[Tarantool-patches] [PATCH luajit 3/3] core: remove excess assertion inside memprof

[Sergey Kaplun <skaplun@tarantool.org>]

lj_debug_frameline() may return -1 for Lua functions on top.
In this case assertion inside memprof_write_lfunc() that returned line
is not negative is incorrect.

This patch removes this assertion. For negative returned line value
profiler is reported zero frameline.

Follows up tarantool/tarantool#5442
---

I have not thought of any more correct check than:
| -- Check alocations for Lua function on top.
| -- This is not the best test case but the most simple.
| -- Trace allocation on top leads to assertion.
| jit.on()
| for _ = 1, 100 do
|   local _ = tostring(_)
| end
| jit.off()
| jit.flush()

But this is not very fair: here we have tail call to cpcall()
(with trace_state() as an argument) without creating a new guest stack
frame. Also test looks redundant -- assertion obviously can't fail as
far as it doesn't exist. But I can add this test case if you want.

 src/lj_memprof.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/lj_memprof.c b/src/lj_memprof.c
index c4d2645..0568049 100644
--- a/src/lj_memprof.c
+++ b/src/lj_memprof.c
@@ -90,15 +90,15 @@ static void memprof_write_lfunc(struct lj_wbuf *out, uint8_t aevent,
 				cTValue *nextframe)
 {
   const BCLine line = lj_debug_frameline(L, fn, nextframe);
+  lj_wbuf_addbyte(out, aevent | ASOURCE_LFUNC);
+  lj_wbuf_addu64(out, (uintptr_t)funcproto(fn));
   /*
-  ** Line is always >= 0 if we are inside a Lua function.
+  ** Line is >= 0 if we are inside a Lua function.
+  ** An exception may be when the Lua function is on top.
   ** Equals to zero when LuaJIT is built with the
   ** -DLUAJIT_DISABLE_DEBUGINFO flag.
   */
-  lua_assert(line >= 0);
-  lj_wbuf_addbyte(out, aevent | ASOURCE_LFUNC);
-  lj_wbuf_addu64(out, (uintptr_t)funcproto(fn));
-  lj_wbuf_addu64(out, (uint64_t)line);
+  lj_wbuf_addu64(out, line >= 0 ? (uint64_t)line : 0);
 }
 
 static void memprof_write_cfunc(struct lj_wbuf *out, uint8_t aevent,
-- 
2.28.0