Crash when error is produced inside try/catch block on CmdlineEnter or CmdlineLeave

[markonm]

• nvim --version: NVIM v0.2.3-dev
• Vim (version: ) behaves differently? Yes
• Operating system/version: Windows 10, WSL

Steps to reproduce using nvim -u NORC

" reproduce.vim
function! s:crash() abort
  try
    gibberish
  catch
    " nop
  endtry
endfunction
autocmd CmdlineEnter,CmdlineLeave : call s:crash()

nvim -u NORC
:so reproduce.vim
:

Actual behaviour

Crash.

nvim: /build/neovim-MwR3Wh/neovim-0.2.0ubuntu1+git201712200021+3828+26~ubuntu16.04.1/src/nvim/api/private/helpers.c:88: try_leave: Assertion `current_exception == NULL' failed.
~                                                       Aborted (core dumped)

Expected behaviour

No crash.

[jamessan]

@ZyX-I This is failing in the assert added by 2a6423e.

#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007f15c84d5cf7 in __GI_abort () at abort.c:90
#2  0x00007f15c84ccfca in __assert_fail_base (fmt=0x7f15c861d890 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", 
    assertion=assertion@entry=0x1bddd20 <.str.7> "current_exception == NULL", file=file@entry=0x1be6398 "../src/nvim/api/private/helpers.c", 
    line=line@entry=88, function=function@entry=0x1bddae0 <__PRETTY_FUNCTION__.try_leave> "_Bool try_leave(const TryState *const, Error *const)")
    at assert.c:92
#3  0x00007f15c84cd042 in __GI___assert_fail (assertion=0x1bddd20 <.str.7> "current_exception == NULL", 
    file=0x1be6398 "../src/nvim/api/private/helpers.c", line=88, 
    function=0x1bddae0 <__PRETTY_FUNCTION__.try_leave> "_Bool try_leave(const TryState *const, Error *const)") at assert.c:101
#4  0x00000000005eb9ae in try_leave (tstate=0x7ffd74e76940, err=0x7ffd74e76990) at ../src/nvim/api/private/helpers.c:88
#5  0x0000000000c5d19c in command_line_enter (firstc=58, count=1, indent=0) at ../src/nvim/ex_getln.c:374
#6  0x0000000000c55d31 in getcmdline (firstc=58, count=1, indent=0) at ../src/nvim/ex_getln.c:1920
#7  0x0000000000c61c56 in getexline (c=58, cookie=0x0, indent=0) at ../src/nvim/ex_getln.c:2100
#8  0x0000000000b7fc21 in do_cmdline (cmdline=0x0, fgetline=0xc61bc0 <getexline>, cookie=0x0, flags=0) at ../src/nvim/ex_docmd.c:528
#9  0x000000000115fa3c in nv_colon (cap=0x7ffd74e79940) at ../src/nvim/normal.c:4552
#10 0x0000000001146a01 in normal_execute (state=0x7ffd74e798a0, key=58) at ../src/nvim/normal.c:1136
#11 0x00000000017d7361 in state_enter (s=0x7ffd74e798a0) at ../src/nvim/state.c:67
#12 0x00000000010fd520 in normal_enter (cmdwin=false, noexmode=false) at ../src/nvim/normal.c:466
#13 0x0000000000edc8da in main (argc=3, argv=0x7ffd74e7a158) at ../src/nvim/main.c:572

[bfredl]

I can get the same crash with g:Nvim_color_cmdline using

function! Crash2(cmdline) abort
  try
    gibberish
  catch
    " nop
  endtry
  return []
endfunction
let g:Nvim_color_cmdline = "Crash2"

Otherwise try_leave is not used.

[ZyX-I]

The documentation for current_exception states that it is valid only when did_throw is true which is not the case. I am currently not sure whether I could simply remove that assert(): just doing this has good potential for introducing memory leak.

[ZyX-I]

Ready test for the problem:

diff --git a/test/functional/ui/cmdline_highlight_spec.lua b/test/functional/ui/cmdline_highlight_spec.lua
index ffb6a26ae..f9cec903a 100644
--- a/test/functional/ui/cmdline_highlight_spec.lua
+++ b/test/functional/ui/cmdline_highlight_spec.lua
@@ -737,6 +737,22 @@ describe('Command-line coloring', function()
     feed('<CR><CR>')
     eq('', meths.get_var('out'))
   end)
+  it('does not crash when callback has caught not-a-editor-command exception',
+  function()
+    source([[
+      function CaughtExc(cmdline) abort
+        try
+          gibberish
+        catch
+          " Do nothing
+        endtry
+        return []
+      endfunction
+    ]])
+    set_color_cb('CaughtExc')
+    start_prompt('1')
+    eq(1, meths.eval('1'))
+  end)
 end)
 describe('Ex commands coloring support', function()
   it('works', function()

, crashes with

[----------] Global test environment setup.
[----------] Running tests from test/functional/ui/cmdline_highlight_spec.lua
[ RUN      ] Command-line coloring does not crash when callback has caught not-a-editor-command exception: nvim: /home/zyx/a.a/Proj/c/neovim/src/nvim/api/private/helpers.c:88: _Bool try_leave(const TryState *const, Error *const): Assertion `current_exception == NULL' failed.
FAIL
test/functional/ui/cmdline_highlight_spec.lua:754: Expected objects to be the same.
Passed in:
(nil)
Expected:
(number) 1

stack traceback:
        test/functional/ui/cmdline_highlight_spec.lua:754: in function <test/functional/ui/cmdline_highlight_spec.lua:741>

[----------] 1 test from test/functional/ui/cmdline_highlight_spec.lua (529.92 ms total)

[----------] Global test environment teardown.
[==========] 1 test from 1 test file ran. (530.29 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] test/functional/ui/cmdline_highlight_spec.lua @ 740: Command-line coloring does not crash when callback has caught not-a-editor-command exception
test/functional/ui/cmdline_highlight_spec.lua:754: Expected objects to be the same.
Passed in:
(nil)
Expected:
(number) 1

stack traceback:
        test/functional/ui/cmdline_highlight_spec.lua:754: in function <test/functional/ui/cmdline_highlight_spec.lua:741>


 1 FAILED TEST