[Toybox] [landley/toybox] Help building toybox with the NDK/bionic (#43)

[Rob Landley]

On 12/18/2016 12:52 PM, enh wrote:
> for configure-like usage you'll need to generate a standalone toolchain:
> 
>   https://developer.android.com/ndk/guides/standalone_toolchain.html
> 
> (you'll also want to use --unified-headers when you generate your
> standalone toolchain to get headers new enough to have any chance of
> being useful.)

I did that and got further. Starting with:

$ CROSS_COMPILE=/opt/android/x86_64/bin/x86_64-linux-android- \
  LDFLAGS=--static make defconfig

(Yes you have to run the config stage with the same CROSS_COMPILE and
LDFLAGS you're going to build with, or else it'll make a
generated/Config.probed that thinks TOYBOX_SHADOW should be switched on
when your toolchain hasn't got it, and so on.)

Then I did:

$ CROSS_COMPILE=/opt/android/x86_64/bin/x86_64-linux-android- \
  LDFLAGS=--static make

And it went:

In file included from ./toys.h:9:0,
                 from lib/args.c:12:
./lib/portability.h:274:33: fatal error: cutils/sched_policy.h: No such
file or directory
 #include <cutils/sched_policy.h>
                                 ^
I can add another compile-time probe for this, but I'm wondering if
there's a way to figure it out from the #defines? You added it in commit
e0dbc6beaf37:

+#ifdef __ANDROID__
+#include <cutils/sched_policy.h>
+#else
+typedef int SchedPolicy;
+int get_sched_policy(int tid, SchedPolicy *policy);
+const char *get_sched_policy_name(SchedPolicy policy);
+#endif

So presumably you understand when it is/isn't there? Anyway, when I #if
0'd that out, it got further but then died with:

toys/android/getprop.c:20:31: fatal error: cutils/properties.h: No such
file or directory
 #include <cutils/properties.h>

I'm guessing that was the libselinux thing you were talking about,
maybe? Anyway, I can switch that app off. Then it died with:

In file included from ./toys.h:9:0,
                 from toys/android/log.c:22:
./lib/portability.h:13:18: error: expected ')' before '__attribute__'
 #define noreturn __attribute__((noreturn))
In file included from toys/android/log.c:23:0:
/opt/android/x86_64/sysroot/usr/include/android/log.h:119:30: error:
expected ',' or ';' before ')' token
     __attribute__ ((noreturn))

Which is really _weird_ but it seems like android/log.h #defining
noreturn reaches back in time and breaks the earlier #define of
noreturn? Or something? (gcc is weird.) Anyway, switching off the "log"
command as well... And in addition to getprop, I have to switch off
setprop, start, and stop because they all #include <cutils/properties.h>
which isn't there.

Then it made it through several commands, but the "eject" command died
because:
toys/other/eject.c:25:21: fatal error: scsi/sg.h: No such file or directory
 #include <scsi/sg.h>

Which is a linux-kernel header, but I can't say I'm hugely surprised.
Switch that off...

And it's doing pretty well through the rest of the commands. Lots of
warnings about implicit declarations (gethostid, crypt) wandering by. I
wonder if I can -Werror just _that_ error? (That's going to come back
and bite me at link time, I just know it...)

Yes. Yes it is:

generated/obj/lib_lib.o:lib.c:function verror_msg: error: undefined
reference to 'stderr'
generated/obj/lib_lib.o:lib.c:function help_exit: error: undefined
reference to 'stderr'
generated/obj/lib_lib.o:lib.c:function mkpathat: error: undefined
reference to 'stderr'
generated/obj/lib_lib.o:lib.c:function yesno: error: undefined reference
to 'stderr'
generated/obj/lib_lib.o:lib.c:function yesno: error: undefined reference
to 'stdin'
generated/obj/lib_lib.o:lib.c:function bufgetgrgid: error: undefined
reference to 'getgrgid_r'
generated/obj/lib_lib.o:lib.c:function do_lines: error: undefined
reference to 'stdin'
generated/obj/lib_linestack.o:linestack.c:function draw_trim_esc: error:
undefined reference to 'stdout'
generated/obj/lib_xwrap.o:xwrap.c:function xexit: error: undefined
reference to 'stdout'
generated/obj/lib_xwrap.o:xwrap.c:function xprintf: error: undefined
reference to 'stdout'
generated/obj/lib_xwrap.o:xwrap.c:function xputs: error: undefined
reference to 'stdout'
generated/obj/hostname.o:hostname.c:function hostname_main: error:
undefined reference to 'sethostname'
generated/obj/md5sum.o:md5sum.c:function looplines: error: undefined
reference to 'stdin'
generated/obj/md5sum.o:md5sum.c:function looplines: error: undefined
reference to 'stdin'
generated/obj/hostid.o:hostid.c:function hostid_main: error: undefined
reference to 'gethostid'
generated/obj/mkpasswd.o:mkpasswd.c:function mkpasswd_main: error:
undefined reference to 'crypt'
collect2: error: ld returned 1 exit status

So it couldn't find stderr, stdin, stdout, getgrid_r, gethostid, and
crypt. Well that's a _manageable_ list, but the stdin/stdout/stderr
stuff I can't easily patch around, that's posix:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/stdout.html

I'm assuming that AOSP had stdin/stdout/stderr. You can't error_exit()
without verror_msg(), it's in pretty much every command. (I think if you
build "false" standalone, it might get omitted... "make false", "objdump
-d generated/unstripped/false | less"... Nope, it's still there.
Probably shouldn't be. I'll throw it on the todo heap.) *

I don't see a strong reason _not_ to have a gethostid(), but I could
stub it out (or just do the syscall, or read /proc/sys/kernel/hostname)
if you have one.

I can also probe/stub out getgrid_r() and crypt() which both fall under
"do we have /etc/passwd or similar on this system". It would be nice if
there was some sort of plan for setting up a "posix container" under
android that understood 2 users (root and not root) so we can run AOSP
builds as "not root", but that's a todo item. In the meantime consistent
stubs would be nice. :)

Rob

* Ah, it's because everything except true and false has --help output, and:

  ./echo --help > /dev/full
  echo: write: No space left on device

That's why error_exit doesn't drop out. But I should probably let it do
so when you've disabled CONFIG_TOYBOX_HELP_DASHDASH.