I encountered a segfault in Python's call_readline from LLDB on FreeBSD, with libedit. There is a fix for this issue already in readline.c, but under #ifdef __APPLE__

Backtrace:

(lldb) target create "/data/emaste/src/llvm/build/bin/lldb" --core "lldb-3.7.0.core"
Core file '/tank/emaste/projects/lldb-talk/demo/lldb-3.7.0.core' (x86_64) was loaded.
(lldb) bt
* thread #1: tid = 0, 0x0000000809706dcd readline.so`call_readline(sys_stdin=0x00000008055d9d10, sys_stdout=0x00000008055d9e40, prompt=0x0000000806eb7854) + 397 at readline.c:1132, name = 'lldb-3.7.0', stop reason = signal SIGSEGV
  * frame #0: 0x0000000809706dcd readline.so`call_readline(sys_stdin=0x00000008055d9d10, sys_stdout=0x00000008055d9e40, prompt=0x0000000806eb7854) + 397 at readline.c:1132
    frame #1: 0x0000000805c48f1f libpython2.7.so.1`PyOS_Readline(sys_stdin=0x00000008055d9d10, sys_stdout=0x00000008055d9e40, prompt=0x0000000806eb7854) + 383 at myreadline.c:207
    frame #2: 0x0000000805d7f94f libpython2.7.so.1`builtin_raw_input(self=0x0000000000000000, args=0x000000080bec1df0) + 639 at bltinmodule.c:2060
    frame #3: 0x0000000805cce5c6 libpython2.7.so.1`PyCFunction_Call(func=0x00000008007b78d0, arg=0x000000080bec1df0, kw=0x0000000000000000) + 166 at methodobject.c:81
    frame #4: 0x0000000805d992aa libpython2.7.so.1`call_function(pp_stack=0x00007fffffffbcd0, oparg=1) + 1754 at ceval.c:4033
    frame #5: 0x0000000805d93538 libpython2.7.so.1`PyEval_EvalFrameEx(f=0x0000000806ecfdf0, throwflag=0) + 51160 at ceval.c:2679
    frame #6: 0x0000000805d86c54 libpython2.7.so.1`PyEval_EvalCodeEx(co=0x0000000805a6af60, globals=0x0000000806f9a580, locals=0x0000000000000000, args=0x000000080a06c670, argcount=2, kws=0x000000080a06c680, kwcount=0, defs=0x0000000805aaeda8, defcount=1, closure=0x0000000000000000) + 5284 at ceval.c:3265
    frame #7: 0x0000000805d9c2b6 libpython2.7.so.1`fast_function(func=0x0000000806f7da38, pp_stack=0x00007fffffffc520, n=2, na=2, nk=0) + 822 at ceval.c:4129
    frame #8: 0x0000000805d994c8 libpython2.7.so.1`call_function(pp_stack=0x00007fffffffc520, oparg=1) + 2296 at ceval.c:4054
    frame #9: 0x0000000805d93538 libpython2.7.so.1`PyEval_EvalFrameEx(f=0x000000080a06c4b0, throwflag=0) + 51160 at ceval.c:2679
    frame #10: 0x0000000805d86c54 libpython2.7.so.1`PyEval_EvalCodeEx(co=0x0000000805a5ebf0, globals=0x0000000806f9a580, locals=0x0000000000000000, args=0x000000080a06c3e0, argcount=2, kws=0x000000080a06c3f0, kwcount=0, defs=0x0000000805aaecc8, defcount=1, closure=0x0000000000000000) + 5284 at ceval.c:3265
    frame #11: 0x0000000805d9c2b6 libpython2.7.so.1`fast_function(func=0x0000000806f7d8e8, pp_stack=0x00007fffffffcd70, n=2, na=2, nk=0) + 822 at ceval.c:4129
    frame #12: 0x0000000805d994c8 libpython2.7.so.1`call_function(pp_stack=0x00007fffffffcd70, oparg=1) + 2296 at ceval.c:4054
    frame #13: 0x0000000805d93538 libpython2.7.so.1`PyEval_EvalFrameEx(f=0x000000080a06c230, throwflag=0) + 51160 at ceval.c:2679
    frame #14: 0x0000000805d86c54 libpython2.7.so.1`PyEval_EvalCodeEx(co=0x0000000805a869e0, globals=0x0000000806f9a580, locals=0x0000000000000000, args=0x000000080a06b9f8, argcount=0, kws=0x000000080a06b9f8, kwcount=2, defs=0x00000008009af688, defcount=3, closure=0x0000000000000000) + 5284 at ceval.c:3265
    frame #15: 0x0000000805d9c2b6 libpython2.7.so.1`fast_function(func=0x0000000806f7d300, pp_stack=0x00007fffffffd5c0, n=4, na=0, nk=2) + 822 at ceval.c:4129
    frame #16: 0x0000000805d994c8 libpython2.7.so.1`call_function(pp_stack=0x00007fffffffd5c0, oparg=512) + 2296 at ceval.c:4054
