OBJCOPY(1)

okay bestie, welcome to the OBJCOPY(1) page from GNU Development Tools — this is the group chat where we learn how to copy and translate object files. 💅✨

🎀 NAME 🎀

objcopy — copy and translate object files. literally the whole vibe.

✨ 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]
        [-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]
        [-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]
        [--remove-relocations=sectionpattern]
        [-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]
        [--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]
        [--globalize-symbols=filename]
        [--weaken-symbols=filename]
        [--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]
        [--keep-file-symbols]
        [--only-keep-debug]
        [--strip-dwo]
        [--extract-dwo]
        [--extract-symbol]
        [--writable-text]
        [--readonly-text]
        [--pure]
        [--impure]
        [--file-alignment=num]
        [--heap=size]
        [--image-base=address]
        [--section-alignment=num]
        [--stack=size]
        [--subsystem=which:major.minor]
        [--compress-debug-sections]
        [--decompress-debug-sections]
        [--elf-stt-common=val]
        [--merge-notes]
        [--no-merge-notes]
        [-v|--verbose]
        [-V|--version]
        [--help] [--info]
        infile [outfile]

💅 DESCRIPTION 💅

The GNU objcopy utility copies the contents of an object file to another. It uses the GNU BFD Library to read and write the object files. 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.

Bestie, important note: 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. 😭

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. iconic, 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 the rule.

---

🔥 OPTIONS 🔥

one bullet per flag, bestie — no skips, no crumbs.

• 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.
• -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.

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.

• --remove-relocations=sectionpattern — remove 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. 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.

• -S, --strip-all — do not copy relocation and symbol information from the source file.
• -g, --strip-debug — do not copy debugging symbols or sections from the source file.
• --strip-unneeded — strip all symbols that are not needed for relocation processing.
• -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.
• -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 — keep only symbol symbolname global. Make all other symbols local to the file, so that they are not visible externally. This option may be given more than once.
• --localize-hidden — in an ELF object, mark all symbols that have hidden or internal visibility as local. This option applies on top of symbol-specific localization options such as -L.
• -L symbolname, --localize-symbol=symbolname — convert a global or weak symbol called symbolname into a local symbol, so that it is not visible externally. This option may be given more than once. Note — unique symbols are not converted.
• -W symbolname, --weaken-symbol=symbolname — make symbol symbolname weak. This option may be given more than once.
• --globalize-symbol=symbolname — Give symbol symbolname global scoping so it’s visible outside the file it’s defined in. You can drop this option more than once, bestie. 💅
• -w, --wildcard — Permit 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". iykyk 😌

• -x, --discard-all — Do not copy non-global symbols from the source file. Bye local besties 👋
• -X, --discard-locals — Do not copy compiler-generated local symbols. (These usually start with L or ..) fr fr, they’re giving compiler clutter 💀
• -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. tiny detail, big impact ✨
• -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. slay the bytes 🔥

• --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. iconic split 💅

• -p, --preserve-dates — Set the access and modification dates of the output file to be the same as those of the input file. keep the timestamps cute 🎀
• -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. no cap 🫶

• -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. periodt 💜

• --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. highkey a whole process 😭
• --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. 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). 🎀
• --set-start val — Set the start address of the new file to val. Not all object file formats support setting the start address. sad but true 💀
• --change-start incr, --adjust-start incr — Change the start 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. ⚠️ not me breaking the binary
• --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. 💅
• --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. ROM girlies understand 🔥
• --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. VMA vs LMA is giving main character energy 👑
• --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. 🌸
• --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. shhh 🤫
• --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, share, and debug. 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. flags are a vibe check 💅
• --add-section sectionname=filename — Add a new section named sectionname while copying the file. The contents of the new section are taken from the file filename. The size of the section will be the size of the file. This option only works on file formats which can support sections with arbitrary names. Note — it may be necessary to use the --set-section-flags option to set the attributes of the newly created section. new section just dropped ✨
• --dump-section sectionname=filename — Place the contents of section named sectionname into the file filename, overwriting any contents that may have been there previously. This option is the inverse of --add-section. This option is similar to the --only-section option except that it does not create a formatted file, it just dumps the contents as raw binary data, without applying any relocations. The option can be specified more than once. raw dump, no filter 😌
• --update-section sectionname=filename — Replace the existing contents of a section named sectionname with the contents of file filename. The size of the section will be adjusted to the size of the file. The section flags for sectionname will be unchanged. For ELF format files the section to segment mapping will also remain unchanged, something which is not possible using --remove-section followed by --add-section. The option can be specified more than once.

