From ef5195dee92732408466a9cc8dd48a63ff46667b Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Wed, 16 Mar 2022 21:19:19 -0700
Subject: [PATCH] simplify function call instrumentation

src/ldo.c now has a minimal diff with Lua 5.1.

It might be a bit slower than it was before, but not noticeably so..

This approach doesn't support indirect calls.
---
 src/ldo.c    | 33 +--------------------------------
 src/teliva.c | 25 +++++++++++++++++++------
 src/teliva.h |  3 ---
 3 files changed, 20 insertions(+), 41 deletions(-)

diff --git a/src/ldo.c b/src/ldo.c
index 39f8cbe..1857e0d 100644
--- a/src/ldo.c
+++ b/src/ldo.c
@@ -29,7 +29,6 @@
 #include "lundump.h"
 #include "lvm.h"
 #include "lzio.h"
-#include "teliva.h"
 
 
 
@@ -256,37 +255,7 @@ static StkId tryfuncTM (lua_State *L, StkId func) {
 }
 
 
-/* based on getfuncname */
-extern Instruction symbexec (const Proto *pt, int lastpc, int reg);
-extern int luaL_newmetatable (lua_State *L, const char *tname);
-void record_metadata_about_function_call (lua_State *L, CallInfo *ci) {
-  if (!isLua(ci))
-    return;
-  if (ci->tailcalls > 0)
-    return;
-  if (!isLua(ci - 1))
-    return;
-  ci--;  /* calling function */
-  if (ci == L->ci)
-    ci->savedpc = L->savedpc;
-  int pc = cast(int, ci->savedpc - ci_func(ci)->l.p->code) - 1;
-  lua_assert(pc != -1);  // TODO: lua_assert not triggering
-  Instruction i = ci_func(ci)->l.p->code[pc];
-  if (GET_OPCODE(i) != OP_CALL && GET_OPCODE(i) != OP_TAILCALL &&
-      GET_OPCODE(i) != OP_TFORLOOP)
-    return;
-  Proto *p = ci_func(ci)->l.p;
-  i = symbexec(p, pc, GETARG_A(i));  /* previous instruction that writes to call's RA */
-  if (GET_OPCODE(i) != OP_GETGLOBAL)
-    return;
-  int g = GETARG_Bx(i);  /* global index */
-  lua_assert(ttisstring(&p->k[g]));
-  int call_graph_depth = ci - L->base_ci;
-  const char* function_name = svalue(&p->k[g]);
-  assign_call_graph_depth_to_name(L, call_graph_depth, function_name);
-  save_caller(L, function_name, call_graph_depth);
-}
-
+extern void record_metadata_about_function_call (lua_State *L, CallInfo *ci);
 
 #define inc_ci(L) \
   ((L->ci == L->end_ci) ? growCI(L) : \
diff --git a/src/teliva.c b/src/teliva.c
index 1bc06d5..3d20267 100644
--- a/src/teliva.c
+++ b/src/teliva.c
@@ -13,6 +13,9 @@
 #include "lua.h"
 #include "lauxlib.h"
 #include "lualib.h"
+
+#undef getstr
+#include "lstate.h"
 #include "teliva.h"
 #include "tlv.h"
 
@@ -341,11 +344,21 @@ static void save_caller_as(lua_State* L, const char* name, const char* caller_na
   lua_pop(L, 1);  // table of caller tables
 }
 
-void save_caller(lua_State* L, const char* name, int call_graph_depth) {
-  lua_Debug ar;
-  lua_getstack(L, 1, &ar);
-  lua_getinfo(L, "n", &ar);
-  if (ar.name) save_caller_as(L, name, ar.name);
+void record_metadata_about_function_call (lua_State *L, CallInfo *ci) {
+  lua_Debug f;
+  lua_getstack(L, 0, &f);
+  lua_getinfo(L, "n", &f);
+  long int call_depth = ci - L->base_ci;
+  /* note to self: the function pointer is at ci_func(ci) */
+  if (f.name) {
+    assign_call_graph_depth_to_name(L, call_depth, f.name);
+    if (call_depth <= 1) return;
+    lua_Debug caller_f;
+    lua_getstack(L, 1, &caller_f);
+    lua_getinfo(L, "n", &caller_f);
+    if (caller_f.name)
+      save_caller_as(L, f.name, caller_f.name);
+  }
 }
 
 static void clear_caller(lua_State* L) {
@@ -496,7 +509,7 @@ restart:
   y += 2;
   mvprintw(y, 0, "functions: ");
   y++;
-  for (int depth = /*ignore call_main*/2; ; ++depth) {
+  for (int depth = /*ignore callers of main*/3; ; ++depth) {
     mvaddstr(y, 0, "                ");
     bool drew_anything = false;
     index_within_level = 0;
diff --git a/src/teliva.h b/src/teliva.h
index 2e79956..5808382 100644
--- a/src/teliva.h
+++ b/src/teliva.h
@@ -165,10 +165,7 @@ extern void save_editor_state(int rowoff, int coloff, int cy, int cx);
 int editor_view_in_progress(lua_State* L);
 
 extern void assign_call_graph_depth_to_name(lua_State* L, int depth, const char* name);
-extern char* get_caller(lua_State* L);
-extern void save_caller(lua_State* L, const char* name, int call_graph_depth);
 extern void draw_callers_of_current_definition(lua_State* L);
-extern char* get_caller_of_caller(lua_State* L);
 
 extern void append_to_audit_log(lua_State* L, const char* buffer);