From 55c2efa3ea6d9bb17b9a14344fa823779b093f7d Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Tue, 27 Sep 2022 05:32:13 -0700
Subject: [PATCH] GB: Don't try to map a 0-byte SRAM (fixes #2668)

---
 CHANGES     |  1 +
 src/gb/gb.c | 16 +++++++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/CHANGES b/CHANGES
index 442380f5d..c374c18fc 100644
--- a/CHANGES
+++ b/CHANGES
@@ -63,6 +63,7 @@ Other fixes:
  - FFmpeg: Fix GIF recording (fixes mgba.io/i/2393)
  - GB: Fix temporary saves
  - GB: Fix replacing the ROM crashing when accessing ROM base
+ - GB: Don't try to map a 0-byte SRAM (fixes mgba.io/i/2668)
  - GB, GBA: Save writeback-pending masked saves on unload (fixes mgba.io/i/2396)
  - mGUI: Fix FPS counter after closing menu
  - Qt: Fix some hangs when using the debugger console
diff --git a/src/gb/gb.c b/src/gb/gb.c
index 3f9fd59a6..dc3a37191 100644
--- a/src/gb/gb.c
+++ b/src/gb/gb.c
@@ -276,13 +276,17 @@ void GBResizeSram(struct GB* gb, size_t size) {
 					vf->seek(vf, size, SEEK_SET);
 					vf->write(vf, extdataBuffer, vfSize & 0xFF);
 				}
-				gb->memory.sram = vf->map(vf, size, MAP_WRITE);
-				memset(&gb->memory.sram[vfSize], 0xFF, size - vfSize);
+				if (size) {
+					gb->memory.sram = vf->map(vf, size, MAP_WRITE);
+					memset(&gb->memory.sram[vfSize], 0xFF, size - vfSize);
+				}
 			} else if (size > gb->sramSize || !gb->memory.sram) {
 				if (gb->memory.sram) {
 					vf->unmap(vf, gb->memory.sram, gb->sramSize);
 				}
-				gb->memory.sram = vf->map(vf, size, MAP_WRITE);
+				if (size) {
+					gb->memory.sram = vf->map(vf, size, MAP_WRITE);
+				}
 			}
 		} else {
 			if (gb->memory.sram) {
@@ -296,9 +300,11 @@ void GBResizeSram(struct GB* gb, size_t size) {
 				gb->sramVf = newVf;
 				vf->truncate(vf, size);
 			}
-			gb->memory.sram = vf->map(vf, size, MAP_READ);
+			if (size) {
+				gb->memory.sram = vf->map(vf, size, MAP_READ);
+			}
 		}
-		if (gb->memory.sram == (void*) -1) {
+		if (!size || gb->memory.sram == (void*) -1) {
 			gb->memory.sram = NULL;
 		}
 	} else if (size) {