Created attachment 11686 [details] preprocessed editfns.c Emacs 24.3 when compiling on FreeBSD ends up with following segmentation fault: % gdb temacs GNU gdb 6.1.1 [FreeBSD] Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. 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=<value optimized out>, timeval=-1619017216) at editfns.c:1756 #2 0x0813cfe6 in eval_sub (form=<value optimized out>) at eval.c:2181 #3 0x0813ce05 in eval_sub (form=<value optimized out>) at eval.c:2139 #4 0x0813ded1 in Flet (args=<value optimized out>) at eval.c:936 #5 0x0813cd77 in eval_sub (form=<value optimized out>) at eval.c:2123 #6 0x08140aeb in funcall_lambda (fun=<value optimized out>, nargs=<value optimized out>) at eval.c:458 #7 0x0813f985 in apply_lambda (fun=138488846, args=<value optimized out>) at eval.c:2914 #8 0x0813cc54 in eval_sub (form=<value optimized out>) at eval.c:2220 #9 0x0813f94e in apply_lambda (fun=138781494, args=<value optimized out>) at eval.c:2905 #10 0x0813cc54 in eval_sub (form=<value optimized out>) at eval.c:2220 #11 0x0813ce05 in eval_sub (form=<value optimized out>) at eval.c:2139 #12 0x0813cea5 in eval_sub (form=<value optimized out>) at eval.c:2160 #13 0x0815b708 in readevalloop (readcharfun=138171994, stream=0x283eb34c, sourcename=<value optimized out>, readfun=138064922, start=<value optimized out>, end=<value optimized out>) at lread.c:1887 #14 0x0815a77d in Fload (file=<value optimized out>, noerror=<value optimized out>, nosuffix=<value optimized out>, must_suffix=<value optimized out>) at lread.c:1358 #15 0x0813d045 in eval_sub (form=<value optimized out>) at eval.c:2189 #16 0x0815b708 in readevalloop (readcharfun=138171994, stream=0x283eb264, sourcename=<value optimized out>, readfun=138064922, start=<value optimized out>, end=<value optimized out>) at lread.c:1887 #17 0x0815a77d in Fload (file=<value optimized out>, noerror=<value optimized out>, nosuffix=<value optimized out>, must_suffix=<value optimized out>) at lread.c:1358 #18 0x0813d045 in eval_sub (form=<value optimized out>) at eval.c:2189 #19 0x0813f716 in Feval (form=138093014, lexical=<value optimized out>) at eval.c:1993 #20 0x080df10a in top_level_2 () at keyboard.c:1179 #21 0x0813eb40 in internal_condition_case (bfun=<value optimized out>, handlers=<value optimized out>, hfun=<value optimized out>) 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
This is the unholy conjunction of dynamic alloca and stack realignment again. - When we reach the memcpy in @format_time_string the check if %esi is used as a base pointer returns false. We emit a rep;movsl - Then we hit the dynamic alloca in a later BB in the function. We properly set all the flags needed to prevent further allocation of %esi, but it's already too late for the emitted rep;movsl.
*** Bug 18537 has been marked as a duplicate of this bug. ***
I can confirm this is now fixed by r202930 (see bug 19012). I will commit the (slightly modified) revision to FreeBSD 11.0-CURRENT soon.