Extended Description

Emacs 24.3 when compiling on FreeBSD ends up with following segmentation fault:

% gdb temacs
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This GDB was configured as "i386-marcel-freebsd"...
Environment variable "DISPLAY" not defined.
TERM = screen-bce
Breakpoint 1 at 0x80cd031: file emacs.c, line 350.
Breakpoint 2 at 0x80e6d08: file sysdep.c, line 850.
(gdb) core-file temacs.core
Core was generated by `temacs'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /usr/lib/librt.so.1...done.
Loaded symbols for /usr/lib/librt.so.1
Reading symbols from /usr/lib/libexecinfo.so.1...done.
Loaded symbols for /usr/lib/libexecinfo.so.1
Reading symbols from /lib/libutil.so.9...done.
Loaded symbols for /lib/libutil.so.9
Reading symbols from /lib/libncurses.so.8...done.
Loaded symbols for /lib/libncurses.so.8
Reading symbols from /lib/libthr.so.3...done.
Loaded symbols for /lib/libthr.so.3
Reading symbols from /lib/libm.so.5...done.
Loaded symbols for /lib/libm.so.5
Reading symbols from /lib/libz.so.6...done.
Loaded symbols for /lib/libz.so.6
Reading symbols from /lib/libc.so.7...done.
Loaded symbols for /lib/libc.so.7
Reading symbols from /usr/lib/libelf.so.1...done.
Loaded symbols for /usr/lib/libelf.so.1
Reading symbols from /lib/libgcc_s.so.1...done.
Loaded symbols for /lib/libgcc_s.so.1
Reading symbols from /libexec/ld-elf.so.1...done.
Loaded symbols for /libexec/ld-elf.so.1
#​0 format_time_string (format=0x0, formatlen=1, t={tv_sec = 0, tv_nsec = 0}) at editfns.c:1787
1787 buf[0] = '\1';
[New Thread 83ab000 (LWP 100088/temacs)]
Current language: auto; currently minimal
(gdb) bt
#​0 format_time_string (format=0x0, formatlen=1, t={tv_sec = 0, tv_nsec = 0}) at editfns.c:1787
#​1 0x08133df8 in Fformat_time_string (format_string=, timeval=-1619017216) at editfns.c:1756
#​2 0x0813cfe6 in eval_sub (form=) at eval.c:2181
#​3 0x0813ce05 in eval_sub (form=) at eval.c:2139
#​4 0x0813ded1 in Flet (args=) at eval.c:936
#​5 0x0813cd77 in eval_sub (form=) at eval.c:2123
#​6 0x08140aeb in funcall_lambda (fun=, nargs=) at eval.c:458
#​7 0x0813f985 in apply_lambda (fun=138488846, args=) at eval.c:2914
#​8 0x0813cc54 in eval_sub (form=) at eval.c:2220
#​9 0x0813f94e in apply_lambda (fun=138781494, args=) at eval.c:2905
#​10 0x0813cc54 in eval_sub (form=) at eval.c:2220
#​11 0x0813ce05 in eval_sub (form=) at eval.c:2139
#​12 0x0813cea5 in eval_sub (form=) at eval.c:2160
#​13 0x0815b708 in readevalloop (readcharfun=138171994, stream=0x283eb34c, sourcename=, readfun=138064922, start=, end=) at lread.c:1887
#​14 0x0815a77d in Fload (file=, noerror=, nosuffix=, must_suffix=) at lread.c:1358
#​15 0x0813d045 in eval_sub (form=) at eval.c:2189
#​16 0x0815b708 in readevalloop (readcharfun=138171994, stream=0x283eb264, sourcename=, readfun=138064922, start=, end=) at lread.c:1887
#​17 0x0815a77d in Fload (file=, noerror=, nosuffix=, must_suffix=) at lread.c:1358
#​18 0x0813d045 in eval_sub (form=) at eval.c:2189
#​19 0x0813f716 in Feval (form=138093014, lexical=) at eval.c:1993
#​20 0x080df10a in top_level_2 () at keyboard.c:1179
#​21 0x0813eb40 in internal_condition_case (bfun=, handlers=, hfun=) at eval.c:1344

Following is the disassembly of the surrounding area:

0x08133ebe <format_time_string+158>: je 0x8133ed0 <format_time_string+176>
0x08133ec0 <format_time_string+160>: sub $0x4,%esp
0x08133ec3 <format_time_string+163>: lea 0x20(%esi),%eax
0x08133ec6 <format_time_string+166>: mov %eax,(%esp)
0x08133ec9 <format_time_string+169>: call 0x804bdcc gmtime@plt
0x08133ece <format_time_string+174>: jmp 0x8133ede <format_time_string+190>
0x08133ed0 <format_time_string+176>: sub $0x4,%esp
0x08133ed3 <format_time_string+179>: lea 0x20(%esi),%eax
0x08133ed6 <format_time_string+182>: mov %eax,(%esp)
0x08133ed9 <format_time_string+185>: call 0x804b0dc localtime@plt
0x08133ede <format_time_string+190>: add $0x4,%esp
0x08133ee1 <format_time_string+193>: mov %eax,%edx
0x08133ee3 <format_time_string+195>: test %edx,%edx
0x08133ee5 <format_time_string+197>: je 0x8134010 <format_time_string+496>
0x08133eeb <format_time_string+203>: mov $0xb,%ecx
0x08133ef0 <format_time_string+208>: mov 0x14(%ebp),%edi
0x08133ef3 <format_time_string+211>: mov %edx,%esi
0x08133ef5 <format_time_string+213>: rep movsl %ds:(%esi),%es:(%edi)
0x08133ef7 <format_time_string+215>: mov 0x1c(%esi),%ecx
0x08133efa <format_time_string+218>: movb $0x1,(%ecx)
0x08133efd <format_time_string+221>: sub $0x14,%esp
0x08133f00 <format_time_string+224>: mov 0xc(%ebp),%eax

Following is the unoptimized code for the block in question:

.LBB64_6: # in Loop: Header=BB64_1 Depth=1
movl $44, %eax
.loc 1 1785 0 # editfns.c:1785:0
movl 4104(%esi), %ecx
movl 80(%esi), %edx
subl $12, %esp
movl %ecx, (%esp)
movl %edx, 4(%esp)
movl $44, 8(%esp)
movl %eax, 48(%esi) # 4-byte Spill
calll memcpy
addl $12, %esp
.loc 1 1787 0 # editfns.c:1787:0
movl 100(%esi), %eax
movb $1, (%eax)

Following is the -O2 code for the block in question:

    .loc    1 1785 0                # editfns.c:1785:0
    movl    %edx, %esi              ########### %esi gets clobbered here, and never restored after 'rep movsl'
    rep;movsl
    movl    28(%esi), %ecx          # 4-byte Reload
    .loc    1 1787 0                # editfns.c:1787:0
    movb    $1, (%ecx)              ########### Segmentation Fault happens here

Following is the version of "clang":

FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610
Target: i386-unknown-freebsd10.0
Thread model: posix

Let me know if you need more information to debug this.

Thanks