OBJCOPY(1)

👑 OBJCOPY(1) 👑

okay bestie, welcome to the GNU Development Tools manual page for objcopy — the copy-and-translate object files icon. We are gonna get you fluent in this, no cap. 💅

🌸 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 🌸

okay so objcopy is the GNU utility that copies the contents of an object file to another object file — it’s giving copy/paste but make it object-file aware. ✨ It uses the GNU BFD Library to read and write object files, and it can write the destination object file in a format different from the source object file. The exact behavior of objcopy is controlled by command-line options.

Big important vibe check: objcopy should be able to copy a fully linked file between any two formats. However, copying a relocatable object file between any two formats may not work as expected. Not me warning you in advance, but yes. 😭

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

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. Memory dump era, honestly.

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, bestie: 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 do not specify outfile, objcopy creates a temporary file and destructively renames the result with the name of infile.
• -I bfdname, --input-target=bfdname — consider the source file’s object format to be bfdname, rather than attempting to deduce it.
• -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 translation, 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. 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.
• -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. 💖

• -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. Undefined behaviour, bestie — do not play with that.

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. 🦋
• -S, --strip-all — do not copy relocation and symbol information from the source file. Also deletes debug sections.
• -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.
• -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. Protective energy for your fave symbol.
• -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 keeps only symbol symbolname global, bestie 💅. Every other symbol gets made local to the file so it’s not visible externally. You can pass this more than once. Note: this option cannot be used in conjunction with the --globalize-symbol or --globalize-symbols options.
• --localize-hidden — in an ELF object, this marks all symbols that have hidden or internal visibility as local. It applies on top of symbol-specific localization options such as -L. Lowkey iconic for tidying visibility ✨.
• -L symbolname, --localize-symbol=symbolname — converts a global or weak symbol called symbolname into a local symbol, so it’s not visible externally. This option may be given more than once. Note: unique symbols are not converted.
• -W symbolname, --weaken-symbol=symbolname — makes symbol symbolname weak. This option may be given more than once. Weakening, but make it fashion 🎀.
• --binary-symbol-prefix=string — when used 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, and <string>_size. By default, the binary input handler derives the prefix symbol name from a mangled version of the input file name and _binary prefix. This option lets you specify it explicitly. Ngl, very main character energy 👑.
• --globalize-symbol=symbolname — gives symbol symbolname global scoping so that it’s visible outside of the file in which it is defined. This option may be given more than once. Note: this option cannot be used in conjunction with the -G or --keep-global-symbol options.
• -w, --wildcard — permits regular expressions in symbolnames used in other command line options. The question mark (?), asterisk (*), backslash (\) and square brackets ([]) operators can be used anywhere in the symbol name. If the first character of the symbol name is the exclamation point (!) then the sense of the switch is 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". The way that works is lowkey satisfying fr fr 🫶.

• -x, --discard-all — do not copy non-global symbols from the source file. Bye-bye, local clutter 💀.
• -X, --discard-locals — do not copy compiler-generated local symbols. These usually start with L or .. Periodt, compiler, we see you 🙈.
• -b byte, --byte=byte — if interleaving has been enabled via the --interleave option, then 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. Very precise, very slay 🌸.
• -i [breadth], --interleave[=breadth] — only copy a range out of every breadth bytes. Header data is not affected. Select which byte in the range begins the copy with the --byte option. Select the width of the range with the --interleave-width option.

This option is useful for creating files to program ROM. It is typically used with an "srec" output target. Note that objcopy will complain if you do not specify the --byte option as well. 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. It’s giving “ROM builder bestie” 🔥.

• --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.

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. Literally a little byte choreography 💃.

• -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. Time-travel but make it file metadata ⭐.
• -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. Consistent archives are highkey the vibe 🌈.

• -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. So if you want the real-real metadata, this is your girl 💅.

• --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. Worth it when it works, though 🦋.
• --gap-fill val — fill gaps between sections with val. This operation applies to the load address (LMA) of the sections. It is done by increasing the size of the section with the lower address, and filling in the extra space created with val. Gap-filling: not glamorous, but necessary 🎀.
• --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). Padding queen 👑.
• --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. Respect the limits, bestie 🫶.
• --change-start incr, --adjust-start incr — change the start address (also known as the entry address) by adding incr. Not all object file formats support setting the start address. Same caveat, different flag ✨.
• --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. Danger zone: this is not a relocation, it’s just moving the label on the door 😭.
• --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 does not match any sections in the input file, a warning will be issued, unless --no-change-warnings is used. Matching patterns: very demure, very mindful 🧚.
• --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. LMA: load-time main character 💜.
• --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. Do not just vibe-check this in production, bestie. 💀

• --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. Warning: on brand, on purpose 🌸.
• --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. Sometimes you just don’t want the group chat to hear about it 🙈.
• --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. 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. Flags on flags on flags 💅✨.
• --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.... Power-of-two or it doesn’t count, no cap 🎀.

