Added elipsis in traceback fn and test cases for that

spec/traceback/anon_lua/anon_lua.pln

@@ -0,0 +1,12 @@
+-- Copyright (c) 2024, The Pallene Developers
+-- Pallene is licensed under the MIT license.
+-- Please refer to the LICENSE and AUTHORS files for details
+-- SPDX-License-Identifier: MIT
+
+local mod: module = {}
+
+function mod.call_anon_lua_fn(callback: () -> ())
+    callback()
+end
+
+return mod

spec/traceback/anon_lua/main.lua

@@ -0,0 +1,15 @@
+-- Copyright (c) 2024, The Pallene Developers
+-- Pallene is licensed under the MIT license.
+-- Please refer to the LICENSE and AUTHORS files for details
+-- SPDX-License-Identifier: MIT
+
+local anon = require "spec.traceback.anon_lua.anon_lua"
+
+local function wrapper()
+    anon.call_anon_lua_fn(function()
+        error "Error from an anonymous Lua fn!"
+    end)
+end
+
+-- luacheck: globals pallene_tracer_debug_traceback
+xpcall(wrapper, pallene_tracer_debug_traceback)

spec/traceback/depth_recursion/main.lua

@@ -3,7 +3,7 @@
 -- Please refer to the LICENSE and AUTHORS files for details
 -- SPDX-License-Identifier: MIT
 
-local pallene = require 'spec.traceback.depth_recursion.depth_recursion'
+local pallene = require "spec.traceback.depth_recursion.depth_recursion"
 
 -- luacheck: globals lua_fn
 function lua_fn(depth)

spec/traceback/module_lua/main.lua

@@ -3,8 +3,8 @@
 -- Please refer to the LICENSE and AUTHORS files for details
 -- SPDX-License-Identifier: MIT
 
-local another_module = require 'spec.traceback.module_lua.another_module'
-local pallene = require 'spec.traceback.module_lua.module_lua'
+local another_module = require "spec.traceback.module_lua.another_module"
+local pallene = require "spec.traceback.module_lua.module_lua"
 
 -- luacheck: globals lua_1
 function lua_1()

spec/traceback/module_pallene/main.lua

@@ -3,12 +3,12 @@
 -- Please refer to the LICENSE and AUTHORS files for details
 -- SPDX-License-Identifier: MIT
 
-local pallene = require 'spec.traceback.module_pallene.module_pallene'
-local pallene_alt = require 'spec.traceback.module_pallene.module_pallene_alt'
+local pallene = require "spec.traceback.module_pallene.module_pallene"
+local pallene_alt = require "spec.traceback.module_pallene.module_pallene_alt"
 
 -- luacheck: globals lua_2
 function lua_2()
-    error "There's an error in everyday life. Shame!"
+    error "There's an error in everyday life. Alas!"
 end
 
 -- luacheck: globals lua_1

spec/traceback/rect/main.lua

@@ -3,7 +3,7 @@
 -- Please refer to the LICENSE and AUTHORS files for details
 -- SPDX-License-Identifier: MIT
 
-local rect = require 'spec.traceback.rect.rect'
+local rect = require "spec.traceback.rect.rect"
 
 -- Should be local.
 -- Making it global so that it is visible in the traceback.

spec/traceback/stack_overflow/main.lua

@@ -0,0 +1,19 @@
+-- Copyright (c) 2024, The Pallene Developers
+-- Pallene is licensed under the MIT license.
+-- Please refer to the LICENSE and AUTHORS files for details
+-- SPDX-License-Identifier: MIT
+
+local so = require "spec.traceback.stack_overflow.stack_overflow"
+
+-- luacheck: globals please_dont_overflow
+function please_dont_overflow()
+    so.no_overflow(please_dont_overflow)
+end
+
+-- luacheck: globals wrapper
+function wrapper()
+    please_dont_overflow()
+end
+
+-- luacheck: globals pallene_tracer_debug_traceback
+xpcall(wrapper, pallene_tracer_debug_traceback)

spec/traceback/stack_overflow/stack_overflow.pln

@@ -0,0 +1,12 @@
+-- Copyright (c) 2024, The Pallene Developers
+-- Pallene is licensed under the MIT license.
+-- Please refer to the LICENSE and AUTHORS files for details
+-- SPDX-License-Identifier: MIT
+
+local mod: module = {}
+
+function mod.no_overflow(callback: () -> ())
+    callback()
+end
+
+return mod

