I've not gone through the entire patch, but if the problem is merely
the fact that one cannot convert a void* to anything in C++, why not
use a static_cast in syncevolution wherever the struct is used?
Best
Rohan Garg
On Sun, Feb 5, 2012 at 4:27 PM, Patrick Ohly <patrick.ohly@xxxxxxxxx> wrote:
> 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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