💖 Quick heads up before we go any further: setting a section's alignment does not magically align its LMA or VMA addresses too. If those need changing as well, you gotta reach for --change-section-lma and/or --change-section-vma. And also — tiny warning — messing with VMAs can cause problems in fully linked binaries, because there may be code in there that literally expects the section contents to live at their old address. Like, it's committed to that address, bestie. 🫠

• --add-section sectionname=filename — Adds a brand-new section called sectionname while it's copying the file. The new section's contents come straight from filename, and the section size = the file size. Only works on file formats that support sections with arbitrary names (iykyk which ones). 📎 Heads up: you might need to use --set-section-flags afterwards to set the attributes of the freshly created section.
• --dump-section sectionname=filename — Spills the contents of the section called sectionname into filename, overwriting whatever was chilling there before. This is the inverse of --add-section. It's kinda similar to --only-section, except it does not create a formatted file — it just dumps the raw binary data, with no relocations applied whatsoever. 🗑️ Can be specified more than once.
• --update-section sectionname=filename — Swaps out the existing contents of section sectionname for the contents of filename. The section size gets adjusted to the file's size, and the section flags for sectionname stay exactly the same. For ELF format files the section-to-segment mapping also remains unchanged — which is something you straight up can't do with --remove-section followed by --add-section. 🏆 Can be specified more than once.

🧚 Little note: you can use --rename-section and --update-section together on one command line to both update and rename a section. Just pass the original section name to --update-section, and both the original and new section names to --rename-section. Slay.

• --add-symbol name=[section:]value[,flags] — Adds a new symbol called name while copying the file. Can be specified multiple times. If you give the section, the symbol gets associated with and is relative to that section; otherwise it's an ABS symbol. Specifying an undefined section = fatal error 💀. There's no check on the value — it'll be taken exactly as specified, no questions asked. Symbol flags can be specified, but 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) get added at 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 while it's at it. The glow-up here vs. using a linker script: the output stays an object file and does not become a linked executable. 👑 This option accepts the same set of flags as --set-section-flags.

It's especially helpful when the input format is binary, because that always creates a section called .data. So if, say, you wanted to create a .rodata section containing binary data instead, you'd hit it with:

          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 processing "COFF" and "PE-COFF" object formats. The default behaviour, keep, 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 ✂️. 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 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. The most common one is underscore, which compilers often slap in front of every single symbol. This option tells objcopy to change the leading character of every symbol when converting between object file formats. If the formats use the same leading character, this option does absolutely nothing. 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, remove it. The most common symbol leading character is underscore, so this option will strip a leading underscore from all global symbols. Useful if you wanna link together objects of 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 the output file's object file format.
• --reverse-bytes=num — Reverses the bytes in a section with output contents. A section length has to be evenly divisible by the value you give, otherwise the swap can't happen. Reversing takes place before the interleaving is performed. 🔃

This option typically gets used for generating ROM images for problematic target systems. Like, 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. Depending on the programming model, the endianness of the ROM may need to be modified.

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

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

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

And by using --reverse-bytes=2 on the example above, followed by --reverse-bytes=4 on the output file, the bytes in that second output file would be ordered 34127856. math is mathing ✨

• --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 generation of S1/S2 records, creating an S3-only record format. 🎀
• --redefine-sym old=new — Changes the name of a symbol from old to new. Super useful when you're trying to link two things together, you have no source for them, and there are name collisions. 💥
• --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. Handy when building an object that'll be linked against other objects using the -R option to the linker. Only effective when using an object file format that actually supports weak symbols. 🫠
• --keep-symbols=filename — Applies --keep-symbol to each symbol listed in the file filename. filename is a flat file with one symbol name per line, and line comments can be introduced by the hash character. May be given more than once. 🌸
• --strip-symbols=filename — Applies --strip-symbol to each symbol listed in filename. Flat file, one symbol name per line, # starts a line comment, may be given more than once. 🧹
• --strip-unneeded-symbols=filename — Applies --strip-unneeded-symbol to each symbol listed in filename. Flat file, one symbol name per line, # for line comments, may be given more than once. 🗑️
• --keep-global-symbols=filename — Applies --keep-global-symbol to each symbol listed in filename. Flat file, one symbol name per line, # for line comments, may be given more than once. 👑
• --localize-symbols=filename — Applies --localize-symbol to each symbol listed in filename. Flat file, one symbol name per line, # for line comments, may be given more than once. 🏠
• --globalize-symbols=filename — Applies --globalize-symbol to each symbol listed in filename. Flat file, one symbol name per line, # for line comments, may be given more than once. 🌍 Note: this option cannot be used in conjunction with the -G or --keep-global-symbol options — pick a lane, bestie.
• --weaken-symbols=filename — Applies --weaken-symbol to each symbol listed in filename. Flat file, one symbol name per line, # for line comments, 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 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, 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. Also not meaningful for all object file formats. 🔒
• --pure — marks the output file as demand paged, bestie. This one isn’t meaningful for all object file formats, so don’t come for it if your format doesn’t care. 💅
• --impure — marks the output file as impure. Same vibe check as above: this option isn’t meaningful for all object file formats.
• --prefix-symbols=string — slaps string onto the front of every symbol in the output file. Prefix party, no cap.
• --prefix-sections=string — same energy, but for all section names in the output file: every one gets string prepended.
• --prefix-alloc-sections=string — and this one prefixes all the names of all allocated sections in the output file with string. Allocated girlies get their own flag, iconic.
• --add-gnu-debuglink=path-to-file — creates a .gnu_debuglink section that contains a reference to path-to-file and adds it to the output file. Note: the file at path-to-file must exist, fr fr. Part of the process of adding the .gnu_debuglink section involves embedding a checksum of the contents of the debug info file into the section.

