Re: On darwin, diff <(echo ab) <(echo cd) does nothing

[Vincent Lefevre]

On 2005-08-20 15:16:10 -0700, Paul Eggert wrote:
> Vincent Lefevre <address@hidden> writes:
> 
> > On my Mac OS X 10.4.2 (Tiger) machine, with zsh and diff 2.8.1:
> >
> > prunille:~> diff <(echo ab) <(echo cd)
> > prunille:~> 

If I put "cd\n" in a file, I sometimes get the result as expected:

prunille:~> diff <(echo ab) <(cat file)
prunille:~> diff <(echo ab) <(cat file)
prunille:~> diff <(echo ab) <(cat file)
1c1
< ab
---
> cd
zsh: exit 1     diff <(echo ab) <(cat file)

If I use ktrace, the diff always gives nothing. But if the file
contains a second line, the diff works.

A buffer problem or something related to a fd being closed too soon?

> Can you trace "diff" (using ktrace? sorry, I don't use Mac OS X so you
> may have to look this up yourself) to see what system calls that
> "diff" is executing?

kdump -m 16 gives with file containing only a line "cd":

 28804 ktrace   RET   ktrace 0
 28804 ktrace   CALL  execve(0xbfffe5cc,0xbfffeb9c,0xbfffebac)
 28804 ktrace   NAMI  "/Users/vinc17/bin/diff"
 28804 ktrace   RET   execve -1 errno 2 No such file or directory
 28804 ktrace   CALL  execve(0xbfffe5cc,0xbfffeb9c,0xbfffebac)
 28804 ktrace   NAMI  "/usr/local/bin/diff"
 28804 ktrace   RET   execve -1 errno 2 No such file or directory
 28804 ktrace   CALL  execve(0xbfffe5cc,0xbfffeb9c,0xbfffebac)
 28804 ktrace   NAMI  "/opt/local/bin/diff"
 28804 ktrace   RET   execve -1 errno 2 No such file or directory
 28804 ktrace   CALL  execve(0xbfffe5cc,0xbfffeb9c,0xbfffebac)
 28804 ktrace   NAMI  "/usr/bin/diff"
 28804 ktrace   NAMI  "/usr/lib/dyld"
 28804 diff     RET   execve 0
 28804 diff     CALL  getuid
 28804 diff     RET   getuid 501/0x1f5
 28804 diff     CALL  getuid
 28804 diff     RET   getuid 501/0x1f5
 28804 diff     CALL  geteuid
 28804 diff     RET   geteuid 501/0x1f5
 28804 diff     CALL  getgid
 28804 diff     RET   getgid 501/0x1f5
 28804 diff     CALL  getegid
 28804 diff     RET   getegid 501/0x1f5
 28804 diff     CALL  
__sysctl(0xbfffe66c,0x2,0xbfffe674,0xbfffe668,0x8fe49ecc,0xa)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  __sysctl(0xbfffe674,0x2,0x8fe5885c,0xbfffe718,0,0)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  
__sysctl(0xbfffe66c,0x2,0xbfffe674,0xbfffe668,0x8fe49ef8,0xd)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  __sysctl(0xbfffe674,0x2,0x8fe58858,0xbfffe718,0,0)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  open(0x14e8,0,0)
 28804 diff     NAMI  "/usr/lib/libSystem.B.dylib"
 28804 diff     RET   open 3
 28804 diff     CALL  fstat(0x3,0xbfffc63c)
 28804 diff     RET   fstat 0
 28804 diff     CALL  pread(0x3,0xbfffca9c,0x1000,0)
 28804 diff     GIO   fd 3 read 4096 bytes
       "Êþº¾\0\0\0\^B\0\0\0\^R\0\0\0\0"
 28804 diff     RET   pread 4096/0x1000
 28804 diff     CALL  pread(0x3,0xbfffca9c,0x1000,0x1000)
 28804 diff     GIO   fd 3 read 4096 bytes
       "þíúÎ\0\0\0\^R\0\0\0\0\0\0\0\^F"
 28804 diff     RET   pread 4096/0x1000
 28804 diff     CALL  __sysctl(0xbfffbcd0,0x2,0xbfffbcc8,0xbfffbccc,0,0)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  shared_region_map_file_np(0x3,0x4,0xbfffbbb0,0)
 28804 diff     RET   shared_region_map_file_np 0
 28804 diff     CALL  close(0x3)
 28804 diff     RET   close 0
 28804 diff     CALL  open(0x9000072c,0,0)
 28804 diff     NAMI  "/usr/lib/system/libmathCommon.A.dylib"
 28804 diff     RET   open 3
 28804 diff     CALL  fstat(0x3,0xbfffc59c)
 28804 diff     RET   fstat 0
 28804 diff     CALL  pread(0x3,0xbfffc9fc,0x1000,0)
 28804 diff     GIO   fd 3 read 4096 bytes
       "Êþº¾\0\0\0\^B\0\0\0\^R\0\0\0\0"
 28804 diff     RET   pread 4096/0x1000
 28804 diff     CALL  pread(0x3,0xbfffc9fc,0x1000,0x1000)
 28804 diff     GIO   fd 3 read 4096 bytes
       "þíúÎ\0\0\0\^R\0\0\0\0\0\0\0\^F"
 28804 diff     RET   pread 4096/0x1000
 28804 diff     CALL  shared_region_map_file_np(0x3,0x3,0xbfffbeb0,0)
 28804 diff     RET   shared_region_map_file_np 0
 28804 diff     CALL  close(0x3)
 28804 diff     RET   close 0
 28804 diff     CALL  __sysctl(0xbfffea6c,0x2,0xbfffea68,0xbfffea60,0,0)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  __sysctl(0xbfffea6c,0x2,0xbfffea64,0xbfffea60,0,0)
 28804 diff     RET   __sysctl 0
 28804 diff     CALL  open(0xbfffe578,0,0x1b6)
 28804 diff     NAMI  "/usr/share/locale/en_US.ISO8859-1/LC_CTYPE"
 28804 diff     RET   open 3
 28804 diff     CALL  fstat(0x3,0xbfffe4b8)
 28804 diff     RET   fstat 0
 28804 diff     CALL  fstat(0x3,0xbfffe2c8)
 28804 diff     RET   fstat 0
 28804 diff     CALL  lseek(0x3,0,0x1)
 28804 diff     RET   lseek 0
 28804 diff     CALL  lseek(0x3,0,0)
 28804 diff     RET   lseek 0
 28804 diff     CALL  read(0x3,0x1801200,0x1000)
 28804 diff     GIO   fd 3 read 3196 bytes
       "RuneMagiNONE\0\0\0\0"
 28804 diff     RET   read 3196/0xc7c
 28804 diff     CALL  close(0x3)
 28804 diff     RET   close 0
 28804 diff     CALL  stat(0xbfffecf1,0xbfffe8d8)
 28804 diff     NAMI  "/dev/fd/15"
 28804 diff     RET   stat 0
 28804 diff     CALL  stat(0xbfffecfc,0xbfffe98c)
 28804 diff     NAMI  "/dev/fd/16"
 28804 diff     RET   stat 0
 28804 diff     CALL  close(0x1)
 28804 diff     RET   close 0
 28804 diff     CALL  exit(0)

