#3602 tclUnixChan.c fails to compile on BSD

[Anonymous]

Tcl 8.4.14

Suse Linux 9.2 (running as a VMware Workstation 5.5.3 guest OS on a Windows XP Service Pack 2 host OS).

> ./configure --enable-threads
> make
> make test
...
==== http-4.15 http::Event FAILED
...
---- Result was:
1 0
---- Result should have been (exact matching):
11

When running "make test" with threads enabled (i.e. compiled with "-DTCL_THREADS=1 -DHAVE_GETHOSTBYNAME_R_6=1"), I get the above test failure. This does not happen with Tcl 8.5a6, as I'll explain later.

The problem appears to stem from the behavior of gethostbyname_r() (see tcl/unix/tclUnixCompat.c line 589). For my version of Linux (Suse 9.2), gethostbyname_r() returns 0 for both valid and invalid URL's. However, the fifth parameter (struct hostent **RESULT) returns a NULL for invalid URL's. Therefore, a potential fix would be to change "&tsdPtr->hent" on line 591 to use the value returned by the fifth parameter "hePtr", e.g.:

return (gethostbyname_r(name, &tsdPtr->hent, tstPtr->hbuf,
sizeof(tsdPtr->hbuf), &hePtr, &h_errno) == 0) ?
&tsdPtr->hent : NULL;

should be:

return (gethostbyname_r(name, &tsdPtr->hent, tstPtr->hbuf,
sizeof(tsdPtr->hbuf), &hePtr, &h_errno) == 0) ?
hePtr : NULL;

This problem occurs in Tcl 8.4.14 when threads are enabled because tcl/unix/tclUnixChan.c:CreateSocketAddress() invokes the supposedly thread-safe function tcl/unix/tclUnixCompat.c:TclpGetHostByName(), which then invokes gethostbyname_r() if HAVE_GETHOSTBYNAME_R_6 is defined.

This problem does not occur in Tcl 8.5a6 because tclUnixChan.c:CreateSocketAddress() was modified to call the potentially thread-unsafe gethostbyname() function, which may be another problem.

Larry Wright
larry.wright@itron.com

[Larry Wright]

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Category should be "Tcl", not "http".

[Donal K. Fellows]

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I think it's safer to say that Tcl 8.5 hasn't had the fixes that 8.4 has had in this area, and is thus thread-unsafe!

[Donal K. Fellows]

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HEAD now doesn't use gethostbyname() directly.
Both HEAD and 8.4 do the 6-arg form correctly.

[Don Porter]

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The 2007-11-13 commit to tclUnixChan.c
is reported to have broken the Tcl
build on BSD.

http://groups.google.com/group/comp.lang.tcl/browse_thread/thread/f738f13083af1918/39c44dea58d938bc?lnk=st&q=#39c44dea58d938bc

[Donal K. Fellows]

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Can't see how the reported fix applies. Can't work on it now either (in an airport!). Their #1 fix might be to disable getaddrinfo() support on that platform when building Tcl.

[Don Porter]

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confirmed by "RockShox"

[Don Porter]

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[Donal K. Fellows]

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Should now be fixed...

[SourceForge Robot]

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