[ clisp-Bugs-1779490 ] linux:dirent definition error

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Bugs item #1779490, was opened at 2007-08-22 10:59
Message generated for change (Comment added) made by sds
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Category: ffi
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Aurelio Bignoli (abignoli)
Assigned to: Jörg Höhle (hoehle)
Summary: linux:dirent definition error

Initial Comment:
Field D_OFF of LINUX:DIRENT structure has wrong type.

Test case:

CL-USER> (linux:opendir "/tmp")
#<FOREIGN-ADDRESS #x08217808>
CL-USER> (linux:readdir *)
#S(LINUX:dirent :D_INO 2 :D_OFF 0 :D_RECLEN 2 :D_TYPE 0 :D_NAME "")
CL-USER> (type-of linux:dirent-d_off *)
; Evaluation aborted.
CL-USER> (type-of (linux:dirent-d_off *))
BIT
CL-USER> 

Field D_OFF should have type long.

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>Comment By: Sam Steingold (sds)
Date: 2007-08-23 18:18

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OK, I committed a large patch that allows (def-c-type size_t) without
specifying the actual size.
this does NOT fix dirent for some reason, but I added dirent64 and
readdir64, and they DO work.
I am not closing the bug, but I am out of my depth here - Joerg, could you
please fix it?

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Comment By: Sam Steingold (sds)
Date: 2007-08-23 15:44

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what's even more confusing is that odd_t and ino_t are really 64 bit:
sizeof(dirent)=276
offsetof(dirent,d_ino)=0
offsetof(dirent,d_off)=8
offsetof(dirent,d_reclen)=16
offsetof(dirent,d_type)=18
offsetof(dirent,d_name)=19
sizeof(dirent.d_ino)=8
sizeof(dirent.d_off)=8
sizeof(dirent.d_reclen)=2
sizeof(dirent.d_type)=1
sizeof(dirent.d_name)=256
but 
(def-c-struct my-dirent64
  (d_ino uint64)
  (d_off uint64)
  (d_reclen ushort)
  (d_type uchar)
  (d_name (c-array-max character 256)))
generates garbage, even though its size is "correct":
(sizeof 'linux:dirent)
268 ;
4
(sizeof 'MY-DIRENT)
268 ;
4
(sizeof 'MY-DIRENT64)
276 ;
4

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Comment By: Sam Steingold (sds)
Date: 2007-08-23 13:13

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Joerg, I have a patch that should make it work (but does not...)
basically, I allow (def-c-type foo) to mean "foo is an int type - figure
out its size and sign at compile time". then (def-c-type off_t) will figure
out whether off_t  is 64 bit or 32 bit at compile time.
alas, something is wrong: in convert_from_foreign, *(struct dirent*)data
prints TRT with the patch, but the function returns garbage, while with the
explicit (def-c-struct my-dirent
  (d_ino long)
  (d_off long)
  (d_reclen ushort)
  (d_type uchar)
  (d_name (c-array-max character 256)))

*(struct dirent*)data prints garbage, but the lisp function return TRT.
I attach the gdb sessions.
any suggestions?

File Added: gdb.log

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Comment By: Jörg Höhle (hoehle)
Date: 2007-08-23 12:51

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On my Ubuntu Daper 32bit box /usr/include/bits/dirent.h contains:
struct dirent
  {
#ifndef __USE_FILE_OFFSET64
    __ino_t d_ino;
    __off_t d_off;
#else
    __ino64_t d_ino;
    __off64_t d_off;
#endif
    unsigned short int d_reclen;
    unsigned char d_type;
    char d_name[256];		/* We must not include limits.h! */
  };
I have no idea whether __USE_FILE_OFFSET64 is defined on my box. But that
does not matter.
What's worse is that I have no idea how to reproduce the above #ifdef in
the Lisp code of modules/bindings/linux.lisp so that the correct def is
chosen on all platforms.

... My Ubuntu Dapper 32bit Intel centrino system apparently requires 64bit
defs.
readdir yields proper results only with s/uint64 type definitions.
_USE_FILE_OFFSET64 is defined in /usr/include/features.h based on other
defines from an unknown location.

So how to let Lisp know the proper definitions? Or work around the problem
differently?

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Comment By: Sam Steingold (sds)
Date: 2007-08-22 17:41

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actually, type-of return the type of the value, not the type of the slot.
it's BIT because that's the type of 0.
it's not clear to me what is going on: your code works and indicates that
d_off and d_ino are 32-bit, 
while gdb appears to think they are 64 bit each.

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Comment By: Sam Steingold (sds)
Date: 2007-08-22 11:36

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<http://permalink.gmane.org/gmane.lisp.clisp.general/11913>
<http://permalink.gmane.org/gmane.lisp.clisp.general/11917>

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