OBJCOPY(1)

👑 OBJCOPY(1) — GNU Development Tools 👑

okay bestie, sit down, hydrate, because we are about to talk about objcopy from the GNU Development Tools and she is that girl 💅

---

🌸 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 an object file to another one. Slay. 🫶 objcopy uses the GNU BFD Library to read and write the object files, and bestie, it can write the destination object file in a format different from that of the source object file. The exact behavior of objcopy is controlled by command-line options.

⚠️ okay real talk: 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. Not me warning you, but like, I'm warning you. 😭

objcopy creates temporary files to do its translations and deletes them afterward. It uses BFD to do all its translation work, so it has access to all the formats described in BFD and is thus able to recognize most formats without being told explicitly. iconic behavior honestly.

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

objcopy can 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. 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.) no cap, that's just how it is.

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✨ OPTIONS ✨

• infile
• outfile — The input and output files, respectively. If you do not specify outfile, objcopy creates a temporary file and destructively renames the result with the name of infile. 💀 lowkey scary but okay.

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🌈 Input / output format vibes 🌈

• -I bfdname, --input-target=bfdname — Consider the source file's object format to be bfdname, rather than attempting to deduce it. Like, just tell her, she doesn't have to guess. 💅
• -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.
• -B bfdarch, --binary-architecture=bfdarch — Useful when transforming a 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. These 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. 🎀 so cute, so useful.

---

🌸 Section selection (the picky eater era) 🌸

• -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 sectinos matching .text.* but not the section .text.foo. 🦋

• -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. 🚨 like don't do that bestie.

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. 🫶
• --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. 👑

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💅 Stripping (the glow-down) 💅

• -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. 🧚

---

🎀 Per-symbol control 🎀

• -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. protecting her faves fr fr 💖
• -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 — okay so this one is like the VIP list 💅. Keep only symbolname as global, and demote literally every other symbol to local so nobody outside the file can see them. You can stack this option more than once (multiple VIPs, we love that). But bestie, careful: this cannot be used together with the --globalize-symbol or --globalize-symbols options. They fight. Don't make them fight.
• --localize-hidden — for ELF objects, this marks every symbol with hidden or internal visibility as local. It layers on top of your symbol-specific localization options like -L, so it's not replacing them, it's adding to the vibe ✨.
• -L symbolname, --localize-symbol=symbolname — take a global or weak symbol called symbolname and turn it into a local symbol so it's not visible externally. Can be given more than once. Note: unique symbols do not get converted. Sorry to them.
• -W symbolname, --weaken-symbol=symbolname — make symbolname weak 💀. That's it, that's the whole thing. Can be given more than once.
• --binary-symbol-prefix=string — when you're rolling 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 just lets you say it out loud instead 🙈.

• --globalize-symbol=symbolname — give symbolname global scoping so it's visible outside the file where it's defined. Can be given more than once. Note: this cannot be used with the -G or --keep-global-symbol options. Pick a lane, bestie.
• -w, --wildcard — permits regular expressions in the symbolnames used in your other command line options 🎀. The ?, *, \ and [] operators can go anywhere in the symbol name. And here's the spicy bit: if the first character of the symbol name is !, the sense of the switch gets reversed for that symbol. Like:

-w -W !foo -W fo*

which would make objcopy weaken all symbols that start with "fo" except for the symbol "foo". Iconic behaviour honestly.

• -x, --discard-all — do not copy non-global symbols from the source file. Bye 👋.
• -X, --discard-locals — do not copy compiler-generated local symbols. (These usually start with L or ..) Not us throwing shade, that's just literally what they're named.
• -b byte, --byte=byte — if interleaving is enabled via --interleave, this starts the range of bytes to keep at the byteth byte. byte can be from 0 to breadth-1, where breadth is whatever you gave --interleave.
• -i [breadth], --interleave[=breadth] — only copy a range out of every breadth bytes. (Header data is not affected, don't worry.) Use --byte to pick which byte in the range starts the copy, and --interleave-width to pick the width of the range 🌸.

This one is lowkey made for creating files to program ROM, and it's typically used with an "srec" output target. Note: objcopy will complain if you don't also specify the --byte option. It needs both of you.

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.

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

Default value is 1. And the rule: the value of width plus the byte value set by --byte must not exceed the interleave breadth set by --interleave. Math is math 💅.

This can make 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. Chef's kiss.

• -p, --preserve-dates — set the access and modification dates of the output file to match the input file's 🫶.

It 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 that variable gets used as the date stored in the header, interpreted as the number of seconds since the Unix epoch.

• -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.

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. It's the inverse of -D 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.

