Pin buffer around potential async operations (#1193)

libs/core/i2c.cpp

@@ -35,7 +35,9 @@ public:
   Buffer readBuffer(int address, int size, bool repeat = false)
   {
     Buffer buf = mkBuffer(NULL, size);
+    registerGCObj(buf);
     int status = this->i2c.read(address << 1, buf->data, size, repeat);
+    unregisterGCObj(buf);
     if (status != ErrorCode::DEVICE_OK) {
       buf = 0;
     }

libs/serial---linux/serial-target.cpp

@@ -190,7 +190,9 @@ Buffer LinuxSerialDevice::readBuffer() {
     pthread_mutex_lock(&lock);
     int sz = bufferedSize();
     auto r = mkBuffer(NULL, sz);
+    registerGCObj(r);
     int sz2 = readBuf(r->data, sz);
+    unegisterGCObj(r);
     if (sz != sz2)
         target_panic(999);
     pthread_mutex_unlock(&lock);

libs/serial/serial-target.h

@@ -51,17 +51,16 @@ class CodalSerialDeviceProxy {
         // n maybe 0 but we still call read to force
         // to initialize rx
         auto buf = mkBuffer(NULL, n);
+        auto res = buf;
+        registerGCObj(buf);
         auto read = ser.read(buf->data, buf->length, SerialMode::ASYNC);
         if (read == DEVICE_SERIAL_IN_USE || read == 0) { // someone else is reading
-            return mkBuffer(NULL, 0);
+            res = mkBuffer(NULL, 0);
+        } else if (buf->length != read) {
+            res = mkBuffer(buf->data, read);
         }
-        if (buf->length != read) {
-            registerGCObj(buf);
-            auto buf2 = mkBuffer(buf->data, read);
-            unregisterGCObj(buf);
-            buf = buf2;
-        }
-        return buf;
+        unregisterGCObj(buf);
+        return res;
     }
 
     void writeBuffer(Buffer buffer) {

libs/storage/storage.cpp

@@ -164,8 +164,10 @@ Buffer readAsBuffer(String filename) {
     if (sz > 0xffff)
         return NULL;
     auto res = mkBuffer(NULL, sz);
+    registerGCObj(res);
     f->seek(0);
     f->read(res->data, res->length);
+    unregisterGCObj(res);
     return res;
 }