From 90e493fa3a7fee51123078d02f988fa6d1f07a84 Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Thu, 9 Jan 2025 20:26:14 +0300
Subject: [PATCH] engine: common: add Host_ExitInMain function that will force
 engine return from Host_Main() function, essentially making engine gracefully
 exit on Android

In future, this might be used everywhere, so users would be able to add custom
cleanup in some advanced game_launch implementation, on any platform.
---
 engine/common/common.h |  1 +
 engine/common/host.c   | 26 ++++++++++++++++++++++++++
 engine/common/system.c | 10 ++++++++++
 3 files changed, 37 insertions(+)

diff --git a/engine/common/common.h b/engine/common/common.h
index 4a3066b6..95af6384 100644
--- a/engine/common/common.h
+++ b/engine/common/common.h
@@ -559,6 +559,7 @@ void Host_Error( const char *error, ... ) FORMAT_CHECK( 1 );
 void Host_ValidateEngineFeatures( uint32_t mask, uint32_t features );
 void Host_Frame( double time );
 void Host_Credits( void );
+void Host_ExitInMain( void );
 
 //
 // host_state.c
diff --git a/engine/common/host.c b/engine/common/host.c
index c4d814cf..0c9847a2 100644
--- a/engine/common/host.c
+++ b/engine/common/host.c
@@ -43,6 +43,27 @@ GNU General Public License for more details.
 static pfnChangeGame	pChangeGame = NULL;
 host_parm_t		host;	// host parms
 
+#if XASH_ANDROID
+static jmp_buf return_from_main_buf;
+
+/*
+===============
+Host_ExitInMain
+
+On some platforms (e.g. Android) we can't exit with exit(3) as calling it would
+kill wrapper process (e.g. app_process) too early, before all resources would
+be freed, contexts released, files closed, etc, etc...
+
+To fix this, we create jmp_buf in Host_Main function, when jumping into with
+non-zero value will immediately return from it with `error_on_exit`.
+===============
+*/
+void Host_ExitInMain( void )
+{
+	longjmp( return_from_main_buf, 1 );
+}
+#endif // XASH_ANDROID
+
 #ifdef XASH_ENGINE_TESTS
 struct tests_stats_s tests_stats;
 #endif
@@ -1319,6 +1340,11 @@ int EXPORT Host_Main( int argc, char **argv, const char *progname, int bChangeGa
 	// check after all configs were executed
 	HPAK_CheckIntegrity( hpk_custom_file.string );
 
+#if XASH_ANDROID
+	if( setjmp( return_from_main_buf ))
+		return error_on_exit;
+#endif // XASH_ANDROID
+
 	// main window message loop
 	while( !host.crashed )
 	{
diff --git a/engine/common/system.c b/engine/common/system.c
index 46cf816c..765a4d26 100644
--- a/engine/common/system.c
+++ b/engine/common/system.c
@@ -420,6 +420,12 @@ void Sys_Error( const char *error, ... )
 _exit->_Exit->asm._exit->_exit
 As we do not need atexit(), just throw hidden exception
 */
+
+// Hey, you, making an Emscripten port!
+// What if we're not supposed to use exit() on Emscripten and instead we should
+// exit from the main() function? Would this fix this bug? Test this case, pls.
+#error "Read the comment above"
+
 #include <emscripten.h>
 #define exit my_exit
 void my_exit(int ret)
@@ -438,7 +444,11 @@ Sys_Quit
 void Sys_Quit( const char *reason )
 {
 	Host_ShutdownWithReason( reason );
+#if XASH_ANDROID
+	Host_ExitInMain();
+#else
 	exit( error_on_exit );
+#endif
 }
 
 /*