Note — it is possible to use --rename-section and --update-section to both update and rename a section from one command line. In this case, pass the original section name to --update-section, and the original and new section names to --rename-section. combo move, obsessed 🎀

• --add-symbol name=[section:]value[,flags] — Add a new symbol named name while copying the file. This option may be specified multiple times. If the section is given, the symbol will be associated with and relative to that section, otherwise it will be an ABS symbol. Specifying an undefined section will result in a fatal error. There is no check for the value, it will be taken as specified. Symbol flags can be specified and not all flags will be meaningful for all object file formats. By default, the symbol will be global. The special flag before=othersym will insert the new symbol in front of the specified othersym, otherwise the symbol(s) will be added at the end of the symbol table in the order they appear. symbol table glow-up 💖
• --rename-section oldname=newname[,flags] — bestie, this one renames a section from oldname to newname, and if you're feeling spicy you can also swap the section's flags to flags while you're in there 💅. The glow-up here vs. using a linker script to do the rename? Your output stays an object file and does not turn into a linked executable. Iconic.

This is lowkey a lifesaver when your input format is binary, because binary input always makes a section called .data. So say you wanted a section called .rodata holding your binary data instead — here's the exact command line for that:

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 ✨. The default is keep, which preserves long section names if there are any chillin' in the input file. enable and disable forcibly turn 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 😭. And enable 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. iykyk.
• --change-leading-char — okay so some object file formats put special characters at the start of symbols, and the most common one is 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 literally nothing. Otherwise it'll add a character, remove a character, or change a character, as appropriate. Slay.
• --remove-leading-char — if the first character of a global symbol is a special symbol-leading character used by the object file format, this yeets that character 🫶. The most common leading character is underscore, so this removes a leading underscore from all global symbols. Super useful if you want to link together objects from different file formats that have different conventions for symbol names. Heads up though: 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. Periodt.
• --reverse-bytes=num — reverses the bytes in a section that has output contents 🔥. The section length has to be evenly divisible by the value you give, otherwise the swap can't happen. Reversing happens before the interleaving is performed. Ngl 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 ROM's endianness may need to be modified.

Picture a simple file with a section containing these 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.
• Using --reverse-bytes=2 on the example above, then --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. That 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. S3 or bust.
• --redefine-sym old=new — changes the name of symbol old to new 🎀. Genuinely useful when you're trying to link two things together, you have no source for either of them, and the names are colliding. Name collision? Not on my watch.
• --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. Fr fr.
• --weaken — changes all global symbols in the file to be weak 💅. Handy when you're building an object that'll be linked against other objects using the -R option to the linker. Only effective when you're using an object file format that supports weak symbols. No support, no effect, sorry bestie.
• --keep-symbols=filename — applies --keep-symbol to each symbol listed in filename 🌸. filename is a flat file, one symbol name per line, and line comments may 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 filename 🧚. Same deal: flat file, one symbol name per line, line comments via the hash character #, and this option 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, line comments introduced by the hash character #. This option 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, line comments may be introduced by the hash character #. This option 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, line comments may be introduced by the hash character #. This option 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, line comments may be introduced by the hash character #. This option may be given more than once.
• --weaken-symbols=filename — applies --weaken-symbol to each symbol listed in filename 🍓. Flat file, one symbol name per line, line comments may be introduced by 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 index-th code instead of the default one 💀. Useful in case 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 doesn't exist then the value is treated as an absolute number to be stored in the e_machine field of the ELF header. Sneaky but valid.
• --writable-text — marks the output text as writable 🔥. Heads up: this option isn't meaningful for all object file formats.
• --readonly-text — makes the output text write protected 🎀. Also not meaningful for all object file formats, so don't come for me if your format shrugs at it.
• --pure — marks the output file as demand paged ✨. Again — not meaningful for all object file formats.
• --impure — marks the output file as impure 😈. Same caveat, bestie: not meaningful for all object file formats.
• --prefix-symbols=string — prefixes all symbols in the output file with string 💖.
• --prefix-sections=string — prefixes all section names in the output file with string 🦋.
• --prefix-alloc-sections=string — prefixes the names of all allocated sections in the output file with string 🌸.
• --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 🔗. Part of the process involves embedding a checksum of the contents of the debug info file into the section. Chef's kiss.

