Bugs item #1888932, was opened at 2008-02-07 17:19
Message generated for change (Comment added) made by yangtse
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Category: debug/info output
Group: wrong behaviour
Status: Open
Resolution: Accepted
Priority: 5
Private: No
Submitted By: Patrick_ (patrick_)
Assigned to: Daniel Stenberg (bagder)
Summary: Error buffer not filled on CURLE_COULDNT_RESOLVE_HOST

Initial Comment:
With libcurl 7.17.1 and 7.18.0, when adding an easy handle (that has CURLOPT_ERRORBUFFER set) to a multi handle and "performing" the multi handle, if the error code received is CURLE_COULDNT_RESOLVE_HOST, the error buffer is not filled with the corresponding error message. When running the same easy handle with curl_easy_perform(), and the error received is CURLE_COULDNT_RESOLVE_HOST, the error buffer _is_ filled as expected.

Attached is standalone C code which demonstrates the bug.

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Comment By: Yang Tse (yangtse)
Date: 2008-02-09 05:02

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It seems that tis only affects Windows threaded name resolver builds.

Verify if this patch solves the issue for you.

Index: lib/hostthre.c
===================================================================
RCS file: /cvsroot/curl/curl/lib/hostthre.c,v
retrieving revision 1.50
diff -u -r1.50 hostthre.c
--- lib/hostthre.c 5 Nov 2007 09:45:09 -0000 1.50
+++ lib/hostthre.c 9 Feb 2008 04:08:01 -0000
@@ -682,6 +682,8 @@
 CURLcode Curl_is_resolved(struct connectdata *conn,
                           struct Curl_dns_entry **entry)
 {
+ struct SessionHandle *data = conn->data;
+
   *entry = NULL;
 
   if(conn->async.done) {
@@ -689,6 +691,8 @@
     Curl_destroy_thread_data(&conn->async);
     if(!conn->async.dns) {
       TRACE(("Curl_is_resolved(): CURLE_COULDNT_RESOLVE_HOST\n"));
+ failf(data, "Could not resolve host: %s; %s",
+ conn->host.name, Curl_strerror(conn, conn->async.status));
       return CURLE_COULDNT_RESOLVE_HOST;
     }
     *entry = conn->async.dns;

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Comment By: Daniel Stenberg (bagder)
Date: 2008-02-08 21:49

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I did my tests on Linux only, as I don't have any windows systems around
to test on.

To debug this, I suggest setting a break-point in the function
lib/connect.c:Curl_is_connected() when running Patrick's test case, and
then single-step it to see exactly where it returns error and why there's
no failf() called for that case.

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Comment By: Patrick_ (patrick_)
Date: 2008-02-08 21:32

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I'm using MinGW/GCC 3.4.2 (install Dev-C++ 4.9.9.2 to simulate my
environment); I'm using the -mms-bitfields compiler flag as well. Linking
against curl statically, of course, and my CFLAGS are -Os -s
-fomit-frame-pointer. LFLAGS are -lwinmm -lpsapi -lshfolder -lwsock32
-lshell32.

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Comment By: Yang Tse (yangtse)
Date: 2008-02-08 18:19

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I can reproduce it on W2k with MSVC 6.

On W2k cygwin with gcc 3.4.4 it doesn't fail.

Any direction or additional info or test to debug this ?

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Comment By: Patrick_ (patrick_)
Date: 2008-02-08 18:11

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Hmm, that's odd. Are you linking it statically (have -DCURL_STATICLIB
defined) and running it on Windows XP (I'm using SP1 at the moment)? I can
reproduce this every time. I doubt it will change anything, but try
disconnecting your modem and running the code, as the PC I'm running this
code on is not connected to the 'net at all.

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Comment By: Daniel Stenberg (bagder)
Date: 2008-02-08 12:51

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Sorry, but I can't repeat the problem (using the supplied code) with my
current CVS (not too different than 7.18.0 atm). If I make the destination
port one that isn't used, or if I use a host name that doesn't resolve I
get error messages in both cases.

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Received on 2008-02-09