From 27292f0d9ed90340792d4d065fefd2e4e248e4bd Mon Sep 17 00:00:00 2001
From: sanine-a <sanine.not@pm.me>
Date: Sat, 24 Oct 2020 19:54:18 -0500
Subject: add honey_lua_pcall with traceback ability

---
 src/common.h    |  8 ++++++++
 src/honey_lua.c | 40 ++++++++++++++++++++++++++++++++++++++++
 src/main.c      |  6 +++---
 3 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/src/common.h b/src/common.h
index 47b7ee4..63962db 100644
--- a/src/common.h
+++ b/src/common.h
@@ -153,4 +153,12 @@ void honey_lua_create_table(lua_State* L,
 			    honey_lua_element* elements,
 			    unsigned int n_elements);
 
+/** @brief Get the traceback for use after an error.
+ */
+int honey_lua_traceback(lua_State* L);
+
+/** @brief Wrapper for lua_pcall that uses a honey_lua_traceback as an error handler.
+ */
+int honey_lua_pcall(lua_State* L, int nargs, int nret);
+
 #endif
diff --git a/src/honey_lua.c b/src/honey_lua.c
index f397872..ded2a91 100644
--- a/src/honey_lua.c
+++ b/src/honey_lua.c
@@ -190,3 +190,43 @@ void honey_lua_push_element(lua_State* L, honey_lua_element element)
         break;
     }
 }
+
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+int honey_lua_traceback(lua_State* L)
+{
+    if (!lua_isstring(L, 1))
+        /* 'message' is not a string, keep intact. */
+        return 1;
+
+    lua_getglobal(L, "debug");
+    if (!lua_istable(L, -1)) {
+        lua_pop(L, 1);
+        return 1;
+    }
+
+    lua_getfield(L, -1, "traceback");
+    if (!lua_isfunction(L, -1)) {
+        lua_pop(L, 2);
+        return 1;
+    }
+
+    lua_pushvalue(L, 1);
+    lua_pushinteger(L, 2);
+    lua_call(L, 2, 1);
+    return 1;
+}
+
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+int honey_lua_pcall(lua_State* L, int nargs, int nret)
+{
+    int traceback_pos = lua_gettop(L) - nargs;
+    lua_pushcfunction(L, honey_lua_traceback);
+    lua_insert(L, traceback_pos);
+
+    int result = lua_pcall(L, nargs, nret, traceback_pos);
+    lua_remove(L, traceback_pos);
+    return result;
+}
+    
diff --git a/src/main.c b/src/main.c
index 14037fb..8d710a7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -23,7 +23,7 @@ int main(int argc, char** argv)
     }
     
     if (luaL_loadfile(L, script) == 0) {
-        if (!lua_pcall(L, 0, 1, 0) == 0) {
+        if (!honey_lua_pcall(L, 0, 1) == 0) {
             const char* error = lua_tostring(L, -1);
             fprintf(stderr, "[honey] ERROR: %s\n", error);
             return 1;
@@ -50,7 +50,7 @@ int main(int argc, char** argv)
         if (update_callback != LUA_NOREF) {
             lua_rawgeti(L, LUA_REGISTRYINDEX, update_callback);
             lua_pushnumber(L, dt);
-            int result = lua_pcall(L, 1, 0, 0);
+            int result = honey_lua_pcall(L, 1, 0);
             if (result != 0) {
                 const char* error = lua_tostring(L, -1);
                 fprintf(stderr, "[honey] ERROR: %s\n", error);
@@ -60,7 +60,7 @@ int main(int argc, char** argv)
 
         if (draw_callback != LUA_NOREF) {
             lua_rawgeti(L, LUA_REGISTRYINDEX, draw_callback);
-            int result = lua_pcall(L, 0, 0, 0);
+            int result = honey_lua_pcall(L, 0, 0);
             if (result != 0) {
                 const char* error = lua_tostring(L, -1);
                 fprintf(stderr, "[honey] ERROR: %s\n", error);
-- 
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