    frame #17: 0x0000000805d93538 libpython2.7.so.1`PyEval_EvalFrameEx(f=0x000000080a06b830, throwflag=0) + 51160 at ceval.c:2679
    frame #18: 0x0000000805d9c16a libpython2.7.so.1`fast_function(func=0x0000000806f9d300, pp_stack=0x00007fffffffdbd0, n=1, na=1, nk=0) + 490 at ceval.c:4119
    frame #19: 0x0000000805d994c8 libpython2.7.so.1`call_function(pp_stack=0x00007fffffffdbd0, oparg=1) + 2296 at ceval.c:4054
    frame #20: 0x0000000805d93538 libpython2.7.so.1`PyEval_EvalFrameEx(f=0x000000080098c9c0, throwflag=0) + 51160 at ceval.c:2679
    frame #21: 0x0000000805d86c54 libpython2.7.so.1`PyEval_EvalCodeEx(co=0x00000008008ffa90, globals=0x00000008007d8580, locals=0x00000008007d8580, args=0x0000000000000000, argcount=0, kws=0x0000000000000000, kwcount=0, defs=0x0000000000000000, defcount=0, closure=0x0000000000000000) + 5284 at ceval.c:3265
    frame #22: 0x0000000805d857a5 libpython2.7.so.1`PyEval_EvalCode(co=0x00000008008ffa90, globals=0x00000008007d8580, locals=0x00000008007d8580) + 85 at ceval.c:667
    frame #23: 0x0000000805dd4a15 libpython2.7.so.1`run_mod(mod=0x000000080a14f128, filename=0x0000000805e22022, globals=0x00000008007d8580, locals=0x00000008007d8580, flags=0x0000000000000000, arena=0x000000080a027800) + 101 at pythonrun.c:1371
    frame #24: 0x0000000805dd50a4 libpython2.7.so.1`PyRun_StringFlags(str=0x000000080a0ff820, start=257, globals=0x00000008007d8580, locals=0x00000008007d8580, flags=0x0000000000000000) + 148 at pythonrun.c:1334
    frame #25: 0x0000000805dd4f54 libpython2.7.so.1`PyRun_SimpleStringFlags(command=0x000000080a0ff820, flags=0x0000000000000000) + 100 at pythonrun.c:975
    frame #26: 0x0000000802085fa4 liblldb.so.3.7`IOHandlerPythonInterpreter::Run() + 324
    frame #27: 0x0000000801f78c12 liblldb.so.3.7`lldb_private::Debugger::ExecuteIOHandlers() + 162
    frame #28: 0x000000080206635e liblldb.so.3.7`lldb_private::CommandInterpreter::RunCommandInterpreter(bool, bool, lldb_private::CommandInterpreterRunOptions&) + 126
    frame #29: 0x00000008012bc79f liblldb.so.3.7`lldb::SBDebugger::RunCommandInterpreter(bool, bool) + 63
    frame #30: 0x0000000000406546 lldb`Driver::MainLoop() + 2454
    frame #31: 0x0000000000406a17 lldb`main + 439
    frame #32: 0x000000000040362f lldb`_start + 367

frame #0: 0x0000000809706dcd readline.so`call_readline(sys_stdin=0x00000008055d9d10, sys_stdout=0x00000008055d9e40, prompt=0x0000000806eb7854) + 397 at readline.c:1132
   1129                 line = history_get(length + libedit_history_start - 1)->line;
   1130             } else
   1131 #endif /* __APPLE__ */
-> 1132             line = history_get(length)->line;
   1133         else
   1134             line = "";
   1135         if (strcmp(p, line))

It looks like a straightforward s/#ifdef __APPLE__/#if defined(__APPLE__) || defined(__FreeBSD__)/ fixes the issue (as in the attached proof of concept patch).

Presumably the #ifdefs ought to just be deleted though, relying on the runtime detection of libedit compatibility issues on any platform.

See also Issue 13501 for a more platform-independent approach.

I think this crash is actually due to a bug in Editline (later fixed; see Issue 18458), but since Python already has the workaround, it makes sense to use the workaround if necessary for Free BSD, or maybe even in general.

The change in spec in editline was to better match GNU readline behavior.  Unfortunately, we depended on the old behavior.  Technically, we don't support editline out-of-the-box other than on OS X; as Martin notes, generalizing that support is what Issue13501 is about.  I'm going to close this as a duplicate of it.