The compiler error is:
/usr/include/bluetooth/bluetooth.h::131:9: error: invalid conversion from 'void*' to 'bt_get_le64(void*)::<anonymous struct>*'
...
The reason is that C++, in contrast to C, does not allow conversion of
void * to anything, and this code gets compiled as C++ when the app is
written in C++. The macro with the assignment itself is older, but only
recent Bluez starts to use it in inline functions, thus triggering the
problem.
This patch keeps the "struct __attribute__((packed))" magic and merely
changes the typecast so that it works in C and C++. Like the existing
macro this patch relies on support for typeof.
The new variant of the code is in an ifdef and only used for C++
to avoid unexpected regressions in C applications.
Signed-off-by: Patrick Ohly <patrick.ohly@xxxxxxxxx>
---
lib/bluetooth.h | 30 ++++++++++++++++++++++++++++++
1 files changed, 30 insertions(+), 0 deletions(-)
diff --git a/lib/bluetooth.h b/lib/bluetooth.h
index 5bd4f03..3293915 100644
--- a/lib/bluetooth.h
+++ b/lib/bluetooth.h
@@ -109,6 +109,11 @@ enum {
#endif
/* Bluetooth unaligned access */
+#ifndef __cplusplus
+/*
+ * traditional code, doesn't work in C++ because
+ * of the void * to struct pointer assignment
+ */
#define bt_get_unaligned(ptr) \
({ \
struct __attribute__((packed)) { \
@@ -125,6 +130,31 @@ do { \
__p->__v = (val); \
} while(0)
+#else /* __cplusplus */
+
+/*
+ * modified code with typeof typecast, for C++;
+ * the traditional code continues to be used for
+ * C to avoid unexpected regressions with this
+ * code here (it should work in C and C++, though)
+ */
+#define bt_get_unaligned(ptr) \
+({ \
+ struct __attribute__((packed)) { \
+ typeof(*(ptr)) __v; \
+ } *__p = (typeof(__p)) (ptr); \
+ __p->__v; \
+})
+
+#define bt_put_unaligned(val, ptr) \
+do { \
+ struct __attribute__((packed)) { \
+ typeof(*(ptr)) __v; \
+ } *__p = (typeof(__p)) (ptr); \
+ __p->__v = (val); \
+} while(0)
+#endif /* __cplusplus */
+
#if __BYTE_ORDER == __LITTLE_ENDIAN
static inline uint64_t bt_get_le64(void *ptr)
{
--
1.7.8.3
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