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bug#28308: Build failure on FreeBSD/aarch64


From: Gergely Czuczy
Subject: bug#28308: Build failure on FreeBSD/aarch64
Date: Mon, 11 Sep 2017 22:33:45 +0200
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

On 2017. 09. 11. 19:17, Eli Zaretskii wrote:
Cc: address@hidden, address@hidden
From: Gergely Czuczy <address@hidden>
Date: Mon, 11 Sep 2017 19:12:12 +0200

That's a call to delete_terminal, which doesn't appear in your
backtrace, and doesn't call xpalloc, either.  So thanks, but I'm still
confused.  Are you sure this is an unoptimized build?  Is it possible
that we are looking at LLDB bug?
It's the lldb debug, right. And I'm sure it's an unoptimized build, I've
went back and checked the build flags:
cc -Demacs  -I. -I. -I../lib -I../lib
-I/usr/local/include/libxml2             -MMD -MF deps/.d -MP
-Wno-switch -Wno-pointer-sign -Wno-string-plus-int
-Wno-unknown-attributes -Wno-initializer-overrides
-Wno-tautological-compare
-Wno-tautological-constant-out-of-range-compare -O0 -g
-fno-strict-aliasing  -Wl,-znocombreloc  (...)

If that helps, I can create a qemu VM with this fbsd build, and give you
the image.
Would it be possible for you to install GDB, and then repeat the same
experiment under GDB?
It was relatively fast, however it appears to be the same:
address@hidden:/usr/ports/editors/emacs-devel/work/emacs-f44184f/lisp# EMACSLOADPATH= lldb -- '../src/bootstrap-emacs' -batch l-no-site-file --no-site-lisp --eval '(setq load-prefer-newer t)' -f batch-byte-compile emacs-lisp/macroexp.elk/emacs-f4
(lldb) target create "../src/bootstrap-emacs"
Current executable set to '../src/bootstrap-emacs' (aarch64).
(lldb) settings set -- target.run-args  "-batch" "--no-site-file" "--no-site-lisp" "--eval" "(setq load-prefer-newer t)" "-f" "batch-byte-compile" "emacs-lisp/macroexp.el"
(lldb) r
Process 98283 launching
Process 98283 launched: '../src/bootstrap-emacs' (aarch64)
Process 98283 stopped
* thread #1, name = 'bootstrap-emacs', stop reason = signal SIGSEGV: invalid address (fault address: 0x41b17978)     frame #0: 0x0000000000228460 bootstrap-emacs`xnrealloc(pa=0x0000000000000000, nitems=0, item_size=1102150015) at alloc.c:939
   936  {
   937    eassert (0 <= nitems && 0 < item_size);
   938    ptrdiff_t nbytes;
-> 939    if (INT_MULTIPLY_WRAPV (nitems, item_size, &nbytes) || SIZE_MAX < nbytes)
   940      memory_full (SIZE_MAX);
   941    return xrealloc (pa, nbytes);
   942  }
(lldb) bt
* thread #1, name = 'bootstrap-emacs', stop reason = signal SIGSEGV: invalid address (fault address: 0x41b17978)   * frame #0: 0x0000000000228460 bootstrap-emacs`xnrealloc(pa=0x0000000000000000, nitems=0, item_size=1102150015) at alloc.c:939     frame #1: 0x0000000000228204 bootstrap-emacs`xnrealloc(pa=0x000000000019ae38, nitems=42949672960, item_size=281474976703896) at alloc.c:939     frame #2: 0x000000000022e208 bootstrap-emacs`xpalloc(pa=0x0000000000000000, nitems=0x0000000041b1797f, nitems_incr_min=1683000, nitems_max=42949672960, item_size=281474976703896) at alloc.c:0     frame #3: 0x0000000000168214 bootstrap-emacs`delete_tty(terminal=0x4f67ed32e8e06446) at term.c:4463
    frame #4: 0x0000000000040190 bootstrap-emacs`__start + 376
    frame #5: 0x0000000040390018 ld-elf.so.1`.rtld_start at rtld_start.S:41
(lldb)

It's still in the delete_ttye function, however, 4463 is a call to delete_terminal, and not to xpalloc. It's interesting why's that frame #2, because lldb also returns the same as we can see in the source:
(lldb) frame select 3
frame #3: 0x0000000000168214 bootstrap-emacs`delete_tty(terminal=0x4f67ed32e8e06446) at term.c:4463
   4460      before delete_terminal.  */
   4461   reset_sys_modes (tty);
   4462
-> 4463   delete_terminal (terminal);
   4464
   4465   xfree (tty->name);
   4466   xfree (tty->type);

However, disassembly gave something interesting:
** 4463   delete_terminal (terminal);
   4464

    0x16820c <+224>: bl     0xd40b4 ; coordinates_in_window + 5312 at window.c:1274
    0x168210 <+228>: bl     0x22e1f8 ; xpalloc + 16084 at alloc.c:992

-> 4465   xfree (tty->name);

->  0x168214 <+232>: bl 0x35b294                  ; text_property_stickiness + 628 at textprop.c:1845
    0x168218 <+236>: ldurb  w8, [x29, #-0x2c]
    0x16821c <+240>: tbz    w8, #0x0, 0x16823c ; <+272> at term.c

The pointer is at the xfree call. However, I the disassembly was too long, I couldn't get anything useful out of it.
And here's the core file: http://czg.harmless.hu/tmp/bootstrap-emacs.core.gz

You can download and analyze it with lldb, it was in the root of the source tree, if that matters. I guess that way you can just open it with lldb yourself, and dig into it.








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