DATE: 2018.11.13
1、参考
https://blog.csdn.net/qq_37858386/article/details/78559490
2、strip命令
strip作用：从目标文件或可执行文件中剥掉一些符号信息和调试信息，使文件变小。
man strip：
STRIP(1) GNU Development Tools STRIP(1)
NAME
strip - Discard symbols from object files.
SYNOPSIS
strip [-F bfdname |--target=bfdname]
[-I bfdname |--input-target=bfdname]
[-O bfdname |--output-target=bfdname]
[-s|--strip-all]
[-S|-g|-d|--strip-debug]
[--strip-dwo]
[-K symbolname |--keep-symbol=symbolname]
[-N symbolname |--strip-symbol=symbolname]
[-w|--wildcard]
[-x|--discard-all] [-X |--discard-locals]
[-R sectionname |--remove-section=sectionname]
[--remove-relocations=sectionpattern]
[-o file] [-p|--preserve-dates]
[-D|--enable-deterministic-archives]
[-U|--disable-deterministic-archives]
[--keep-file-symbols]
[--only-keep-debug]
[-v |--verbose] [-V|--version]
[--help] [--info]
objfile...
DESCRIPTION
GNU strip discards all symbols from object files objfile. The list of object files may
include archives. At least one object file must be given.
strip modifies the files named in its argument, rather than writing modified copies
under different names.
OPTIONS
-F bfdname
--target=bfdname
Treat the original objfile as a file with the object code format bfdname, and
rewrite it in the same format.
--help
Show a summary of the options to strip and exit.
--info
Display a list showing all architectures and object formats available.
-I bfdname
--input-target=bfdname
Treat the original objfile as a file with the object code format bfdname.
-O bfdname
--output-target=bfdname
Replace objfile with a file in the output format bfdname.
-R sectionname
--remove-section=sectionname
Remove any section named sectionname from the output file, in addition to whatever
sections would otherwise be removed. This option may be given more than once.
Note that using this option inappropriately may make the output file unusable. The
wildcard character * may be given at the end of sectionname. If so, then any
section starting with sectionname will be removed.
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 patter '.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
Remove all symbols.
-g
-S
-d
--strip-debug
Remove debugging symbols only.
--strip-dwo
Remove the contents of all DWARF .dwo sections, leaving the remaining debugging
sections and all symbols intact. See the description of this option in the objcopy
section for more information.
--strip-unneeded
Remove 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
Remove symbol symbolname from the source file. This option may be given more than
once, and may be combined with strip options other than -K.
-o file
Put the stripped output in file, rather than replacing the existing file. When
this argument is used, only one objfile argument may be specified.
-p
--preserve-dates
Preserve the access and modification dates of the file.
-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. 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.
-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 -K !foo -K fo*
would cause strip to only keep symbols that start with the letters "fo", but to
discard the symbol "foo".
-x
--discard-all
Remove non-global symbols.
-X
--discard-locals
Remove compiler-generated local symbols. (These usually start with L or ..)
--keep-file-symbols
When stripping a file, perhaps with --strip-debug or --strip-unneeded, retain any
symbols specifying source file names, which would otherwise get stripped.
--only-keep-debug
Strip a file, emptying the contents of any sections that would not be stripped by
--strip-debug and leaving the debugging sections intact. In ELF files, this
preserves all the note sections in the output as well.
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 a stripped binary which
will occupy less space in RAM and in a distribution and the second 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...
1.<Run "objcopy --only-keep-debug foo foo.dbg" to>
create a file containing the debugging info.
1.<Run "objcopy --strip-debug foo" to create a>
stripped executable.
1.<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.>
1.<Copy "foo" to "foo.full">
1.<Run "strip --strip-debug foo">
1.<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.
-V
--version
Show the version number for strip.
-v
--verbose
Verbose output: list all object files modified. In the case of archives, strip -v
lists all members of the archive.
@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.
3、实战
soaringlee@ubuntu:~/Desktop/codecs/libmpeg2-0.5.1/libmpeg2$ ls -laths decode.o
40K -rw-rw-r-- 1 soaringlee soaringlee 40K Oct 20 19:04 decode.o
soaringlee@ubuntu:~/Desktop/codecs/libmpeg2-0.5.1/libmpeg2$ file decode.o
decode.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
soaringlee@ubuntu:~/Desktop/codecs/libmpeg2-0.5.1/libmpeg2$ strip decode.o
soaringlee@ubuntu:~/Desktop/codecs/libmpeg2-0.5.1/libmpeg2$ ls -laths decode.o
8.0K -rw-rw-r-- 1 soaringlee soaringlee 4.8K Nov 13 05:37 decode.o
soaringlee@ubuntu:~/Desktop/codecs/libmpeg2-0.5.1/libmpeg2$ file decode.o
decode.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), stripped
对decode.o进行strip之后，decode.o的文件大小从40k减少为4.8k，一般not stripped的库用于调试，stripped的库用做发布版本release。通过nm命令可以查看目标文件是否含有符号。