transmission-gtk crashes with segfault on start on arm-uclibcgnueabi system

[alllexx]

I'm trying to get transmission 2.84 GTK+ client to work on an uClibc ARM system using Optware. transmission-daemon works fine, however starting transmission-gtk results in a Segmentation fault. See gdb log attached. This may be some sort of a build problem, since I have only recently ported GTK+ to Optware, but I have at least confirmed that GTK+ is working (vte-0.36.3 runs fine). GTK+ is 3.14.9

[alllexx]

transmission-gtk crash gdb log

[mike.dld]

Is there an error which looks like Couldn't read "/root/.config/transmission/stats.json": ... in the log right when the crash occurs? What does it say exactly after the colon?

Do you have the aforementioned stats.json file at that path? Is it a regular file, are you able to read its content?

---

P.S. Since GTK+ client queues messages instead of writing them out right away, you can patch on_startup function to get them dumped to stderr:

gtk/main.c

@@ -523 +523 @@
     g_mkdir_with_parents (str, 0777);
 
   /* initialize the libtransmission session */
-  session = tr_sessionInit ("gtk", cbdata->config_dir, TRUE, gtr_pref_get_all ());
+  session = tr_sessionInit ("gtk", cbdata->config_dir, FALSE, gtr_pref_get_all ());
 
   gtr_pref_flag_set (TR_KEY_alt_speed_enabled, tr_sessionUsesAltSpeed (session));
   gtr_pref_int_set  (TR_KEY_peer_port, tr_sessionGetPeerPort (session));

[mike.dld]

Also, could you try building lastest trunk revision (checkout from ​svn://svn.transmissionbt.com/Transmission/trunk) to see if that helps?

[alllexx]

Replying to mike.dld:

Is there an error which looks like Couldn't read "/root/.config/transmission/stats.json": ... in the log right when the crash occurs? What does it say exactly after the colon?

Do you have the aforementioned stats.json file at that path? Is it a regular file, are you able to read its content?

---

P.S. Since GTK+ client queues messages instead of writing them out right away, you can patch on_startup function to get them dumped to stderr:

gtk/main.c

@@ -523 +523 @@
     g_mkdir_with_parents (str, 0777);
 
   /* initialize the libtransmission session */
-  session = tr_sessionInit ("gtk", cbdata->config_dir, TRUE, gtr_pref_get_all ());
+  session = tr_sessionInit ("gtk", cbdata->config_dir, FALSE, gtr_pref_get_all ());
 
   gtr_pref_flag_set (TR_KEY_alt_speed_enabled, tr_sessionUsesAltSpeed (session));
   gtr_pref_int_set  (TR_KEY_peer_port, tr_sessionGetPeerPort (session));

No, there is no /root/.config/transmission/stats.json. Sorry for this stupid questions, but where exactly should I look for the logs? Can't seem to find it in any standard locations. I build from trunk (rev14475), but still get a segfault (see transmission-gtk-bt2). Applying your patch does not seem to give any useful hints:

[root@unknown root]$ transmission-gtk

** (transmission-gtk:15228): WARNING **: Couldn't connect to accessibility bus: Failed to connect to socket /tmp/dbus-U15izXXyus: Connection refused
[2015-03-14 20:29:22.166] Transmission 2.84+ (14475) started
[2015-03-14 20:29:22.168] RPC Server: Adding address to whitelist: 127.0.0.1
[2015-03-14 20:29:22.241] UDP: Failed to set receive buffer: requested 4194304, got 241664
[2015-03-14 20:29:22.241] UDP: Please add the line "net.core.rmem_max = 4194304" to /etc/sysctl.conf
[2015-03-14 20:29:22.241] UDP: Failed to set send buffer: requested 1048576, got 241664
[2015-03-14 20:29:22.241] UDP: Please add the line "net.core.wmem_max = 1048576" to /etc/sysctl.conf
Segmentation fault

[alllexx]

P.S. If you mean gdb logs, no there is no Couldn't read "/root/.config/transmission/stats.json" error there

[mike.dld]

Could you please apply one more patch to increase log verbosity and try again?

libtransmission/log.c

@@ -19 +19 @@
 #include "platform.h" /* tr_lock */
 #include "utils.h"
 
-tr_log_level __tr_message_level  = TR_LOG_ERROR;
+tr_log_level __tr_message_level  = TR_LOG_DEBUG;
 
 static bool           myQueueEnabled = false;
 static tr_log_message *  myQueue = NULL;

This will hopefully reveal the Couldn't read ... message. And no, it wasn't about GDB logs, but those appeared on strerr when you run transmission-gtk (Transmission 2.84+ (14475) started etc.)

