AP_Logger: check return values from get_log_data

libraries/AP_Logger/AP_Logger_Block.cpp

@@ -279,7 +279,9 @@ int16_t AP_Logger_Block::get_log_data(uint16_t log_num, uint16_t page, uint32_t
     WITH_SEMAPHORE(sem);
     if (offset == 0) {
         uint8_t header[3];
-        get_log_data_raw(log_num, page, 0, 3, header);
+        if (get_log_data_raw(log_num, page, 0, 3, header) == -1) {
+            return -1;
+        }
         adding_fmt_headers = (header[0] != HEAD_BYTE1 || header[1] != HEAD_BYTE2 || header[2] != LOG_FORMAT_MSG);
     }
     uint16_t ret = 0;
@@ -307,7 +309,11 @@ int16_t AP_Logger_Block::get_log_data(uint16_t log_num, uint16_t page, uint32_t
     }
 
     if (len > 0) {
-        ret += get_log_data_raw(log_num, page, offset, len, data);
+        const int16_t bytes = get_log_data_raw(log_num, page, offset, len, data);
+        if (bytes == -1) {
+            return ret == 0 ? -1 : ret;
+        }
+        ret += bytes;
     }
 
     return ret;

libraries/AP_Logger/AP_Logger_Block.h

@@ -23,7 +23,7 @@ public:
     uint16_t find_last_log() override;
     void get_log_boundaries(uint16_t log_num, uint32_t & start_page, uint32_t & end_page) override;
     void get_log_info(uint16_t log_num, uint32_t &size, uint32_t &time_utc) override;
-    int16_t get_log_data(uint16_t log_num, uint16_t page, uint32_t offset, uint16_t len, uint8_t *data) override;
+    int16_t get_log_data(uint16_t log_num, uint16_t page, uint32_t offset, uint16_t len, uint8_t *data) override WARN_IF_UNUSED;
     uint16_t get_num_logs() override;
     uint16_t start_new_log(void) override;
     uint32_t bufferspace_available() override;
@@ -76,7 +76,7 @@ private:
     bool NeedErase(void);
 
     // internal high level functions
-    int16_t get_log_data_raw(uint16_t log_num, uint32_t page, uint32_t offset, uint16_t len, uint8_t *data);
+    int16_t get_log_data_raw(uint16_t log_num, uint32_t page, uint32_t offset, uint16_t len, uint8_t *data) WARN_IF_UNUSED;
     void StartRead(uint32_t PageAdr);
     uint32_t find_last_page(void);
     uint32_t find_last_page_of_log(uint16_t log_number);