From b8432a21a5d4868ca0c85158f8caec7e4f2e6e11 Mon Sep 17 00:00:00 2001
From: darkstar <michael@drueing.de>
Date: Wed, 21 Feb 2018 23:33:16 +0100
Subject: [PATCH] SOUND: Use alloca() for stack allocations

Using an array with a variable size is a gcc extension and is not
portable. The _alloca() method works but should be reworked at some point
to make use of a static buffer
---
 src/sound/snd_adlibgold.c | 10 ++++++++++
 src/sound/snd_dbopl.cc    | 26 ++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/src/sound/snd_adlibgold.c b/src/sound/snd_adlibgold.c
index 3ae661e..a21aa7a 100644
--- a/src/sound/snd_adlibgold.c
+++ b/src/sound/snd_adlibgold.c
@@ -683,7 +683,17 @@ void adgold_timer_poll(void *p)
 static void adgold_get_buffer(int32_t *buffer, int len, void *p)
 {
         adgold_t *adgold = (adgold_t *)p;
+#ifdef _MSC_VER
+        /* TODO: Fix this to use a static buffer */
+        if (len > 512 * 1024)
+        {
+            pclog("adgold_get_buffer: possible stack overflow detected. Buffer size was %d bytes", 2 * len);
+            return;
+        }
+        int16_t *adgold_buffer = (int16_t *)_alloca(len * 2);
+#else
         int16_t adgold_buffer[len*2];
+#endif
         
         int c;
 
diff --git a/src/sound/snd_dbopl.cc b/src/sound/snd_dbopl.cc
index 00af31d..2e6baa2 100644
--- a/src/sound/snd_dbopl.cc
+++ b/src/sound/snd_dbopl.cc
@@ -40,6 +40,12 @@
 #include "dbopl.h"
 #include "nukedopl.h"
 #include "snd_dbopl.h"
+#ifdef _MSC_VER
+/* for _alloca() and printing of the related error message with pclog() */
+#include <stdio.h>
+#include <malloc.h>
+#include "../emu.h"
+#endif
 
 
 int opl3_type = 0;
@@ -184,7 +190,17 @@ uint8_t opl_read(int nr, uint16_t addr)
 void opl2_update(int nr, int16_t *buffer, int samples)
 {
         int c;
+#ifdef _MSC_VER
+        /* TODO: Fix this to use a static buffer */
+        if (samples > 512*1024)
+        {
+            pclog("opl2_update: possible stack overflow detected. sample count was %d", samples);
+            return;
+        }
+        Bit32s *buffer_32 = (Bit32s *)_alloca(samples);
+#else
         Bit32s buffer_32[samples];
+#endif
         
         opl[nr].chip.GenerateBlock2(samples, buffer_32);
         
@@ -195,7 +211,17 @@ void opl2_update(int nr, int16_t *buffer, int samples)
 void opl3_update(int nr, int16_t *buffer, int samples)
 {
         int c;
+#ifdef _MSC_VER
+        /* TODO: Fix this to use a static buffer */
+        if (samples > 512 * 1024)
+        {
+            pclog("opl2_update: possible stack overflow detected. sample count was %d", samples);
+            return;
+        }
+        Bit32s *buffer_32 = (Bit32s *)_alloca(samples);
+#else
         Bit32s buffer_32[samples*2];
+#endif
 
 	if (opl3_type)
 	{