From what I see right now the only way this could happen it seems is if stat(2) call reports an error (file not found) but doesn't set errno appropriately. The code which does error checking is actually flawed and I'll fix it as soon as I hear back from you. It's just really interesting how this could've happened in the first place (bug in uClibc?..)

[alllexx]

Patch applied:

[root@unknown root]$ transmission-gtk

** (transmission-gtk:15456): WARNING **: Couldn't connect to accessibility bus: Failed to connect to socket /tmp/dbus-U15izXXyus: Connection refused
[2015-03-14 22:02:19.090] Couldn't read "/root/.config/user-dirs.dirs": No such file or directory
[2015-03-14 22:02:19.091] Couldn't read "/root/.config/transmission/settings.json": No such file or directory
[2015-03-14 22:02:19.194] Transmission 2.84+ (14475) started
[2015-03-14 22:02:19.196] RPC Server: Adding address to whitelist: 127.0.0.1
[2015-03-14 22:02:19.273] UDP: Failed to set receive buffer: requested 4194304, got 241664
[2015-03-14 22:02:19.273] UDP: Please add the line "net.core.rmem_max = 4194304" to /etc/sysctl.conf
[2015-03-14 22:02:19.273] UDP: Failed to set send buffer: requested 1048576, got 241664
[2015-03-14 22:02:19.273] UDP: Please add the line "net.core.wmem_max = 1048576" to /etc/sysctl.conf
Segmentation fault

Hope this helps

[mike.dld]

Not what I expected, but still interesting. Could it be that you are using some old uClibc version, specifically 0.9.31 and below? I see they have a bug registered at ​https://bugs.uclibc.org/2089, which I found looking at ​http://lists.busybox.net/pipermail/uclibc/2010-July/044196.html (describing stat call specifically). There's also a bunch of other related results if you google for "uclibc" "errno" thread. I know those pages date back to 2010, but since the bug was closed as WONTFIX maybe it's still actual and one of patches will work for you.

[alllexx]

I'm using the latest 0.9.33.2 uClibc, but still you were 100% right/ After partially applying this patch ​https://github.com/mat-c/uClibc/commit/328d392c54aa5dc2b8e7f398a419087de497de2b (file libc/sysdeps/linux/common/bits/uClibc_errno.h does not exist in uClibc 0.9.33.2 and __uClibc_main.c is missing the relevent portion), transmission-gtk starts perfectly fine. Here's the patch I used:

include/netdb.h

@@ -59 +59 @@
 
 /* Function to get address of global `h_errno' variable.  */
 extern int *__h_errno_location (void) __THROW __attribute__ ((__const__));
-libc_hidden_proto(__h_errno_location)
+//libc_hidden_proto(__h_errno_location)
 
 /* Macros for accessing h_errno from inside libc.  */
 #ifdef _LIBC

libc/misc/internals/__errno_location.c

@@ -12 +12 @@
     return &errno;
 }
 #ifdef IS_IN_libc /* not really need, only to keep in sync w/ libc_hidden_proto */
-libc_hidden_weak(__errno_location)
+//libc_hidden_weak(__errno_location)
 #endif

libc/misc/internals/__h_errno_location.c

@@ -10 +10 @@
 {
     return &h_errno;
 }
-libc_hidden_weak(__h_errno_location)
+//libc_hidden_weak(__h_errno_location)

libc/sysdeps/linux/common/bits/errno.h

@@ -43 +43 @@
 # ifndef __ASSEMBLER__
 /* Function to get address of global `errno' variable.  */
 extern int *__errno_location (void) __THROW __attribute__ ((__const__));
-libc_hidden_proto(__errno_location)
+//libc_hidden_proto(__errno_location)
 
 #  ifdef __UCLIBC_HAS_THREADS__
 /* When using threads, errno is a per-thread value.  */

So it is a uClibc bug after all. Thanks!

P.S. Now I have to figure out how to make transmission-gtk search for gschemas.compiled in /opt/share/glib-2.0/schemas/ rather than /usr/share/glib-2.0/schemas/. transmission-gtk crashes when I press File->Open. Not sure what needs to be patched, though: transmission or glib...

[mike.dld]

Committed the fix I had in mind (comment:5) as r14491.