[Tarantool-patches] [PATCH luajit v2 1/3] Improve error reporting on stack overflow.

[Maksim Kokryashkin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

From: Mike Pall <mike>

Thanks to Nicolas Lebedenco.

(cherry-picked from commit 8135de2a0204e6acd92b231131c4a1e0be03ac1c)

The `lj_state_growstack` doesn't account for a potential error
handler invocation by xpcall, which may lead to the second error
while handling a stack overflow, resulting in a misleading error
"error in error handling", while the real issue is a stack
overflow. This patch addresses this issue by fixing the condition
at which stack overflow errors are thrown. Now it's thrown if the
stack size is at least at the limit, instead of when it is over
the limit.

This commit also disables the second test from
`lj-603-err-snap-restore`, since after this patch and the two
follow-ups for it, there is no such amount of stack slots with
which the test works the way it should.

Lastly, this patch adds an alternative to `luacmd` to the
`utils.exec` module, which is called `luabin`. That function is
similar to the `luacmd`, with the only difference of returning
only the executable itself without any additional CLI options
passed.

Maxim Kokryashkin:
* added the description and the test for the problem

Part of tarantool/tarantool#9145
---
 src/lj_state.c                                    |  2 +-
 .../lj-603-err-snap-restore.test.lua              |  1 +
 .../lj-962-stack-overflow-report.test.lua         |  9 +++++++++
 .../lj-962-stack-overflow-report/script.lua       |  2 ++
 test/tarantool-tests/utils/exec.lua               | 15 ++++++++++++---
 5 files changed, 25 insertions(+), 4 deletions(-)
 create mode 100644 test/tarantool-tests/lj-962-stack-overflow-report.test.lua
 create mode 100644 test/tarantool-tests/lj-962-stack-overflow-report/script.lua

diff --git a/src/lj_state.c b/src/lj_state.c
index 684336d5..76153bad 100644
--- a/src/lj_state.c
+++ b/src/lj_state.c
@@ -132,7 +132,7 @@ void LJ_FASTCALL lj_state_growstack(lua_State *L, MSize need)
       n = LJ_STACK_MAX;
   }
   resizestack(L, n);
-  if (L->stacksize > LJ_STACK_MAXEX)
+  if (L->stacksize >= LJ_STACK_MAXEX)
     lj_err_msg(L, LJ_ERR_STKOV);
 }
 
diff --git a/test/tarantool-tests/lj-603-err-snap-restore.test.lua b/test/tarantool-tests/lj-603-err-snap-restore.test.lua
index 96ebf92c..f5c8474f 100644
--- a/test/tarantool-tests/lj-603-err-snap-restore.test.lua
+++ b/test/tarantool-tests/lj-603-err-snap-restore.test.lua
@@ -36,6 +36,7 @@ local function do_test()
     -- Tarantool at start, so just skip test for it.
     -- luacheck: no global
     ['Disable test for Tarantool'] = _TARANTOOL,
+    ['Stack overflow is now handled differently'] = true,
   })
 
   test:ok(not handler_is_called)
diff --git a/test/tarantool-tests/lj-962-stack-overflow-report.test.lua b/test/tarantool-tests/lj-962-stack-overflow-report.test.lua
new file mode 100644
index 00000000..26a90f8d
--- /dev/null
+++ b/test/tarantool-tests/lj-962-stack-overflow-report.test.lua
@@ -0,0 +1,9 @@
+local tap = require('tap')
+local test = tap.test('lj-962-stack-overflow-report')
+test:plan(1)
+
+local LUABIN = require('utils').exec.luabin(arg)
+local SCRIPT = arg[0]:gsub('%.test%.lua$', '/script.lua')
+local output = io.popen(LUABIN .. ' 2>&1 ' .. SCRIPT, 'r'):read('*all')
+test:like(output, 'stack overflow', 'stack overflow reported correctly')
+test:done(true)
diff --git a/test/tarantool-tests/lj-962-stack-overflow-report/script.lua b/test/tarantool-tests/lj-962-stack-overflow-report/script.lua
new file mode 100644
index 00000000..52734f2c
--- /dev/null
+++ b/test/tarantool-tests/lj-962-stack-overflow-report/script.lua
@@ -0,0 +1,2 @@
+-- luacheck: no global
+f = function() f() end; f()
diff --git a/test/tarantool-tests/utils/exec.lua b/test/tarantool-tests/utils/exec.lua
index a56ca2dc..7ed0a9d8 100644
--- a/test/tarantool-tests/utils/exec.lua
+++ b/test/tarantool-tests/utils/exec.lua
@@ -1,14 +1,23 @@
 local M = {}
 
-function M.luacmd(args)
+local function cmd_start_idx(args)
   -- arg[-1] is guaranteed to be not nil.
   local idx = -2
   while args[idx] do
     assert(type(args[idx]) == 'string', 'Command part have to be a string')
     idx = idx - 1
   end
-  -- return the full command with flags.
-  return table.concat(args, ' ', idx + 1, -1)
+  return idx + 1
+end
+
+function M.luabin(args)
+  -- Return only the executable.
+  return args[cmd_start_idx(args)]
+end
+
+function M.luacmd(args)
+  -- Return the full command with flags.
+  return table.concat(args, ' ', cmd_start_idx(args), -1)
 end
 
 local function makeenv(tabenv)
-- 
2.39.3 (Apple Git-145)