From: Mike Pall <mike>

Reported by Alex Orlenko.

(cherry picked from commit b4b2dce9fc3ffaaaede39b36d06415311e2aa516)

The `pcall()` assembler preambule modifies `RC` (`x28`) (N args * 8)

The «`RC` (`x28`) (N args * 8)» expression is hard to percieve. I suggest

reformulating it in a way like «modifies `RC`, which is mapped to `x28`, so

it has value ...». Feel free to ignore.

during the check of the amount of the given arguments. So, this wrong
value using in the `fff_fallback` routine leading to a crash on the

Typo: s/using/being used/

Typo: s/leading/leads

Typo: s/on the/on

error throwing, because the Lua stack is filled incorrect and can't be

Typo: s/is filled incorrect/is incorrectly filled/

unwound.

This patch adds the additional comparison before taking the fallback
branch and modifies `RC` only after this branch.

Sergey Kaplun:
* added the description and the test for the problem

Part of tarantool/tarantool#8069
---

PR: https://github.com/tarantool/tarantool/pull/8295
Branch: https://github.com/tarantool/luajit/tree/skaplun/lj-762-arm64-pcall-no-arg
Issues:
* https://github.com/tarantool/tarantool/issues/8069
* https://github.com/LuaJIT/LuaJIT/issues/762

 src/vm_arm64.dasc | 3 ++-
 test/tarantool-tests/lj-762-pcall-no-arg.test.lua | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 test/tarantool-tests/lj-762-pcall-no-arg.test.lua

diff --git a/src/vm_arm64.dasc b/src/vm_arm64.dasc
index f517a808..e8b63d33 100644
--- a/src/vm_arm64.dasc
+++ b/src/vm_arm64.dasc
@@ -1168,9 +1168,10 @@ static void build_subroutines(BuildCtx *ctx)
   |//-- Base library: catch errors ----------------------------------------
   |
   |.ffunc pcall
+ | cmp NARGS8:RC, #8
   | ldrb TMP0w, GL->hookmask
- | subs NARGS8:RC, NARGS8:RC, #8
   | blo ->fff_fallback
+ | sub NARGS8:RC, NARGS8:RC, #8
   | mov RB, BASE
   | add BASE, BASE, #16
   | ubfx TMP0w, TMP0w, #HOOK_ACTIVE_SHIFT, #1
diff --git a/test/tarantool-tests/lj-762-pcall-no-arg.test.lua b/test/tarantool-tests/lj-762-pcall-no-arg.test.lua
new file mode 100644
index 00000000..6cbfe707
--- /dev/null
+++ b/test/tarantool-tests/lj-762-pcall-no-arg.test.lua
@@ -0,0 +1,15 @@
+local tap = require('tap')
+
+-- Test file to check error raising for `pcall()` without
+-- arguments. Regardless that the problem is aarch64-specific,
+-- it is good to test it for all arches.
+-- See also https://github.com/LuaJIT/LuaJIT/issues/762.
+local test = tap.test('lj-762-pcall-no-arg')
+test:plan(2)
+
+local result, err = pcall(pcall)
+
+test:ok(not result, 'pcall() without args: bad status')
+test:like(err, 'value expected', 'pcall() without args: error message')
+
+os.exit(test:check() and 0 or 1)
--
2.34.1

--
Best regards,

Maxim Kokryashkin