  • --extract-dwo — extracts the contents of all DWARF .dwo sections 🌈 See the --strip-dwo option for more info, they're a matching set bestie.
  • --file-alignment num — specifies the file alignment. Sections in the file will always begin at file offsets which are multiples of this number. Defaults to 512 ✨ [This option is specific to PE targets.] 🎯
  • --heap reserve
  • --heap reserve,commit — specifies the number of bytes of memory to reserve (and optionally commit) to be used as heap for this program 🍓 [This option is specific to PE targets.] 🎯
  • --image-base value — uses value as the base address of your program or dll 👑 This is the lowest memory location that will be used when your program or dll is loaded. To reduce the need to relocate and improve performance of your dlls, each should have a unique base address and not overlap any other dlls 😤 no sharing. The default is 0x400000 for executables, and 0x10000000 for dlls. [This option is specific to PE targets.]
  • --section-alignment num — [This option is specific to PE targets.] 🎯

Sets the section alignment field in the PE header — if one is present in the binary. Sections in memory will always begin at addresses which are a multiple of this number. Defaults to 0x1000 🌸

Note — if a section's LMA or VMA addresses are no longer aligned, and those addresses have not been set via the --set-section-lma or --set-section-vma options, and the file has been fully relocated, then a warning message will be issued 😭 It will then be up to the user to decide if the LMA and VMA need updating. That's you, bestie. You decide. 🫵
  • --stack reserve
  • --stack reserve,commit — specifies the number of bytes of memory to reserve (and optionally commit) to be used as stack for this program 💜 [This option is specific to PE targets.] 🎯
  • --subsystem which
  • --subsystem which:major
  • --subsystem which:major.minor — specifies the subsystem under which your program will execute 🔥 The legal values for which are native, windows, console, posix, efi-app, efi-bsd, efi-rtd, sal-rtd, and xbox. You may optionally set the subsystem version also. Numeric values are also accepted for which 👑 [This option is specific to PE targets.] 🎯
  • --extract-symbol — keeps the file's section flags and symbols but removes all section data 🦋 Specifically, this option:
    • Removes the contents of all sections. 💀
    • Sets the size of every section to zero.
    • Sets the file's start address to zero.

This option is used to build a .sym file for a VxWorks kernel 🌟 It can also be a useful way of reducing the size of a --just-symbols linker input file. Efficiency queen.

  • --compress-debug-sections — compresses DWARF debug sections using zlib with SHF_COMPRESSED from the ELF ABI ✨ Note — if compression would actually make a section larger, then it is not compressed 🙅‍♀️ we don't do that here.
  • --compress-debug-sections=none
  • --compress-debug-sections=zlib
  • --compress-debug-sections=zlib-gnu
  • --compress-debug-sections=zlib-gabi
  • --compress-debug-sections=zstd — for ELF files, these options control how DWARF debug sections are compressed 💖
    • --compress-debug-sections=none is equivalent to --decompress-debug-sections.
    • --compress-debug-sections=zlib and --compress-debug-sections=zlib-gabi are equivalent to --compress-debug-sections.
    • --compress-debug-sections=zlib-gnu compresses DWARF debug sections using the obsoleted zlib-gnu format 😬 and the debug sections get renamed to begin with .zdebug.
    • --compress-debug-sections=zstd compresses DWARF debug sections using zstd 🔥
Note — if compression would actually make a section larger, then it is not compressed nor renamed 🌸
  • --decompress-debug-sections — decompresses DWARF debug sections 🦋 For a .zdebug section, the original name is restored 👑 we put it back, bestie.
  • --elf-stt-common=yes
  • --elf-stt-common=no — for ELF files, these options control whether common symbols should be converted to the STT_COMMON or STT_OBJECT type 🎀
    • --elf-stt-common=yes converts common symbol type to STT_COMMON. 💖
    • --elf-stt-common=no converts common symbol type to STT_OBJECT. ✨
  • --merge-notes
  • --no-merge-notes — for ELF files, attempt (or do not attempt) to reduce the size of any SHT_NOTE type sections by removing duplicate notes 🧹 dedupe slay.
  • -V, --version — shows the version number of objcopy 💅
  • --verilog-data-width=*bytes* — for Verilog output, this option controls the number of bytes converted for each output data element 🌈 The input target controls the endianness of the conversion.
  • -v, --verbose — verbose output: list all object files modified 🗒️ In the case of archives, objcopy -V lists all members of the archive 👀 (yes, that's a -V in there, copy it exactly, don't @ me).
  • --help — shows a summary of the options to objcopy 🫶
  • --info — displays a list showing all architectures and object formats available 🌟 the full menu, iykyk.
  • @file — reads command-line options from file 📄 The options read are inserted in place of the original @file option. If file does not exist, or cannot be read, then the option will be treated literally, and not removed — so it just stays there awkwardly 💀

Options in file are separated by whitespace. A whitespace character may be included in an option by surrounding the entire option in either single or double quotes 🎀 Any character (including a backslash) may be included by prefixing the character to be included with a backslash. The file may itself contain additional @file options; any such options will be processed recursively 🌀 it's files all the way down, bestie.

✨ SEE ALSO ✨

okay so you're done here but the ✨lore✨ continues, bestie:

  • ld(1) — the linker, aka the one who actually puts everything together 💅
  • objdump(1) — the nosy bestie who reads object files back to you, iconic behavior ngl 🔍
  • and the Info entries for binutils — the deep lore, the director's cut, the whole extended universe 📚✨

Okay so legal time, but make it cute 🫶 — here's the deal, word for word:

Copyright (c) 1991-2026 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation — with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. 💖

A copy of the license is included in the section entitled "GNU Free Documentation License" — so like, it's literally right there in the doc if you wanna read it, no cap 📖✨

and that's the whole page, bestie!! you made it to the end, so proud of you 😭💜 this lil masterpiece is from binutils-2.47 and it's dated 2026-08-26 — go forth and objcopy your heart out, the object files could never 💅🎀🦋

📦 where this page comes from