If the debug info file is built in one location but it is going to be installed at a later time into a different location, then do not use the path to the installed location. The --add-gnu-debuglink option will fail because the installed file does not exist yet. 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 of these locations varies depending upon 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. 🫶

• --keep-section-symbols — when stripping a file, perhaps with --strip-debug or --strip-unneeded, this retains any symbols specifying section names, which would otherwise get stripped. Keeping the section-name girlies employed. ✨
• --keep-file-symbols — when stripping a file, perhaps with --strip-debug or --strip-unneeded, this retains any symbols specifying source file names, which would otherwise get stripped. Source-file symbols stay booked and busy.
• --only-keep-debug — strips a file, removing contents of any sections that would not 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 section headers are preserved so that other tools can match up the debuginfo file with the real executable, even if that executable has been relocated to a different address space.

The intention is that this option will be used in conjunction with --add-gnu-debuglink to create a two part executable. One is a stripped binary which will occupy less space in RAM and in a distribution, and the second is 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.

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. 😭

• --strip-dwo — removes the contents of all DWARF .dwo sections, leaving the remaining debugging sections and all symbols intact. This option is 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. Compiler girlies ate with this one. 🔥
• --extract-dwo — extracts the contents of all DWARF .dwo sections. See the --strip-dwo option for more information. It’s giving “copy the dwo bits out, bestie.”
• --file-alignment num — specifies the file alignment. Sections in the file will always begin at file offsets which are multiples of this number. This 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. 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. ⚠️

• --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. Little stripped-down icon. 💜

• --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. No glow-up if it makes things bigger, rude.
• --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. The debug sections are 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. Name restored, skin cleared, slay. ✨
• --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". Symbol type makeover, no cap.
• --merge-notes, --no-merge-notes — for ELF files, attempts (or does not attempt) to reduce the size of any SHT_NOTE type sections by removing duplicate notes. Duplicate notes? Not on our watch. 💅
• -V, --version — shows the version number of objcopy. Quick vibe check on which objcopy you’re running.
• --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. Verilog besties, this one’s for you. 🦋
• -v, --verbose — verbose output: lists all object files modified. In the case of archives, objcopy -V lists all members of the archive. Yes, that’s -V right there in the original — copying it exactly, bestie. 👑
• --help — shows a summary of the options to objcopy. Your little menu of possibilities.
• --info — displays a list showing all architectures and object formats available. It’s giving “what can this thing even do?” energy. 🌸
• @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. 🙈

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. Recursive file options? She’s nested, she’s iconic, she’s processing. 💖

✨ SEE ALSO ✨

okay so when you're done vibing with objcopy and you wanna keep the party going, go check out these besties:

• ld(1) — the linker, the one who actually puts all your pieces together 💅
• objdump(1) — the nosy queen who'll show you what's inside any object file, icon behavior fr
• and the Info entries for binutils — like, the full lore, not just the highlights ✨

---

🎀 COPYRIGHT 🎀

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

okay so legally speaking, here's the tea 🍵 — you're fully allowed to copy, distribute, and/or modify this document, no cap. The conditions are the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation. Slay.

The fine print, and yes it matters:

• no Invariant Sections 🙅‍♀️
• no Front-Cover Texts 🙈
• no Back-Cover Texts 🙊

And if you want the actual license text, a copy of it is included in the section entitled "GNU Free Documentation License" — it's giving very "the receipts are right there, bestie" 💜

---

lowkey the most responsible thing in this whole manpage and it's still cute. main character energy. periodt. 👑

---

and that's a wrap on the whole thing, bestie 🫶 you made it to the end — this page is from binutils-2.47, dated 2026-07-30, and honestly? iconic. go forth and copy your objects with confidence 💖✨🌸