From 546e333a3cd71049dfc8e05570f8dd08fa61830c Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Sun, 3 Jan 2016 23:04:00 +0900
Subject: [PATCH] Allow Sys_Error to be hooked.

This makes debugging builtins that wrap normal functions a little easier by
giving a progs dump when such an error occurs.
---
 include/QF/sys.h        |  5 +++++
 libs/gamecode/pr_exec.c | 19 +++++++++++++++----
 libs/util/sys.c         | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/include/QF/sys.h b/include/QF/sys.h
index 1fe994c94..8bbb08781 100644
--- a/include/QF/sys.h
+++ b/include/QF/sys.h
@@ -63,13 +63,18 @@ int Sys_isdir (const char *path);
 int Sys_mkdir (const char *path);
 
 typedef void (*sys_printf_t) (const char *fmt, va_list args);
+typedef void (*sys_error_t) (void *data);
 
 void Sys_SetStdPrintf (sys_printf_t func);
 void Sys_SetErrPrintf (sys_printf_t func);
 
+void Sys_PushErrorHandler (sys_error_t func, void *data);
+void Sys_PopErrorHandler (void);
+
 void Sys_Print (FILE *stream, const char *fmt, va_list args);
 void Sys_Printf (const char *fmt, ...) __attribute__((format(printf,1,2)));
 void Sys_Error (const char *error, ...) __attribute__((format(printf,1,2), noreturn));
+void Sys_FatalError (const char *error, ...) __attribute__((format(printf,1,2), noreturn));
 void Sys_Quit (void) __attribute__((noreturn));
 void Sys_Shutdown (void);
 void Sys_RegisterShutdown (void (*func) (void));
diff --git a/libs/gamecode/pr_exec.c b/libs/gamecode/pr_exec.c
index 0ebf7dbef..579992271 100644
--- a/libs/gamecode/pr_exec.c
+++ b/libs/gamecode/pr_exec.c
@@ -328,6 +328,14 @@ signal_hook (int sig, void *data)
 	return 0;
 }
 
+static void
+error_handler (void *data)
+{
+	progs_t    *pr = (progs_t *) data;
+	PR_DumpState (pr);
+	fflush (stdout);
+}
+
 VISIBLE int
 PR_CallFunction (progs_t *pr, func_t fnum)
 {
@@ -370,11 +378,11 @@ PR_ExecuteProgram (progs_t * pr, func_t fnum)
 	startprofile = profile = 0;
 
 	Sys_PushSignalHook (signal_hook, pr);
+	Sys_PushErrorHandler (error_handler, pr);
 
 	if (!PR_CallFunction (pr, fnum)) {
 		// called a builtin instead of progs code
-		Sys_PopSignalHook ();
-		return;
+		goto exit_program;
 	}
 	st = pr->pr_statements + pr->pr_xstatement;
 
@@ -964,8 +972,8 @@ op_call:
 				if (pr->pr_depth == exitdepth) {
 					if (pr->pr_trace && pr->pr_depth <= pr->pr_trace_depth)
 						pr->pr_trace = false;
-					Sys_PopSignalHook ();
-					return;					// all done
+					// all done
+					goto exit_program;
 				}
 				break;
 			case OP_STATE:
@@ -1116,4 +1124,7 @@ op_call:
 			PR_RunError (pr, "watchpoint hit: %d -> %d", old_val.integer_var,
 						 watch->integer_var);
 	}
+exit_program:
+	Sys_PopErrorHandler ();
+	Sys_PopSignalHook ();
 }
diff --git a/libs/util/sys.c b/libs/util/sys.c
index 4e2e111e2..1b6a9c269 100644
--- a/libs/util/sys.c
+++ b/libs/util/sys.c
@@ -79,6 +79,7 @@
 
 #include "qfalloca.h"
 
+#include "QF/alloc.h"
 #include "QF/cmd.h"
 #include "QF/cvar.h"
 #include "QF/dstring.h"
@@ -107,8 +108,17 @@ typedef struct shutdown_list_s {
 	void (*func)(void);
 } shutdown_list_t;
 
+typedef struct error_handler_s {
+	struct error_handler_s *next;
+	sys_error_t func;
+	void       *data;
+} error_handler_t;
+
 static shutdown_list_t *shutdown_list;
 
+static error_handler_t *error_handler_freelist;
+static error_handler_t *error_handler;
+
 #ifndef _WIN32
 static int  do_stdin = 1;
 qboolean    stdin_ready;
@@ -493,6 +503,31 @@ Sys_Quit (void)
 	exit (0);
 }
 
+VISIBLE void
+Sys_PushErrorHandler (sys_error_t func, void *data)
+{
+	error_handler_t *eh;
+	ALLOC (16, error_handler_t, error_handler, eh);
+	eh->func = func;
+	eh->data = data;
+	eh->next = error_handler;
+	error_handler = eh;
+}
+
+VISIBLE void
+Sys_PopErrorHandler (void)
+{
+	error_handler_t *eh;
+
+	if (!error_handler) {
+		Sys_Error ("Sys_PopErrorHandler: no handler to pop");
+	}
+	eh = error_handler;
+	error_handler = eh->next;
+	FREE (error_handler, eh);
+}
+
+
 VISIBLE void
 Sys_Error (const char *error, ...)
 {
@@ -515,6 +550,10 @@ Sys_Error (const char *error, ...)
 	sys_err_printf_function (error, args);
 	va_end (args);
 
+	if (error_handler) {
+		error_handler->func (error_handler->data);
+	}
+
 	Sys_Shutdown ();
 
 	if (sys_err_printf_function != Sys_ErrPrintf) {