Re: [tor-bugs] #12387 [Tor bundles/installation]: (Some) Pluggable Transport binaries are not stripped

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#12387: (Some) Pluggable Transport binaries are not stripped
-------------------------------------+-------------------------------------
     Reporter:  gk                   |      Owner:  erinn
         Type:  defect               |     Status:  new
     Priority:  normal               |  Milestone:
    Component:  Tor                  |    Version:
  bundles/installation               |   Keywords:  TorBrowserTeam201407,
   Resolution:                       |  tbb-testcase
Actual Points:                       |  Parent ID:
       Points:                       |
-------------------------------------+-------------------------------------

Comment (by dcf):

 Replying to [comment:5 dcf]:
 > Replying to [comment:4 dcf]:
 > > Specifically for Go programs, "[https://donatstudios.com/Golang-
 Binary-Sizes#Comment23795 it isn't supported, isn't tested and is known to
 produce broken executables.]" I don't know exactly what the problem is,
 but we should check it out before trying to strip Go programs. I heard
 that Yawning has been stripping obfs4 without ill effects.
 > >  * [https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=717172 Debian
 #717172 - Stripping golang binaries causes crashes]
 > >  * [https://bugs.launchpad.net/ubuntu/+source/golang/+bug/1200255
 Ubuntu #1200255 - go get ... fails with SIGILL on armhf]
 >
 > According to the lantern-devel mailing list,
 "[https://groups.google.com/forum/#!topic/lantern-devel/FUN00B8rZtQ
 Compiling Go binaries with the -w linker flag makes binaries quite a bit
 smaller]." `-w` is "omit the DWARF symbol table." Additionally `-s` ("omit
 the symbol table and debug information") looks useful among the
 [http://golang.org/cmd/ld/ ld options].

 Here are tests using go1.3 on linux64. Summary: `-s` implies `-w'; and
 `-s` saves a lot, as much as `strip` does.

 {{{
 go build
 6.1M meek-client
 2.8M meek-client-torbrowser

 go build -ldflags '-w'
 4.7M meek-client
 2.2M meek-client-torbrowser

 go build -ldflags '-s'
 4.4M meek-client
 2.0M meek-client-torbrowser

 go build -ldflags '-s -w'
 4.4M meek-client
 2.0M meek-client-torbrowser

 go build && strip
 4.4M meek-client
 2.0M meek-client-torbrowser
 }}}

 It looks like we only have to use `-s`, because `-s` mostly implies `-w`.
 In the linker, the primary functions that check the `-w` option...
 https://code.google.com/p/go/source/browse/src/cmd/ld/dwarf.c?name=6bdbf9086c00#2163
   {{{
 void
 dwarfaddshstrings(LSym *shstrtab)
 {
         if(debug['w'])  // disable dwarf
                 return;
   }}}
 https://code.google.com/p/go/source/browse/src/cmd/ld/dwarf.c?name=6bdbf9086c00#2344
   {{{
 void
 dwarfaddmachoheaders(void)
 {
         MachoSect *msect;
         MachoSeg *ms;
         vlong fakestart;
         int nsect;

         if(debug['w'])  // disable dwarf
                 return;
   }}}
 https://code.google.com/p/go/source/browse/src/cmd/ld/dwarf.c?name=6bdbf9086c00#2435
   {{{
 void
 dwarfaddpeheaders(void)
 {
         if(debug['w'])  // disable dwarf
                 return;
   }}}
 ...are also gated on the outside by `-s`. There are a few other places
 where `-w` is checked that aren't so gated, but it appears they don't
 matter much for file size.
 https://code.google.com/p/go/source/browse/src/cmd/ld/elf.c?name=6bdbf9086c00#963
   {{{
         if(!debug['s']) {
                 addstring(shstrtab, ".symtab");
                 addstring(shstrtab, ".strtab");
                 dwarfaddshstrings(shstrtab);
         }
   }}}
 https://code.google.com/p/go/source/browse/src/cmd/ld/macho.c?name=6bdbf9086c00#478
   {{{
         if(!debug['s'] && linkmode != LinkExternal)
                 dwarfaddmachoheaders();
   }}}
 https://code.google.com/p/go/source/browse/src/cmd/ld/pe.c?name=6bdbf9086c00#639
   {{{
         if(!debug['s'])
                 dwarfaddpeheaders();
   }}}

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12387#comment:7>
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