Limit max cache to 1800MiB for 32bits compiled binaries and to 4GiB for other. Closes #1698.

src/preferences/advancedsettings.h

@@ -170,7 +170,15 @@ private slots:
     const Preferences* const pref = Preferences::instance();
     // Disk write cache
     spin_cache.setMinimum(0);
-    spin_cache.setMaximum(2048);
+    // When build as 32bit binary, set the maximum at less than 2GB to prevent crashes.
+    // These macros may not be available on compilers other than MSVC and GCC
+#if !defined(_M_X64) || !defined(__amd64__)
+    //1800MiB to leave 248MiB room to the rest of program data in RAM
+    spin_cache.setMaximum(1800);
+#else
+    // 4GiB
+    spin_cache.setMaximum(4*1024);
+#endif
     spin_cache.setValue(pref->diskCacheSize());
     updateCacheSpinSuffix(spin_cache.value());
     setRow(DISK_CACHE, tr("Disk write cache size"), &spin_cache);

src/preferences/preferences.cpp

@@ -1098,11 +1098,37 @@ void Preferences::setShutdownqBTWhenDownloadsComplete(bool shutdown) {
 }
 
 uint Preferences::diskCacheSize() const {
-  return value("Preferences/Downloads/DiskWriteCacheSize", 0).toUInt();
+  uint size = value("Preferences/Downloads/DiskWriteCacheSize", 0).toUInt();
+
+  // When build as 32bit binary, set the maximum at less than 2GB to prevent crashes.
+  // These macros may not be available on compilers other than MSVC and GCC
+#if !defined(_M_X64) || !defined(__amd64__)
+  //1800MiB to leave 248MiB room to the rest of program data in RAM
+  if (size > 1800)
+    size = 1800;
+#else
+  // 4GiB
+  if (size > 4*1024)
+    size = 4*1024;
+#endif
+
+  return size;
 }
 
 void Preferences::setDiskCacheSize(uint size) {
-  setValue("Preferences/Downloads/DiskWriteCacheSize", size);
+  uint size0 = size;
+
+#if !defined(_M_X64) || !defined(__amd64__)
+  //1800MiB to leave 248MiB room to the rest of program data in RAM
+  if (size0 > 1800)
+    size0 = 1800;
+#else
+  // 4GiB
+  if (size0 > 4*1024)
+    size0 = 4*1024;
+#endif
+
+  setValue("Preferences/Downloads/DiskWriteCacheSize", size0);
 }
 
 uint Preferences::diskCacheTTL() const {