From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Wed, 30 Jan 2019 18:04:32 +0000 (+0100)
Subject: lua_error_p(): print whole stack trace
X-Git-Tag: v4.0.0~38^2~2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c06010be0ed32818df8f4cc7badcc372225508ff;p=thirdparty%2Fknot-resolver.git

lua_error_p(): print whole stack trace

We use a function that's not in lua 5.1,
but it's been present in luajit since 2.0.0:
https://github.com/LuaJIT/LuaJIT/commit/fcddd5a3a
---

diff --git a/daemon/bindings/impl.c b/daemon/bindings/impl.c
index 4bcc4315a..b4671a07f 100644
--- a/daemon/bindings/impl.c
+++ b/daemon/bindings/impl.c
@@ -15,6 +15,7 @@
  */
 
 #include <lua.h>
+#include <lauxlib.h>
 #include <string.h>
 
 /* Each of these just creates the correspondingly named lua table of functions. */
@@ -46,26 +47,21 @@ void kr_bindings_register(lua_State *L)
 
 void lua_error_p(lua_State *L, const char *fmt, ...)
 {
-	/* Push a string describing location in the "parent" lua function. */
-	lua_Debug d;
-	lua_getstack(L, 1, &d);
-	lua_getinfo(L, "Sln", &d);
-	if (strncmp(d.short_src, "[", 1) != 0) {
-		lua_pushstring(L, d.short_src);
-		lua_pushstring(L, ":");
-		lua_pushnumber(L, d.currentline);
-		lua_pushstring(L, ": error: ");
-		lua_concat(L, 4);
-	} else {
-		lua_pushstring(L, "error: ");
+	/* Push formatted custom message, prepended with "ERROR: ". */
+	lua_pushliteral(L, "ERROR: ");
+	{
+		va_list args;
+		va_start(args, fmt);
+		lua_pushvfstring(L, fmt, args);
+		va_end(args);
 	}
-	/* Push formatted custom message. */
-	va_list args;
-	va_start(args, fmt);
-	lua_pushvfstring(L, fmt, args);
-	va_end(args);
-	/* Concatenate the two and throw a lua error. */
-	lua_concat(L,  2);
+	lua_concat(L, 2);
+	/* Add a stack trace and throw the result as a lua error. */
+	luaL_traceback(L, L, lua_tostring(L, -1), 0);
 	lua_error(L);
+	/* TODO: we might construct a little more friendly trace by using luaL_where().
+	 * In particular, in case the error happens in a function that was called
+	 * directly from a config file (the most common case), there isn't much need
+	 * to format the trace in this heavy way. */
 }
 
diff --git a/daemon/bindings/impl.h b/daemon/bindings/impl.h
index a9dd3b52c..d5dfff314 100644
--- a/daemon/bindings/impl.h
+++ b/daemon/bindings/impl.h
@@ -39,12 +39,22 @@
 #define STR(s) STRINGIFY_TOKEN(s)
 #define STRINGIFY_TOKEN(s) #s
 
-/** @internal Annotate for static checkers. */
-KR_NORETURN int lua_error(lua_State *L);
-
-/** Throw a formatted lua error.  It doesn't return. */
+/** Throw a formatted lua error.
+ *
+ * The message will get prefixed by "ERROR: " and supplemented by stack trace.
+ * \return never!  It calls lua_error().
+ *
+ * Example:
+	ERROR: not a valid pin_sha256: 'a1Z/3ek=', raw length 5 instead of 32
+	stack traceback:
+		[C]: in function 'tls_client'
+		/PathToPREFIX/lib/kdns_modules/policy.lua:175: in function 'TLS_FORWARD'
+		/PathToConfig.lua:46: in main chunk
+ */
 KR_PRINTF(2) KR_NORETURN KR_COLD
 void lua_error_p(lua_State *L, const char *fmt, ...);
+/** @internal Annotate for static checkers. */
+KR_NORETURN int lua_error(lua_State *L);
 
 /** Shortcut for common case. */
 static inline void lua_error_maybe(lua_State *L, int err)