[Tarantool-patches] [PATCH v2 corrected] Increase limits for debug.traceback

[Sergey Voinov]

Currently debug.traceback cuts out path prefixes
and removes intermediate frames. This makes it harder
to debug and navigate to files right from terminal.

This change increases traceback limits to 25 stack frames
and maximum source file name length to 128 characters.

There are also changes in main Tarantool trunk in
cmake/luajit.cmake (see corresponding commit for it).

Closes: #4581
---
 Changes in v2:
 - fixed code and test in accordance with review

 src/lj_debug.c                         |  8 +--
 src/luaconf.h                          | 14 ++++-
 test/tarantool-4581-traceback.test.lua | 79 ++++++++++++++++++++++++++
 3 files changed, 95 insertions(+), 6 deletions(-)
 create mode 100755 test/tarantool-4581-traceback.test.lua

diff --git a/src/lj_debug.c b/src/lj_debug.c
index 73bd196..e65eb05 100644
--- a/src/lj_debug.c
+++ b/src/lj_debug.c
@@ -332,11 +332,11 @@ void lj_debug_shortname(char *out, GCstr *str, BCLine line)
     strcpy(out, src);
   } else {  /* Output [string "string"] or [builtin:name]. */
     size_t len;  /* Length, up to first control char. */
-    for (len = 0; len < LUA_IDSIZE-12; len++)
+    for (len = 0; len < LUA_IDSIZE_ERR-12; len++)
       if (((const unsigned char *)src)[len] < ' ') break;
     strcpy(out, line == ~(BCLine)0 ? "[builtin:" : "[string \""); out += 9;
     if (src[len] != '\0') {  /* Must truncate? */
-      if (len > LUA_IDSIZE-15) len = LUA_IDSIZE-15;
+      if (len > LUA_IDSIZE_ERR-15) len = LUA_IDSIZE_ERR-15;
       strncpy(out, src, len); out += len;
       strcpy(out, "..."); out += 3;
     } else {
@@ -651,8 +651,8 @@ void lj_debug_dumpstack(lua_State *L, SBuf *sb, const char *fmt, int depth)
 #endif
 
 /* Number of frames for the leading and trailing part of a traceback. */
-#define TRACEBACK_LEVELS1	12
-#define TRACEBACK_LEVELS2	10
+#define TRACEBACK_LEVELS1	LUA_TRACEBACK_LEVELS1
+#define TRACEBACK_LEVELS2	LUA_TRACEBACK_LEVELS2
 
 LUALIB_API void luaL_traceback (lua_State *L, lua_State *L1, const char *msg,
 				int level)
diff --git a/src/luaconf.h b/src/luaconf.h
index 60cb928..69992b3 100644
--- a/src/luaconf.h
+++ b/src/luaconf.h
@@ -109,9 +109,19 @@
 #define LUA_MAXINPUT	512	/* Max. input line length. */
 #endif
 
+#ifndef LUA_TRACEBACK_LEVELS1
+# define LUA_TRACEBACK_LEVELS1	12
+#endif
+#ifndef LUA_TRACEBACK_LEVELS2
+# define LUA_TRACEBACK_LEVELS2	10
+#endif
+
 /* Note: changing the following defines breaks the Lua 5.1 ABI. */
-#define LUA_INTEGER	ptrdiff_t
-#define LUA_IDSIZE	60	/* Size of lua_Debug.short_src. */
+#define LUA_INTEGER		ptrdiff_t
+#ifndef LUA_IDSIZE
+# define LUA_IDSIZE		128 /* Size of lua_Debug.short_src. */
+#endif
+#define LUA_IDSIZE_ERR		60  /* Size of error message */
 /*
 ** Size of lauxlib and io.* on-stack buffers. Weird workaround to avoid using
 ** unreasonable amounts of stack space, but still retain ABI compatibility.
diff --git a/test/tarantool-4581-traceback.test.lua b/test/tarantool-4581-traceback.test.lua
new file mode 100755
index 0000000..595871b
--- /dev/null
+++ b/test/tarantool-4581-traceback.test.lua
@@ -0,0 +1,79 @@
+#!/usr/bin/env tarantool
+
+---
+--- gh-4581: Increase limits for debug.traceback
+---
+
+local test = require('tap').test('traceback test')
+test:plan(1)
+
+-- Currently there is no Lua way to detect the values of
+-- LUA_TRACEBACK_LEVEL1, LUA_TRACEBACK_LEVEL2, LUA_IDSIZE. Therefore
+-- taking into account the default values configured for Tarantool
+-- build and considering the existing testing pipeline we can hardcode
+-- the corresponding values within this test suite to check the output
+-- produced via debug.backtrace.
+local LUA_TRACEBACK_LEVEL1 = 25
+local LUA_TRACEBACK_LEVEL2 = 25
+
+local TRACEBACK_MSG1 = 'recursion limit reached!'
+local TRACEBACK_MSG2 = 'stack traceback:'
+local TRACEBACK_PATTERN = 'tarantool%-4581%-traceback%.test%.lua:[0-9]+: in .*'
+
+-- We use local output variable instead of returning function
+-- value recursively since luajit optimizes end recursion
+-- and in that case we would only get 2 stack frames for traceback
+local output
+
+-- Recursive function which generates stack frames for debug.traceback
+local function frec(rec_limit)
+    if rec_limit <= 0 then
+        output = debug.traceback(TRACEBACK_MSG1)
+        -- Strip path from the output and return it
+        output = output:gsub("[^\n]*/", "")
+    else
+        frec(rec_limit - 1)
+    end
+end
+
+-- Call debug.traceback with specified recursion depth
+frec(100)
+
+local test_ok = false
+
+-- Split output into strings
+local strings = {}
+for each in output:gmatch("([^\n]+)") do
+   table.insert(strings, each)
+end
+
+-- Total output string count
+local count = 0
+    + 2 -- header
+    + (LUA_TRACEBACK_LEVEL1-1) -- first part
+    + 1 -- three dots
+    + (LUA_TRACEBACK_LEVEL2) -- second part
+
+-- Check output strings
+if count == table.getn(strings) then
+    for i = 1,count,1 do
+        local pattern
+
+        if i == 1 then 
+            pattern = TRACEBACK_MSG1
+        elseif i == 2 then 
+            pattern = TRACEBACK_MSG2
+        elseif i ~= LUA_TRACEBACK_LEVEL1 + 2 then
+            pattern = TRACEBACK_PATTERN
+        else
+            pattern = '%.%.%.'
+        end
+
+        test_ok = string.match(strings[i], pattern) ~= nil
+        if not test_ok then
+            break
+        end
+    end
+end
+
+test:is(test_ok, true)
-- 
2.17.1