Kevin Ryde <[EMAIL PROTECTED]> writes:
> Looks about right. What's the child process doing? It's supposed to
> be writing to the parent to say continue. (Unless it failed to fork
> there should be some child, either running or a zombie.)
(Consider the following info preliminary. I haven't had any time to
try and figure out the actual cause, but since I just discovered this,
and I have to stop for the moment, I wanted to let everyone else have
a look.)
After further investigation, it appears that particular child might
not be running, at least not on some of the runs. I switched back to
the original code (the code that would hang), added some debug
statements, ran strace -p -s 100, etc. on "make check", and found that
the child appears to be segfaulting at least some of the time here (in
popen.scm):
(port-for-each (lambda (pt-entry)
;;(dbg-out (list 'pt-entry pt-entry))
(false-if-exception
(let ((pt-fileno (fileno pt-entry)))
(if (not (or (= pt-fileno input-fdes)
(= pt-fileno output-fdes)
(= pt-fileno error-fdes)))
(close-fdes pt-fileno))))))
When I uncomment the dbg-out statement above (which just writes the
arg and a newline to an output-port and then forces the output), I see
this on the console:
ERROR: popen.test: open-output-pipe: no duplicate - arguments:
((wrong-type-arg "list-copy" "Wrong type argument in position ~A: ~S"
(1 (pt-entry . #<freed cell 0x40305830; GC missed a reference>))
((pt-entry . #<freed cell 0x40305830; GC missed a reference>))))
this in the dbg-out output file:
...
(pt-entry #<output: string 81079e0>)
(pt-entry #<output: string 8106650>)
(pt-entry #<freed cell 0x40643c18; GC missed a reference>)
and this in the strace (1402 is the forked child process):
1402 write(7, "ERROR: popen.test: open-output-pipe: no duplicate -
arguments: ((wrong-type-arg \"list-copy\" \"Wrong t"..., 263) = -1 EBADF (Bad
file descriptor)
1402 write(2, "ERROR", 5) = -1 EBADF (Bad file descriptor)
1402 write(2, "\nException during displaying of ", 32) = -1 EBADF (Bad file
descriptor)
1402 write(7, "ERROR: popen.test: open-output-pipe: no duplicate -
arguments: ((wrong-type-arg \"list-copy\" \"Wrong t"..., 263) = -1 EBADF (Bad
file descriptor)
1402 write(2, "ERROR", 5) = -1 EBADF (Bad file descriptor)
1402 write(2, "\nException during displaying of ", 32) = -1 EBADF (Bad file
descriptor)
1402 exit_group(1) = ?
If I omit the dbg-out statement in the above code, then I can just see
the child die due to a SEGV in the strace log (2126 is the child):
2126 close(12 <unfinished ...>
2123 <... close resumed> ) = 0
2126 <... close resumed> ) = 0
2123 access("/etc/ld.so.nohwcap", F_OK <unfinished ...>
2126 close(10 <unfinished ...>
2123 <... access resumed> ) = -1 ENOENT (No such file or
directory)
2126 <... close resumed> ) = 0
2123 open("/lib/tls/i686/cmov/libdl.so.2", O_RDONLY <unfinished ...>
2126 close(29 <unfinished ...>
2123 <... open resumed> ) = 5
2126 <... close resumed> ) = 0
2123 read(5, <unfinished ...>
2126 --- SIGSEGV (Segmentation fault) @ 0 (0) ---
So I started from a clean tree, enabled core dumps, and here's what
gdb had to say about the resulting core:
Program terminated with signal 11, Segmentation fault.
#0 0x400729ca in scm_fileno (port=0x0) at ioext.c:180
180 port = SCM_COERCE_OUTPORT (port);
(gdb) where
#0 0x400729ca in scm_fileno (port=0x0) at ioext.c:180
#1 0x4005ad41 in ceval (x=0x404, env=0x40372710) at eval.c:4218
#2 0x4005b26e in ceval (x=<value optimized out>, env=0x40372710)
at eval.c:3634
In any case, as I said, consider all this preliminary. For everything
but the core dump, I wasn't working from a clean tree.
--
Rob Browning
rlb @defaultvalue.org and @debian.org; previously @cs.utexas.edu
GPG starting 2002-11-03 = 14DD 432F AE39 534D B592 F9A0 25C8 D377 8C7E 73A4
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