spec/traceback_spec.lua

@@ -57,7 +57,7 @@ end)
 
 it("Multi-module Pallene", function()
     assert_test("module_pallene", [[
-Runtime error: spec/traceback/module_pallene/main.lua:11: There's an error in everyday life. Shame!
+Runtime error: spec/traceback/module_pallene/main.lua:11: There's an error in everyday life. Alas!
 Stack traceback:
     C: in function 'error'
     spec/traceback/module_pallene/main.lua:11: in function 'lua_2'
@@ -94,3 +94,46 @@ Stack traceback:
 ]])
 end)
 
+it("Stack overflow", function()
+    assert_test("stack_overflow", [[
+Runtime error: C stack overflow
+Stack traceback:
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+
+    ... (Skipped 379 frames) ...
+
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/stack_overflow.pln:8: in function 'no_overflow'
+    spec/traceback/stack_overflow/main.lua:10: in function 'please_dont_overflow'
+    spec/traceback/stack_overflow/main.lua:15: in function 'wrapper'
+    C: in function 'xpcall'
+    spec/traceback/stack_overflow/main.lua:19: in <main>
+    C: in function '<?>'
+]])
+end)
+
+it("Anonymous lua functions", function()
+    assert_test("anon_lua", [[
+Runtime error: spec/traceback/anon_lua/main.lua:10: Error from an anonymous Lua fn!
+Stack traceback:
+    C: in function 'error'
+    spec/traceback/anon_lua/main.lua:10: in function '<?>'
+    spec/traceback/anon_lua/anon_lua.pln:8: in function 'call_anon_lua_fn'
+    spec/traceback/anon_lua/main.lua:9: in function '<?>'
+    C: in function 'xpcall'
+    spec/traceback/anon_lua/main.lua:15: in <main>
+    C: in function '<?>'
+]])
+end)

src/pallene/pallenelib.lua

@@ -76,6 +76,13 @@ return [==[
 /* Pallene stack reference entry for the registry. */
 #define PALLENE_TRACER_STACK_ENTRY      "__PALLENE_TRACER_STACK"
 
+/* Traceback elipsis threshold. */
+#define PALLENE_TRACEBACK_TOP_THRESHOLD      10
+/* This should always be 2 fewer than top threshold, for symmetry.
+   Becuase we will always have 2 tail frames lingering around at
+   at the end which is not captured by '_countlevels'. */
+#define PALLENE_TRACEBACK_BOTTOM_THRESHOLD    8
+
 /* PALLENE TRACER RELATED DATA-STRUCTURES. */
 
 /* Whether the frame is a Pallene->Pallene or Lua->Pallene call. */
@@ -237,6 +244,58 @@ static bool _pgf_name(lua_State *L) {
     return false;
 }
 
+/* Returns the maximum number of levels in Lua stack. */
+static int _countlevels (lua_State *L) {
+    lua_Debug ar;
+    int li = 1, le = 1;
+
+    /* Find an upper bound */
+    while (lua_getstack(L, le, &ar)) {
+        li = le, le *= 2;
+    }
+
+    /* Do a binary search */
+    while (li < le) {
+        int m = (li + le)/2;
+
+        if (lua_getstack(L, m, &ar)) li = m + 1;
+        else le = m;
+    }
+
+    return le - 1;
+}
+
+/* Counts the number of white and black frames in the Pallene call stack. */
+static void _countframes(pt_frame_t *frame, int *mwhite, int *mblack) {
+    *mwhite = *mblack = 0;
+
+    while(frame != NULL) {
+        *mwhite += (frame->type == PALLENE_TRACER_FRAME_TYPE_C);
+        *mblack += (frame->type == PALLENE_TRACER_FRAME_TYPE_LUA);
+        frame = frame->prev;
+    }
+}
+
+/* Responsible for printing and controlling some of the traceback fn parameters. */
+static void _dbg_print(const char *buf, bool *elipsis, int *pframes, int nframes) {
+    /* We have printed the frame, even tho it might not be visible ;). */
+    (*pframes)++;
+
+    /* Should we print? Are we in the point in top or bottom printing threshold? */
+    bool should_print = (*pframes <= PALLENE_TRACEBACK_TOP_THRESHOLD)
+        || ((nframes - *pframes) <= PALLENE_TRACEBACK_BOTTOM_THRESHOLD);
+
+    if(should_print)
+        fprintf(stderr, buf);
+    else if(*elipsis) {
+        fprintf(stderr, "\n    ... (Skipped %d frames) ...\n\n",
+            nframes - (PALLENE_TRACEBACK_TOP_THRESHOLD
+            + PALLENE_TRACEBACK_BOTTOM_THRESHOLD));
+
+        *elipsis = false;
+    }
+}
+
 /* Private routines end. */
 
