[tarantool-patches] [PATCH 3/3] Show names of Lua functions in backtraces

[Georgy Kirichenko <georgy@tarantool.org>]

Trace corresponding Lua state as well as normal C stack frames while
fiber backtracing. This might be useful for debugging purposes.

Fixes: #3538
---
 src/lua/fiber.c         | 86 +++++++++++++++++++++++++++++++++++------
 test/app/fiber.result   | 33 ++++++++++++++++
 test/app/fiber.test.lua | 12 ++++++
 3 files changed, 120 insertions(+), 11 deletions(-)

diff --git a/src/lua/fiber.c b/src/lua/fiber.c
index 147add89b..289d240f6 100644
--- a/src/lua/fiber.c
+++ b/src/lua/fiber.c
@@ -178,20 +178,79 @@ lbox_fiber_id(struct lua_State *L)
 	return 1;
 }
 
+/**
+ * Lua fiber traceback context.
+ */
+struct lua_fiber_tb_ctx {
+	/* Lua stack to push values. */
+	struct lua_State *L;
+	/* Lua stack to trace. */
+	struct lua_State *R;
+	/* Current Lua frame. */
+	int lua_frame;
+	/* Count of traced frames (both C and Lua). */
+	int tb_frame;
+};
+
 #ifdef ENABLE_BACKTRACE
-static int
-fiber_backtrace_cb(int frameno, void *frameret, const char *func, size_t offset, void *cb_ctx)
+static void
+dump_lua_frame(struct lua_State *L, lua_Debug *ar, int tb_frame, int lua_frame)
 {
 	char buf[512];
-	int l = snprintf(buf, sizeof(buf), "#%-2d %p in ", frameno, frameret);
-	if (func)
-		snprintf(buf + l, sizeof(buf) - l, "%s+%zu", func, offset);
-	else
-		snprintf(buf + l, sizeof(buf) - l, "?");
-	struct lua_State *L = (struct lua_State*)cb_ctx;
-	lua_pushnumber(L, frameno + 1);
+	snprintf(buf, sizeof(buf), "LUA:#%d %s in %s at line %i",
+		 lua_frame + 1,
+		 ar->name != NULL ? ar->name : "(unnamed)",
+		 ar->source, ar->currentline);
+	lua_pushnumber(L, tb_frame);
 	lua_pushstring(L, buf);
 	lua_settable(L, -3);
+}
+
+static int
+fiber_backtrace_cb(int frameno, void *frameret, const char *func, size_t offset, void *cb_ctx)
+{
+	struct lua_fiber_tb_ctx *tb_ctx = (struct lua_fiber_tb_ctx *)cb_ctx;
+	struct lua_State *L = tb_ctx->L;
+	if (strstr(func, "lj_BC_FUNCC") == func) {
+		// LUA code.
+		lua_Debug ar;
+		while (tb_ctx->R && lua_getstack(tb_ctx->R, tb_ctx->lua_frame, &ar) > 0) {
+			// Skip all C-frames.
+			lua_getinfo(tb_ctx->R, "Sln", &ar);
+			if (*ar.what != 'C')
+				break;
+			if (ar.name != NULL) {
+				// Dump frame if it is a built-in call
+				tb_ctx->tb_frame++;
+				dump_lua_frame(L, &ar, tb_ctx->tb_frame,
+					       tb_ctx->lua_frame);
+			}
+			tb_ctx->lua_frame++;
+		}
+		while (tb_ctx->R && lua_getstack(tb_ctx->R, tb_ctx->lua_frame, &ar) > 0) {
+			// Trace Lua frames.
+			lua_getinfo(tb_ctx->R, "Sln", &ar);
+			if (*ar.what == 'C') {
+				break;
+			}
+			tb_ctx->tb_frame++;
+			dump_lua_frame(L, &ar, tb_ctx->tb_frame,
+				       tb_ctx->lua_frame);
+			tb_ctx->lua_frame++;
+		}
+	} else {
+		char buf[512];
+		int l = snprintf(buf, sizeof(buf), "C:#%d %p in ",
+				 frameno + 1, frameret);
+		if (func)
+			snprintf(buf + l, sizeof(buf) - l, "%s+%zu", func, offset);
+		else
+			snprintf(buf + l, sizeof(buf) - l, "?");
+		tb_ctx->tb_frame++;
+		lua_pushnumber(L, tb_ctx->tb_frame);
+		lua_pushstring(L, buf);
+		lua_settable(L, -3);
+	}
 	return 0;
 }
 #endif
@@ -229,10 +288,15 @@ lbox_fiber_statof(struct fiber *f, void *cb_ctx, bool backtrace)
 
 	if (backtrace) {
 #ifdef ENABLE_BACKTRACE
+		struct lua_fiber_tb_ctx tb_ctx;
+		tb_ctx.L = L;
+		tb_ctx.R = f->storage.lua.stack;
+		tb_ctx.lua_frame = 0;
+		tb_ctx.tb_frame = 0;
 		lua_pushstring(L, "backtrace");
 		lua_newtable(L);
-		if (f != fiber())
-			backtrace_foreach(fiber_backtrace_cb, &f->ctx, L);
+		backtrace_foreach(fiber_backtrace_cb,
+				  f != fiber() ? &f->ctx : NULL, &tb_ctx);
 		lua_settable(L, -3);
 #endif /* ENABLE_BACKTRACE */
 	}
diff --git a/test/app/fiber.result b/test/app/fiber.result
index 77144e661..1a7827fa1 100644
--- a/test/app/fiber.result
+++ b/test/app/fiber.result
@@ -849,6 +849,39 @@ f2:cancel()
 f3:cancel()
 ---
 ...
+function sf1() loop() end
+---
+...
+function sf2() sf1() end
+---
+...
+function sf3() sf2() end
+---
+...
+f1 = fiber.create(sf3)
+---
+...
+info = fiber.info()
+---
+...
+backtrace = info[f1:id()].backtrace
+---
+...
+bt_str = table.concat(backtrace, '\n')
+---
+...
+bt_str:find('sf1') ~= nil
+---
+- true
+...
+bt_str:find('loop') ~= nil
+---
+- true
+...
+bt_str:find('sf3') ~= nil
+---
+- true
+...
 -- # gh-666: nulls in output
 --
 getmetatable(fiber.info())
diff --git a/test/app/fiber.test.lua b/test/app/fiber.test.lua
index 98a136090..9df751cc8 100644
--- a/test/app/fiber.test.lua
+++ b/test/app/fiber.test.lua
@@ -334,6 +334,18 @@ f1:cancel()
 f2:cancel()
 f3:cancel()
 
+function sf1() loop() end
+function sf2() sf1() end
+function sf3() sf2() end
+f1 = fiber.create(sf3)
+
+info = fiber.info()
+backtrace = info[f1:id()].backtrace
+bt_str = table.concat(backtrace, '\n')
+bt_str:find('sf1') ~= nil
+bt_str:find('loop') ~= nil
+bt_str:find('sf3') ~= nil
+
 -- # gh-666: nulls in output
 --
 getmetatable(fiber.info())
-- 
2.19.0