• --debugging — convert debugging information, if possible. Not the default, because only certain debugging formats are supported and the conversion process can be time consuming 😭. So it's a whole thing, not a casual tap.
• --gap-fill val — fill gaps between sections with val. This applies to the load address (LMA) of the sections. It works by increasing the size of the section with the lower address, and filling the extra space created with val.
• --pad-to address — pad the output file up to the load address address. Done by increasing the size of the last section, and the extra space is filled in with the value specified by --gap-fill (default zero).
• --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, so no promises ✨.
• --change-start incr, --adjust-start incr — change the start address (also known as the entry address) by adding incr. Again, 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, plus the start address, by adding incr. Some object file formats do not permit section addresses to be changed arbitrarily. And listen: this does not relocate the sections. If the program expects sections to be loaded at a certain address and you use this to move them somewhere else, the program may fail. Like, may genuinely not work. So know what you're doing 💀.
• --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 👆. If sectionpattern doesn't match any sections in the input file, a warning gets 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 ones where the 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 doesn't match anything in the input file, you get a warning 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 where the section will be located once the program has started executing. Normally it's the same as the LMA address (where the section is loaded into memory), but on some systems — especially ROM-held programs — the two can differ. 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 doesn't match anything in the input file, a warning is 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. Respect the old address, it has feelings 🥺.

• --change-warnings, --adjust-warnings — if --change-section-address or --change-section-lma or --change-section-vma is used, and the section pattern doesn't match any sections, issue a warning. This is the default. It's just looking out for you 🫶.
• --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 doesn't match any sections. Silence. Blessed silence 🤫.
• --set-section-flags sectionpattern=flags — set the flags for any sections matching sectionpattern. The flags argument is a comma separated string of flag names, and 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 that doesn't have contents, but it is not meaningful to clear the contents flag of a section that 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. And the ELF x86-64 specific flag large corresponds to SHF_X86_64_LARGE.
• --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.... No chaotic in-between numbers, okay? Powers of two only 💖.

⚠️ heads up bestie — setting a section's alignment will NOT automatically align its LMA or VMA addresses. Like, those are separate things, okay? If you actually need those moved you gotta reach for --change-section-lma and/or --change-section-vma yourself. Also, and this is the tea: messing with VMAs can cause problems in fully linked binaries, because there might be code in there that literally expects the section contents to still be chillin' at their old address. 💀

---

• --add-section sectionname=filename — adds a whole new section called sectionname while it's copying the file. 🎀 The contents of that shiny new section come straight from the file filename, and its size is just the size of that file. This only works on file formats that can actually handle sections with arbitrary names, so don't @ it if your format can't. 📝 Note — you might have to bring --set-section-flags along to give your brand new section its attributes.
• --dump-section sectionname=filename — takes the contents of the section named sectionname and drops them into the file filename, overwriting whatever was already in there. It's the inverse of --add-section, the mirror twin, the evil twin but make it useful. ✨ It's similar to --only-section except it doesn't make a formatted file — it just dumps the raw binary data, no relocations applied, no frills, no makeup. 💅 You can specify this option more than once.
• --update-section sectionname=filename — swaps out the existing contents of section sectionname for the contents of file filename. The section's size gets adjusted to match the file, and the section flags for sectionname stay exactly as they were. 🫶 For ELF format files, the section-to-segment mapping stays unchanged too — which is a whole thing you can't pull off with --remove-section followed by --add-section. You can specify this option more than once.

Note — you can actually use --rename-section and --update-section together on one command line to both update and rename a section, iconic combo behavior. 👑 In that case, pass the original section name to --update-section, and pass both the original and the new section names to --rename-section.

• --add-symbol name=[section:]value[,flags] — adds a new symbol named name while copying. Can be specified multiple times, no cap fr. 🌈 If you give a section, the symbol gets associated with and is relative to that section; otherwise it's an ABS symbol. Specifying an undefined section is a fatal error — so, like, don't. There's no check on the value either, it just takes whatever you said. You can also specify symbol flags, though not all flags are meaningful for all object file formats (rude, but true). 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) get tacked onto the end of the symbol table in the order they appear. 🍓
• --rename-section oldname=newname[,flags] — renames a section from oldname to newname, optionally changing the section's flags to flags along the way. ✨ The glow-up here versus using a linker script for the rename is that the output stays an object file and does not become a linked executable. It accepts the exact same set of flags as --set-section-flags.