 static void pallene_tracer_frameenter(pt_cont_t *cont, pt_frame_t *restrict frame) {
@@ -266,14 +325,35 @@ static void pallene_tracer_frameexit(pt_cont_t *cont) {
     cont->stack = cont->stack->prev;
 }
 
+/* Helper macro specific to this function only :). */
+#define DBG_PRINT() _dbg_print(buf, &elipsis, &pframes, nframes)
 static int pallene_tracer_debug_traceback(lua_State *L) {
-    const char *message = lua_tostring(L, 1);
-    fprintf(stderr, "Runtime error: %s\nStack traceback:\n", message);
-
     lua_getfield(L, LUA_REGISTRYINDEX, PALLENE_TRACER_STACK_ENTRY);
     pt_frame_t *stack = ((pt_cont_t *) lua_touserdata(L, -1))->stack;
     lua_pop(L, 1);
 
+    /* Max number of white and black frames. */
+    int mwhite, mblack;
+    _countframes(stack, &mwhite, &mblack);
+    /* Max levels of Lua stack. */
+    int mlevel = _countlevels(L);
+
+    /* Total frames we are going to print. */
+    /* Black frames are used for switching and we will start from
+       Lua stack level 1. */
+    int nframes = mlevel + mwhite - mblack - 1;
+    /* Amount of frames printed. */
+    int pframes = 0;
+    /* Should we print elipsis? */
+    bool elipsis = nframes > (PALLENE_TRACEBACK_TOP_THRESHOLD
+        + PALLENE_TRACEBACK_BOTTOM_THRESHOLD);
+
+    /* Buffer to store a single frame line to be printed. */
+    char buf[1024];
+
+    const char *message = lua_tostring(L, 1);
+    fprintf(stderr, "Runtime error: %s\nStack traceback:\n", message);
+
     lua_Debug ar;
     int top = lua_gettop(L);
     int level = 1;
@@ -294,9 +374,10 @@ static int pallene_tracer_debug_traceback(lua_State *L) {
                 if(lua_tocfunction(L, -1) == check->shared.frame_sig) {
                     /* Now print all the frames in Pallene stack. */
                     while(stack != check) {
-                        fprintf(stderr, "    %s:%d: in function '%s'\n",
+                        sprintf(buf, "    %s:%d: in function '%s'\n",
                             stack->shared.details->mod_name,
                             stack->line, stack->shared.details->fn_name);
+                        DBG_PRINT();
 
                         stack = stack->prev;
                     }
@@ -317,7 +398,8 @@ static int pallene_tracer_debug_traceback(lua_State *L) {
                 lua_pushfstring(L, "%s", lua_tostring(L, -1));
             else lua_pushliteral(L, "<?>");
 
-            fprintf(stderr, "    C: in function '%s'\n", lua_tostring(L, -1));
+            sprintf(buf, "    C: in function '%s'\n", lua_tostring(L, -1));
+            DBG_PRINT();
         } else {
             /* It's a Lua frame. */
 
@@ -332,15 +414,17 @@ static int pallene_tracer_debug_traceback(lua_State *L) {
                 lua_pushfstring(L, "function '%s'", lua_tostring(L, -1));
             else lua_pushliteral(L, "function '<?>'");
 
-            fprintf(stderr, "    %s:%d: in %s\n", ar.short_src,
+            sprintf(buf, "    %s:%d: in %s\n", ar.short_src,
                 ar.currentline, lua_tostring(L, -1));
+            DBG_PRINT();
         }
 
         lua_settop(L, top);
     }
 
     return 0;
 }
+#undef DBG_PRINT
 
 static pt_cont_t *pallene_tracer_init(lua_State *L) {
     pt_cont_t *cont = NULL;