elf size

[Kai Ruottu]

"Aaron J. Grier" wrote:
> 
> On Thu, Mar 14, 2002 at 02:54:53PM -0700, Jibin Han wrote:
> > I just built an ELF format executible by linking hello_world.o,
> > bsp archive and libc. The file size is around 300k even I use -o3 in
> > compile option. hello_world.c is trivial. Someone else ported libc
> > for powerpc eabi, and it seems no problem.

 Ever heard about someone debugging the produced executable at source-
level ?  Then the produced executable and also the C-library routines
may include quite a lot extra stuff called 'debug info'...
 
> you are calling printf, which references other code which must then be
> linked in from libc.

 Not strip'ing the debug info away from the resulted executable is the
most usual reason for very big executables. If one chooses to not debug
the C-libraries, they should be produced without the '-g' or strip'ed
afterwards with 'strip --strip-debug' (a plain vanilla 'strip' removes
all symbols from them, and in libraries these will be needed)...

---------------------------------- clip ----------------------------------------
E:\usr\local\ppc-eabi\bin>strip --help
Usage: strip <switches> in-file(s)
 The switches are:
<snip>
  -s --strip-all                   Remove all symbol and relocation information
  -g -S --strip-debug              Remove all debugging symbols
     --strip-unneeded              Remove all symbols not needed by relocations
<snip>
  -h --help                        Display this output
  -o <file>                        Place stripped output into <file>
strip: supported targets: elf32-powerpc aixcoff-rs6000 elf32-powerpcle ppcboot
elf32-little elf32-big srec symbolsrec tekhex binary ihex
Report bugs to bug-gnu-utils@gnu.org
---------------------------------- clip ----------------------------------------

 IMHO everybody should learn to write '<command> --help' for the GNU tools,
when needing any help for them, not handling others as 'walking manuals' ;-)

 A simple test with not-so-trivial 'test-tprintf' program gives (output
snipped) :

e:\usr\local\samples>gcc-ppc-eabi -myellowknife -Os -o tst_ppc-eabi.x tprintf.c

e:\usr\local\samples>dir tst_ppc-eabi.x

15.03.2002  11:06               74Â 672 tst_ppc-eabi.x

e:\usr\local\samples>\usr\local\ppc-eabi\bin\strip tst_ppc-eabi.x

e:\usr\local\samples>dir tst_ppc-eabi.x

15.03.2002  11:06               43Â 440 tst_ppc-eabi.x

e:\usr\local\samples>\usr\local\ppc-eabi\bin\size tst_ppc-eabi.x
   text    data     bss     dec     hex filename
  34080    5580       8   39668    9af4 tst_ppc-eabi.x

 So 30 k for a "Hello World" would be more expected with 'ppc-eabi' and
with some bsp-package / glue-library, not the 300 k ...

> > Is there any tool to help debuging that?

 Just check the situation with your C-libraries, the 'libc.a' I have has
a size of 365 kbytes, if yours is 3 Mbytes or such, it has still the debug
info in it... The 'libg.a' may include the debug info and '-g*' in the GCC
command line should trigger the linker using it. For any library where you
don't want any debug info any more, just run the following:

   powerpc-eabi-strip --strip-debug <libname>.a

for instance:

   powerpc-eabi-strip --strip-debug libc.a

in order to strip the debug info away. Taking backups first is of course
highly recommended...

Cheers, Kai


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