This one is especially helpful when your input format is binary, because binary input will always create a section called .data. So if you wanted, say, a section called .rodata holding binary data instead, you could use this 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 get handled when you're processing COFF and PE-COFF object formats. 🎀 Default behavior is keep, which preserves long section names if any are present in the input file. enable and disable forcibly turn the use of long section names on or off in the output object. When disable is in effect, any long section names in the input object get truncated. The enable option will only emit long section names if any are present in the inputs — mostly the same as keep, except it's left undefined whether enable might force the 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, and the most common one is the underscore, which compilers love to slap in front of every single symbol. 😭 This tells objcopy to change the leading character of every symbol when it converts between object file formats. If both formats use the same leading character, this does absolutely nothing, vibe check failed. Otherwise it'll add a character, remove a character, or change a character, as appropriate. 💅
• --remove-leading-char — if the first character of a global symbol is a special symbol leading character used by the object file format, it removes that character. The most common symbol leading character is underscore, so basically this strips a leading underscore off all global symbols. Super handy if you want to link together objects from different file formats that have different conventions for symbol names. 🫶 This is different from --change-leading-char because it always changes the symbol name when appropriate, regardless of what the output file's object format is. No cap.
• --reverse-bytes=num — reverses the bytes in a section with output contents. A section length must be evenly divisible by the value you give, otherwise the swap just cannot take place. 🙈 Reversing happens before the interleaving is performed.

This is typically used for generating ROM images for problematic target systems. For example, on some target boards the 32-bit words fetched from 8-bit ROMs get re-assembled in little-endian byte order regardless of the CPU byte order, and depending on the programming model the endianness of the ROM might need to be modified. It's giving hardware chaos. 💀

Consider a simple file with a section containing these eight bytes: 12345678.

Using --reverse-bytes=2 for the above example, the bytes in the output file would be ordered 21436587.

Using --reverse-bytes=4 for the above example, the bytes in the output file would be ordered 43218765.

By 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 the address, data and crc fields. ⭐
• --srec-forceS3 — only meaningful for srec output. Avoids generating S1/S2 records, creating an 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 and you have no source for either, and there are name collisions. Classic. 😭
• --redefine-syms=filename — applies --redefine-sym to each symbol pair "old new" listed in the file filename. filename is just a flat file with one symbol pair per line. Line comments can be introduced with the hash character. This option may be given more than once. 🌸
• --weaken — changes all global symbols in the file to be weak. Useful when you're building an object that'll be linked against other objects using the -R option to the linker. This option is only effective when using an object file format that supports weak symbols. 💜
• --keep-symbols=filename — applies --keep-symbol to each symbol listed in the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option may be given more than once. ✨
• --strip-symbols=filename — applies --strip-symbol to each symbol listed in the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option may be given more than once. ✨
• --strip-unneeded-symbols=filename — applies --strip-unneeded-symbol to each symbol listed in the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option may be given more than once. ✨
• --keep-global-symbols=filename — applies --keep-global-symbol to each symbol listed in the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option may be given more than once. ✨
• --localize-symbols=filename — applies --localize-symbol to each symbol listed in the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option may be given more than once. ✨
• --globalize-symbols=filename — applies --globalize-symbol to each symbol listed in the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option 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 the file filename. filename is just a flat file with one symbol name per line, and line comments can be introduced with the hash character. This option 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. Handy in case a machine gets assigned an official code and the toolchain adopts the new code, but other applications still depend on the original code being used. 👑 For ELF based architectures, if the index alternative doesn't exist then 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. This option isn't meaningful for all object file formats. 💅
• --readonly-text — makes the output text write protected. This option isn't meaningful for all object file formats. 🔒
• --pure — marks the output file as demand paged. 💅 Heads up tho, this one isn't meaningful for every object file format, so don't be shocked if it's giving nothing on your target.
• --impure — marks the output file as impure. Same vibe check as above: not meaningful for all object file formats.
• *--prefix-symbols=string* — takes every single symbol in the output file and slaps string on the front of it. glow up via prefix, bestie ✨
• *--prefix-sections=string* — same energy but for section names: every section name in the output file gets string glued to the start. 🎀
• *--prefix-alloc-sections=string* — only the allocated sections get the string prefix treatment. exclusive club, iykyk 💅
• *--add-gnu-debuglink=path-to-file* — okay this one is lowkey iconic. It creates a .gnu_debuglink section that holds a reference to path-to-file, and adds that section to the output file. 🦋

Real talk: the file at path-to-file must exist. Part of making that .gnu_debuglink section involves embedding a checksum of the contents of the debug info file right into the section. No file, no checksum, no section.

