#3571: Bizzarely bloated binaries
-----------------------------+----------------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.10.4 | Severity: normal
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
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Compiling a trivial test program:
{{{
module Main where
main = print "Hello World"
}}}
Using GHC 6.10.4 produces a VERY suspicious PE file. (NB: this applies to
DLL as well as EXE output).
The two problems that I have observed are:
1) The PE always contains a .stab and .stabstr section totalling 0x2A00
of debug data. Looking at the contents of stabstr, this appears to
originate from a libffi object file. Perhaps we could disable stabs when
building libffi to remove this bloat from output binaries.
2) The PE contains *A LOT* of trailing junk. My hello world program is
691K, and the PE contains 0x4FAFC = 318K of data which doesn't live in any
section! Trimming this data appears to have no effect on the correctness
of the program! The amount of junk grows proportionally to the amount of
real code and data - I have observed e.g. 18Mb DLLs of which 9Mb are
trailing junk.
To repeat: we could potentially *halve* GHC binary sizes by fixing this
linker behaviour.
I'm not sure where exactly the fault lies - whether it is a GHC problem or
some bug in Ld.
To test trimming your executables and DLLs, you can use this utility I
whipped up. Usage is "trimpe <file1> ... <fileN>". It will trim useless
data from the end of the files in place:
{{{
{-# LANGUAGE ScopedTypeVariables #-}
module Main (main) where
import Control.Monad
import Data.Binary
import Data.Binary.Get
import qualified Data.ByteString.Lazy as ByteString
import Data.Word
import System.Environment
import Debug.Trace
assertM :: Monad m => Bool -> m ()
assertM True = return ()
assertM False = fail "assertM"
newtype PEImageLength = PEImageLength Word32
-- http://www.microsoft.com/whdc/system/platform/firmware/PECOFF.mspx
instance Binary PEImageLength where
get = do
-- Skip the MS DOS stub
skip 0x3c
pe_sig_offset <- getWord32le
-- Skip to the PE signature
skip (fromIntegral pe_sig_offset - (0x4 + 0x3c))
-- Read the PE signature itself
-- NB: this will always be the string "PE\0\0"
_sig <- getWord32le
assertM (_sig == 0x00004550)
-- Read COFF file header
_machine <- getWord16le
_no_of_sects <- getWord16le
_time_date_stamp <- getWord32le
_ptr_to_sym_tab <- getWord32le
_no_of_syms <- getWord32le
_size_of_opt_header <- getWord16le
assertM (_size_of_opt_header /= 0)
_characteristics <- getWord16le
-- Read the "optional" header
magic <- getWord16le
let pe32plus = magic == 0x20B
_maj_link_ver :: Word8 <- get
_min_link_ver :: Word8 <- get
_size_of_code <- getWord32le
_size_of_init_data <- getWord32le
_size_of_uninit_data <- getWord32le
_addr_of_entry_point <- getWord32le
_base_of_code <- getWord32le
when (not pe32plus) $ do _base_of_data <- getWord32le; return ()
-- Read the optional header Windows fields
if pe32plus
then do _image_base <- getWord64le; return ()
else do _image_base <- getWord32le; return ()
_sect_alignment <- getWord32le
_file_alignment <- getWord32le
_maj_os_version <- getWord16le
_min_os_version <- getWord16le
_maj_image_version <- getWord16le
_min_image_version <- getWord16le
_maj_subsys_version <- getWord16le
_min_subsys_version <- getWord16le
_win32_version <- getWord32le
size_of_image <- getWord32le
-- There is more stuff later, but I simply don't care about it
-- NB: we could trim a little more agressively if we interpreted
-- the sections as well...
return $ PEImageLength size_of_image
put = error "Binary PEImageLength: put"
main :: IO ()
main = do
files <- getArgs
forM_ files trimPEToImageSize
trimPEToImageSize :: FilePath -> IO ()
trimPEToImageSize file = do
putStrLn $ file
pe_contents <- ByteString.readFile file
let PEImageLength image_size = decode pe_contents
-- Force the file to close so that the write may succeed
(ByteString.last pe_contents) `seq` return ()
when (ByteString.length pe_contents > fromIntegral image_size) $ do
putStrLn $ "* Trimming to image size (" ++ show image_size ++ ")"
let pe_contents' = ByteString.take (fromIntegral image_size)
pe_contents
ByteString.writeFile file pe_contents'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3571>
GHC <http://www.haskell.org/ghc/>
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