When adding a second line ".." to file, I get (after changing the
pid to 28804 as above, so that I could diff the kdump output) a few
differences like:

<  28804 ktrace   CALL  execve(0xbfffe5cc,0xbfffeb9c,0xbfffebac)
---
>  28804 ktrace   CALL  execve(0xbfffe5cc,0xbfffeba4,0xbfffebb4)

and the end is different:

[...]
 28804 diff     GIO   fd 3 read 3196 bytes
       "RuneMagiNONE\0\0\0\0"
 28804 diff     RET   read 3196/0xc7c
 28804 diff     CALL  close(0x3)
 28804 diff     RET   close 0
 28804 diff     CALL  stat(0xbfffed01,0xbfffe8d8)
 28804 diff     NAMI  "/dev/fd/15"
 28804 diff     RET   stat 0
 28804 diff     CALL  stat(0xbfffed0c,0xbfffe98c)
 28804 diff     NAMI  "/dev/fd/16"
 28804 diff     RET   stat 0
 28804 diff     CALL  open(0xbfffed01,0,0)
 28804 diff     NAMI  "/dev/fd/15"
 28804 diff     RET   open 3
 28804 diff     CALL  open(0xbfffed0c,0,0)
 28804 diff     NAMI  "/dev/fd/16"
 28804 diff     RET   open 4
 28804 diff     CALL  read(0x3,0x1802400,0x200)
 28804 diff     GIO   fd 3 read 3 bytes
       "ab
       "
 28804 diff     RET   read 3
 28804 diff     CALL  read(0x3,0x1802403,0x1fd)
 28804 diff     GIO   fd 3 read 0 bytes
       ""
 28804 diff     RET   read 0
 28804 diff     CALL  read(0x4,0x1802600,0x200)
 28804 diff     GIO   fd 4 read 6 bytes
       "cd
        ..
       "
[...]

> Possibly zsh on Mac OS X 10.4.2 is operating in an incompatible way.
> What version of zsh are you using?

zsh 4.2.5 (powerpc-apple-darwin8.2.0)

from the darwinports.

-- 
Vincent Lefèvre <address@hidden> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / SPACES project at LORIA