catgirl@gentoo ~> gdb --args mbsync -V -D uf GNU gdb (Gentoo 17.2 vanilla) 17.2 Copyright (C) 2025 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "aarch64-unknown-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <https://bugs.gentoo.org/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>.
For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from mbsync... Reading symbols from /usr/lib/debug/usr/bin/mbsync.debug... (gdb) run Starting program: /usr/bin/mbsync -V -D uf [Thread debugging using libthread_db enabled] Using host libthread_db library "/usr/lib64/libthread_db.so.1". isync 1.5.1 called with: '-V' '-D' 'uf' Reading configuration file /home/catgirl/.config/isyncrc merge ops (in Channel 'uf'): common: OP_EXPUNGE,OP_CREATE far: XOP_HAVE_EXPUNGE,XOP_HAVE_CREATE near: => far: OP_EXPUNGE,OP_CREATE,XOP_HAVE_EXPUNGE,XOP_HAVE_CREATE => near: OP_EXPUNGE,OP_CREATE merge ops (in global config section): common: OP_EXPUNGE,OP_CREATE far: XOP_HAVE_EXPUNGE,XOP_HAVE_CREATE near: => far: OP_EXPUNGE,OP_CREATE,XOP_HAVE_EXPUNGE,XOP_HAVE_CREATE => near: OP_EXPUNGE,OP_CREATE channel ops (uf): far: near: Channel uf Opening far side store uf-remote... F: [ 1] Enter connect_store Resolving outlook.office365.com... [Detaching after fork from child process 148130] F: [ 1] Leave connect_store Opening near side store uf-local... N: [ 2] Enter connect_store N: [ 2] Callback enter connect_store, sts=0 pattern '*' (effective '*'): Path, no INBOX N: [ 3] Enter list_store, flags=2 N: [ 3] Callback enter list_store, sts=0 N: [ 3] Callback leave list_store N: [ 3] Leave list_store N: [ 2] Callback leave connect_store N: [ 2] Leave connect_store Connecting to outlook.office365.com (52.96.165.178:993)... Connection is now encrypted F: * OK Microsoft Exchange IMAP4 service ready. (redacted) (tcpproxy/15.21.0339.010 BACKENDAUTHENTICATE) [(redacted)] F: >>> 1 CAPABILITY F: * CAPABILITY IMAP4 IMAP4rev1 AUTH=PLAIN AUTH=XOAUTH2 SASL-IR UIDPLUS MOVE ID UNSELECT CHILDREN IDLE NAMESPACE LITERAL+ F: 1 OK CAPABILITY completed. Logging in... [Detaching after vfork from child process 148131] Fatal: buffer too small. Please report a bug. Program received signal SIGABRT, Aborted. 0x0000fffff7858644 in ?? () from /usr/lib64/libc.so.6 (gdb) bt #0 0x0000fffff7858644 in ?? () from /usr/lib64/libc.so.6 #1 0x0000fffff7807018 in raise () from /usr/lib64/libc.so.6 #2 0x0000fffff77f25d0 in abort () from /usr/lib64/libc.so.6 #3 0x0000aaaaaaaa570c in oob () at util.c:612 #4 0x0000aaaaaaaa5eac in xvprintf_core (fmt=<optimized out>, ap=..., cb=cb@entry=0xaaaaaaaa63a0 <xasprintf_cb>, cb_aux=cb_aux@entry=0xffffffffef40) at util.c:232 #5 0x0000aaaaaaaa61a8 in xvasprintf (fmt=<optimized out>, ap=<error reading variable: Cannot access memory at address 0x2429c>) at util.c:347 #6 0x0000aaaaaaab2ee8 in imap_exec (ctx=0xaaaaaaaf5af0, cmdp=0xaaaaaacadbb0, done=<optimized out>, fmt=<optimized out>) at drv_imap.c:539 #7 0x0000aaaaaaaaf0cc in done_imap_cmd (ctx=0xaaaaaaaf5af0, cmd=0xaaaaaacadc80, response=<optimized out>) at drv_imap.c:359 #8 0x0000aaaaaaab46e8 in imap_socket_read (aux=0xaaaaaaaf5af0) at drv_imap.c:1931 #9 0x0000aaaaaaaa72b8 in event_wait () at util.c:1129 #10 main_loop () at util.c:1203 #11 0x0000aaaaaaac46a4 in sync_chans (cvars=cvars@entry=0xfffffffff318, argv=<optimized out>) at main_sync.c:368 #12 0x0000aaaaaaaa4378 in main (argc=4, argv=0xfffffffff5b8) at main.c:582 The abort is in xvprintf_core (util.c:232) reaching oob() at util.c:612, called via xvasprintf from imap_exec (drv_imap.c:539). So it's a limit in the printf implementation rather than a buffer in the auth path, which may be why it wasn't where you looked. Note this is the xasprintf_cb path, so it's presumably not specific to credentials -- any sufficiently long formatted string should hit it. Aug 19, 2026, 06:34 by [email protected]: > On Wed, Aug 19, 2026 at 01:04:28AM +0200, sourcefrg3--- via isync-devel wrote: > >> mbsync 1.5.1 aborts with SIGABRT while logging in to outlook.office365.com. >> > whoops. > >> Happy to provide a backtrace >> > yeah, that would help. i'm obviously just being blind, but i failed to locate > the relevant fixed-size buffer. :-} > > > > _______________________________________________ > isync-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/isync-devel >
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