And here's the trap 🙈 if your debug info file is built in one location but is gonna be installed somewhere else later, do not use the path to the installed location. --add-gnu-debuglink will straight up fail because the installed file doesn't exist yet. Instead, drop the debug info file in the current directory and call --add-gnu-debuglink with no directory components at all, like this:

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

Then at debug time, the debugger goes hunting for that separate debug info file in a bunch of known locations. The exact set depends on your distribution, 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 those spots before the debugger runs, everything should work correctly. periodt 💖

• --keep-section-symbols — when you're stripping a file (say with --strip-debug or --strip-unneeded), this keeps any symbols that specify section names, which would otherwise get stripped away. 🫶
• --keep-file-symbols — same deal, but for the ones specifying source file names: when stripping (maybe via --strip-debug or --strip-unneeded), those symbols are retained instead of getting yeeted. 🥺
• --only-keep-debug — strips a file by removing the contents of any sections that --strip-debug would not strip, while 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 get discarded. Why keep the headers? 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. teamwork fr fr 🤝

The intention is that you use this with --add-gnu-debuglink to build a two part executable: one stripped binary that takes up less space in RAM and in a distribution, and a second debugging information file that's only needed if you actually want to debug. The suggested procedure goes like this:

1. Link the executable as normal. Assuming it's 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 --add-gnu-debuglink can be the full executable. It does not have to be a file created by the --only-keep-debug switch. 💅

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. soz 🫠

• --strip-dwo — removes the contents of all DWARF .dwo sections, leaving the remaining debugging sections and all symbols intact. This one is meant for the compiler to use as part of the -gsplit-dwarf option, which splits debug information between the .o file and a separate .dwo file. The compiler generates all the debug info in the same file, then uses --extract-dwo to copy the .dwo sections over to the .dwo file, then uses --strip-dwo to remove those sections from the original .o file. 🧚
• --extract-dwo — extracts the contents of all DWARF .dwo sections. See --strip-dwo above for the full tea. 🍓
• --file-alignment num — sets the file alignment. Sections in the file will always begin at file offsets that are multiples of this number. Defaults to 512. [This option is specific to PE targets.] 🎯
• --heap reserve, --heap reserve,commit — tells it how many 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 gets used when your program or dll is loaded. To reduce the need to relocate and improve performance of your dlls, each one should have a unique base address and not overlap any other dlls. 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 that 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 gets issued. After that it's up to you, the user, to decide if the LMA and VMA need updating. 👀

• --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 can optionally set the subsystem version too. 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 is used to build a .sym file for a VxWorks kernel. It can also be a genuinely useful way of reducing the size of a --just-symbols linker input file. 🔥

• --compress-debug-sections — compresses DWARF debug sections using zlib with SHF_COMPRESSED from the ELF ABI. Note — if the compression would actually make a section larger, then it just doesn't get compressed. no glow-down allowed 🚫
• --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 control how DWARF debug sections get compressed. Here's the breakdown:
  • --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. 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 and not renamed. 💀

• --decompress-debug-sections — decompresses DWARF debug sections. For a .zdebug section, the original name is restored. 🦋
• --elf-stt-common=yes, --elf-stt-common=no — for ELF files, these control whether common symbols get 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. pick your fighter 💅
• --merge-notes, --no-merge-notes — for ELF files, attempt (or don't attempt) to reduce the size of any SHT_NOTE type sections by removing duplicate notes. slay, dedupe 🎀
• -V, --version — shows the version number of objcopy. 🫶
• *--verilog-data-width=bytes* — for Verilog output, this controls the number of bytes converted for each output data element. The input target controls the endianness of the conversion. ⭐
• -v, --verbose — verbose output: lists all object files modified. In the case of archives, objcopy -V lists all members of the archive. 🔍
• --help — shows a summary of the options to objcopy. 😌
• --info — displays a list showing all architectures and object formats available. window shopping fr 🛍️
• *@file* — reads command-line options from file. The options read get inserted in place of the original @file option. If file doesn't exist, or can't be read, then the option is treated literally, and not removed. 🙈

Options in file are separated by whitespace. A whitespace character can be included in an option by surrounding the entire option in either single or double quotes. Any character (including a backslash) can be included by prefixing the character to be included with a backslash. The file may itself contain additional @file options; any such options get processed recursively. it's giving inception 😭

👀 SEE ALSO 👀

ok so if you're nosy (respectfully) and wanna go deeper, bestie, go bother these:

• ld(1) — the linker, the one who actually assembles the final vibe 💅
• objdump(1) — the other half of the duo, she reads what you just wrote, iconic
• and the Info entries for binutils — yes, Info entries, not man pages, she's fancy like that 🎀

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💖 COPYRIGHT 💖

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

ngl this next part is the legal slay, and you do have permission, so:

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, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

like, copy it, share it, remix it, go off 🫶 — just no invariant sections, no front-cover texts, no back-cover texts, periodt. and the full license text is chilling in the section called "GNU Free Documentation License" if you wanna read the whole thing (iykyk).

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and that's a wrap on the whole page, bestie 🎬✨ this one came from binutils-2.47, dated 2026-08-11, and yeah — OBJCOPY(1) ate and left no crumbs. go copy some objects, main character 👑💜