Note: the file at path-to-file must exist 🙈.

And listen — if the debug info file gets built in one location but it's going to be 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 😭. 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 you're using, 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. Slay 🫶.

• --keep-file-symbols — when stripping a file, maybe with --strip-debug or --strip-unneeded, retain any symbols that specify source file names, which would otherwise get stripped 💅. Protect the file symbols at all costs.
• --only-keep-debug — strips a file, removing the contents of any sections that wouldn't be stripped by --strip-debug, and leaves 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. 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. Main character tooling behaviour, honestly.

Okay bestie, let's finish this masterpiece. We are so close to being done and honestly? This is the part where the magic happens. Periodt. ✨

---

The intention is that this option will be used in conjunction with --add-gnu-debuglink to create a two part executable, okay? One is a stripped binary that 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 is 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 — Remove 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. It's giving compiler efficiency, bestie. ✨
• --extract-dwo — Extract the contents of all DWARF .dwo sections. See the --strip-dwo option for more information. It's the twin sister of --strip-dwo, lowkey iconic. 🎀
• --file-alignment num — Specify 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.] Get that alignment right, no cap. 💅
• --heap reserve and --heap reserve,commit — Specify 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.] Heap vibes only. 🔥
• --image-base value — Use 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.] Unique basing is the main character energy we deserve. 🌈
• --section-alignment num — Sets the section alignment. Sections in memory will always begin at addresses which are a multiple of this number. Defaults to 0x1000. [This option is specific to PE targets.] Alignment is self-care. 🦋
• --stack reserve and --stack reserve,commit — Specify 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.] Stack it up, bestie. 🥞
• --subsystem which, --subsystem which:major, and --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.] Choose your fighter, I mean subsystem. 👑
• --extract-symbol — Keep the file's section flags and symbols but remove all section data. Specifically, the option:
  • removes the contents of all sections;
  • sets the size of every section to zero; and
  • 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. It's the ultimate glow-down for sections. 💀

• --compress-debug-sections — Compress 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 love a self-aware compression algorithm. 🫶
• --compress-debug-sections=none, --compress-debug-sections=zlib, --compress-debug-sections=zlib-gnu, and --compress-debug-sections=zlib-gabi — 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 zlib. The debug sections are renamed to begin with .zdebug instead of .debug. Note - if compression would actually make a section larger, then it is not compressed nor renamed. The versatility is honestly iconic. 💅
• --decompress-debug-sections — Decompress DWARF debug sections using zlib. The original section names of the compressed sections are restored. Uncompress and slay. 🦋
• --elf-stt-common=yes and --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. Choose your symbol type, bestie. ✨
• --merge-notes and --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. Reduce, reuse, recycle those notes. 🌸
• -V and --version — Show the version number of objcopy. I gotta know what I'm working with. 👑
• -v and --verbose — Verbose output: list all object files modified. In the case of archives, objcopy -V lists all members of the archive. Tell me everything, I'm nosy. 💖
• --help — Show a summary of the options to objcopy. Your personal cheat sheet. 🎀
• --info — Display a list showing all architectures and object formats available. The full menu, okay? 🍓
• @file — Read 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. It's giving inception, but for command-line arguments. 🔥

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🌈 SEE ALSO 🌈

ld(1), objdump(1), and the Info entries for binutils. Go read those too, bestie, for the full lore. 📚

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👑 COPYRIGHT 👑

Copyright (c) 1991-2018 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, 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". Respect the license, it's literally the law. 💜

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And that's the whole manual, bestie! We did it! 🎉 This was binutils-2.30 from 2018-01-27. Now go forth and objcopy with confidence. You're literally a binary manipulation icon now. 💅✨