objcopy

Copy the contents of one object file to another (GNU)

Syntax:

objcopy [ -F bfdname ]
        [ -I bfdname ]
        [ -O bfdname ]
        [ -S ]  [ -g ]
        [ -K symbolname ]
        [ -N symbolname ]
        [ -L symbolname ]
        [ -W symbolname ]
        [ -x ]  [ -X ]
        [ -b n ]
        [ -i interleave ]
        [ -R sectionname ]
        [ -p ] [ --debugging ]
        [ --gap-fill=val ] [ --pad-to=address ]
        [ --set-start=val ] [ --adjust-start=incr ]
        [ --adjust-vma=incr ]
        [ --adjust-section-vma=section{=,+,-}val ]
        [ --adjust-warnings ]
        [ --no-adjust-warnings ]
        [ --set-section-flags=section=flags ]
        [ --add-section=sectionname=filename ]
        [ --change-leading-char ]
        [ --remove-leading-char ]
        [ --weaken ]
        [ -v ] [ -V ]  [ --help ]
        infile [outfile]

Options:

-b n

Keep only every nth byte of the input file (header data isn't affected). The n argument can be in the range from 0 to interleave-1, where interleave is given by the -i option or is the default of 4. This option is useful for creating files to program ROM. It's typically used with an srec output target.

-F bfdname

Use bfdname as the object format for both the input and the output file; that is, simply transfer data from source to destination with no translation. For more information, see "Target Selection" in the appendix Selecting the Target System.

-g

Don't copy debugging symbols from the source file.

-I bfdname

Consider the source file's object format to be bfdname, rather than attempt to deduce it. For more information, see "Target Selection" in the appendix Selecting the Target System.

-i interleave

Copy only one out of every interleave bytes. Select which byte to copy with the -b option. The default is 4. The objcopy utility ignores this option if you don't specify -b.

-K symbolname

Copy only symbol symbolname from the source file. This option may be given more than once.

-L symbolname

Make symbol symbolname local to the file, so that it isn't visible externally. This option may be given more than once.

-N symbolname

Don't copy symbol symbolname from the source file. This option may be given more than once.

-O bfdname

Write the output file using the object format bfdname. For more information, see "Target Selection" in the appendix Selecting the Target System.

-p

Set the access and modification dates of the output file to be the same as those of the input file.

-R sectionname

Remove any section named sectionname from the output file. This option may be given more than once. Note that using this option inappropriately may make the output file unusable.

-S

Don't copy relocation and symbol information from the source file.

-V

Show the version number of objcopy.

-v

Verbose output: list all object files modified. In the case of archives, objcopy -v lists all members of the archive.

-W symbolname

Make symbol symbolname weak. This option may be given more than once.

-X

Don't copy compiler-generated local symbols. (These usually start with L or a period.)

-x

Don't copy nonglobal symbols from the source file.

GNU extensions

--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 is the size of the file. This option works only on file formats that can support sections with arbitrary names.

--adjust-section-vma section{=,+,-}val

Set or adjust the address of the named section. 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 --adjust-vma. If section doesn't exist in the input file, a warning is issued, unless --no-adjust-warnings is used.

--adjust-start incr

Adjust the start address by adding incr. Not all object file formats support setting the start address.

--adjust-vma incr

Adjust the address of all sections, as well as the start address, by adding incr. Some object file formats don't permit section addresses to be changed arbitrarily. Note that this doesn't 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.

--adjust-warnings

If --adjust-section-vma is used, and the named section doesn't exist, issue a warning. This is the default.

--change-leading-char

Some object file formats use special characters at the start of symbols. The most common such character is underscore, which compilers often add before every symbol. This option tells objcopy to change the leading character of every symbol when it converts between object file formats. If the object file formats use the same leading character, this option has no effect. Otherwise, it adds, removes, or changes a character as appropriate.

--debugging

Convert debugging information, if possible. This isn't the default because only certain debugging formats are supported, and the conversion process can be time-consuming.

--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.

--help

Show a summary of the options to objcopy.

--no-adjust-warnings

Don't issue a warning if --adjust-section-vma is used, even if the named section doesn't exist.

--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).

--remove-leading-char

If the first character of a global symbol is a special symbol leading character used by the object file format, remove the character. The most common symbol leading character is underscore. This option removes a leading underscore from all global symbols.

This can be useful if you want to link together objects of different file formats with different conventions for symbol names. This option is different than --change-leading-char because it always changes the symbol name when appropriate, regardless of the object file format of the output file.

--set-section-flags section=flags

Set the flags for the named section. The flags argument is a comma-separated string of flag names. The recognized names are alloc, contents, load, readonly, code, data, and rom. You can set the contents flag for a section that doesn't have contents, but it isn't meaningful to clear the contents flag of a section that does have contents -- just remove the section instead. Not all flags are meaningful for all object file formats.

--set-start val

Set the address of the new file to val. Not all object file formats support setting the start address.

--strip-unneeded

Strip all symbols that aren't needed for relocation processing.

--weaken

Change all global symbols in the file to be weak. This can be useful when building an object that's linked against other objects using the -R option to the linker. This option is effective only when using an object file format that supports weak symbols.

Description:

The GNU objcopy utility copies the contents of one object file, infile, to another, outfile. The objcopy utility 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.

This utility creates temporary files to do its translations and deletes them afterward. objcopy 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. See "BFD" in Using LD in the full online GNU documentation.

You can use objcopy to generate S-records by specifying an output target of srec (e.g. use -O srec).

You can use objcopy to generate a raw binary file by specifying an output target of binary (e.g. use -O binary). When objcopy generates a raw binary file, it essentially produces a memory dump of the contents of the input object file. All symbols and relocation information are discarded. The memory dump starts at the load address of the lowest section copied into the output file.

When generating an S-record or a raw binary file, you may want to use -S to remove sections containing debugging information. In some cases, -R is useful to remove sections that contain information that isn't needed by the binary file.

If you don't specify outfile, objcopy creates a temporary file and destructively renames the result with the name of infile.

Author:

GNU

See also:

objdump