ptp2: make a failed realloc in array_extend() return GP_ERROR_NO_MEMORY

To be able to use the array macros in PTP and GP error "contexts", this
makes translate_ptp_result() tolerate both "types" of errors.

I added a comment regarding the use of the GP_ERROR_NO_MEMORY use. This is
related to gphoto#1008.

camlibs/ptp2/library.c

@@ -133,7 +133,18 @@ translate_ptp_result (uint16_t result)
 	case PTP_ERROR_IO:
 	case PTP_ERROR_DATA_EXPECTED:
 	case PTP_ERROR_RESP_EXPECTED:		return GP_ERROR_IO;
-	default:				return GP_ERROR;
+	default: {
+		/* If result is actually a GP_ERROR code (see gphoto2-port-result.h), then we simply pass it through as is.
+		 * This works because those two value ranges have no overlap:
+		 *   - PTP errors are either 0x0..., 0x2.... or 0xA....
+		 *   - GP errors (as uint16_t) are 0xF...
+		 */
+		int int_res = (int16_t)result;
+		if (-99 <= int_res && int_res <= 0)
+			return int_res;
+		else
+			return GP_ERROR;
+	}
 	}
 }
 

camlibs/ptp2/ptp.h

@@ -31,6 +31,8 @@
 #include <iconv.h>
 #endif
 #include "libgphoto2/gphoto2-endian.h"
+#include <gphoto2/gphoto2-port-log.h>
+#include <gphoto2/gphoto2-port-result.h>
 #include "device-flags.h"
 
 #ifdef __cplusplus
@@ -102,8 +104,10 @@ static inline uint32_t _post_inc(uint32_t* o, int n)
 
 #define array_extend(ARRAY, LEN) do { \
 	(ARRAY)->val = realloc((ARRAY)->val, ((ARRAY)->len + (LEN)) * sizeof((ARRAY)->val[0])); \
-	if (!(ARRAY)->val) \
-		ptp_error(params, "PANIC: realloc failed"); \
+	if (!(ARRAY)->val) { \
+		GP_LOG_E ("Out of memory: 'realloc' of %ld bytes failed.", ((ARRAY)->len + (LEN)) * sizeof((ARRAY)->val[0])); \
+		return GP_ERROR_NO_MEMORY; \
+	} \
 } while(0)
 
 #define array_push_back(ARRAY, VAL) do { \

libgphoto2_port/gphoto2/gphoto2-port-result.h

@@ -40,6 +40,13 @@
  * \brief Out of memory
  */
 #define GP_ERROR_NO_MEMORY		-3
+/* FIXME: GP_ERROR_NO_MEMORY is used to communicate two completely differnt
+ * things, which have nothing to do with each other:
+ *  - the camera went out of memory because the storage space ran out, this
+ *    is totally "normal"
+ *  - a malloc on the host computer failed: this will completely interrupt
+ *    the functionality and likely crash the process soonish
+ */
 /**
  * \brief Error in the camera driver
  */