rtpdec_h264: fixed incorrect address-of taken

Using operator & makes it actually the type uint8_t (*)[2], althoug the
pointer value remained the same. The cast then pruned the type - added
checks before the cast if the value given is really ptr to a char type.

Dropped the HEVC hint - now little-endian uint16_t ptr cannot be passed
by mistake.

Author: MartinPulec

src/rtp/rtpdec_h264.c

@@ -271,7 +271,7 @@ decode_hevc_nal_unit(struct video_frame *frame, int *total_length, int pass,
     int fu_length = 0;
     enum hevc_nal_type type = pass == 0
                                   ? process_hevc_nal(nal, frame, data, data_len)
-                                  : HEVC_NALU_HDR_GET_TYPE(&nal);
+                                  : HEVC_NALU_HDR_GET_TYPE(nal);
 
     if (type <= NAL_HEVC_MAX) {
             if (pass == 0) {

src/rtp/rtpdec_h264.h

@@ -90,21 +90,6 @@ struct coded_data;
 struct decode_data_rtsp;
 struct video_desc;
 
-#define H264_NALU_HDR_GET_TYPE(nal) (*(const uint8_t *) (nal) & 0x1F)
-#define H264_NALU_HDR_GET_NRI(nal)  ((*(const uint8_t *) (nal) & 0x60) >> 5)
-
-/// @param nal pointer to **big-endian** NAL header
-#define HEVC_NALU_HDR_GET_TYPE(nal) (*(const uint8_t *) (nal) >> 1)
-#define HEVC_NALU_HDR_GET_LAYER_ID(nal) \
-        ((((const uint8_t *) (nal))[0] & 0x1) << 5 | \
-         ((const uint8_t *) (nal))[1] >> 3)
-#define HEVC_NALU_HDR_GET_TID(nal) \
-         (((const uint8_t *) (nal))[1] & 0x7)
-
-#define NALU_HDR_GET_TYPE(nal, is_hevc) \
-        ((is_hevc) ? HEVC_NALU_HDR_GET_TYPE((nal)) \
-                   : H264_NALU_HDR_GET_TYPE((nal)))
-
 int decode_frame_h2645(struct coded_data *cdata, void *decode_data);
 struct video_frame *get_sps_pps_frame(const struct video_desc *desc,
                                       struct decode_data_rtsp *decode_data);
@@ -117,4 +102,35 @@ int width_height_from_hevc_sps(int *widthOut, int *heightOut,
 }
 #endif
 
+// cast just pointers to character types to avoid mistakes
+#ifndef __cplusplus
+#define RTPDEC_SAFE_CAST(var) \
+        _Generic((var), \
+            char *: ((const uint8_t *) (var)), \
+            unsigned char *: ((const uint8_t *) (var)), \
+            const char *: ((const uint8_t *) (var)), \
+            const unsigned char *: ((const uint8_t *) (var)))
+#else
+template <typename T>
+static inline auto
+RTPDEC_SAFE_CAST(T var)
+{
+        static_assert(sizeof var[0] == 1);
+        return (const uint8_t *) var;
+}
+#endif
+
+#define H264_NALU_HDR_GET_TYPE(nal) (*RTPDEC_SAFE_CAST(nal) & 0x1F)
+#define H264_NALU_HDR_GET_NRI(nal)  ((*RTPDEC_SAFE_CAST(nal) & 0x60) >> 5)
+
+#define HEVC_NALU_HDR_GET_TYPE(nal) (*RTPDEC_SAFE_CAST(nal) >> 1)
+#define HEVC_NALU_HDR_GET_LAYER_ID(nal) \
+        (((RTPDEC_SAFE_CAST(nal))[0] & 0x1) << 5 | \
+         (RTPDEC_SAFE_CAST(nal))[1] >> 3)
+#define HEVC_NALU_HDR_GET_TID(nal) (RTPDEC_SAFE_CAST(nal)[1] & 0x7)
+
+#define NALU_HDR_GET_TYPE(nal, is_hevc) \
+        ((is_hevc) ? HEVC_NALU_HDR_GET_TYPE((nal)) \
+                   : H264_NALU_HDR_GET_TYPE((nal)))
+
 #endif