hi,

I'm doing a D binding myself to <linux/spi/spidev.h>, and has some problems to wrap the C macros.

```
import core.sys.posix.sys.ioctl;

...

/* IOCTL commands */

enum SPI_IOC_MAGIC = 'k';

/**
 *  Orginal C macros.
 *
 * #define SPI_MSGSIZE(N) \
	((((N)*(sizeof (struct spi_ioc_transfer))) < (1 << _IOC_SIZEBITS)) \
		? ((N)*(sizeof (struct spi_ioc_transfer))) : 0)
 */
extern (D) size_t SPI_MSGSIZE(size_t N)
{
    return ((N * (spi_ioc_transfer.sizeof)) < (1 << _IOC_SIZEBITS)) ? (N * (spi_ioc_transfer.sizeof)) : 0;
}

/* #define SPI_IOC_MESSAGE(N) _IOW(SPI_IOC_MAGIC, 0, char[SPI_MSGSIZE(N)]) */
extern (D) auto SPI_IOC_MESSAGE(size_t N)
{
    size_t n = SPI_MSGSIZE(N);
    return _IOW!(char[static n])(SPI_IOC_MAGIC, 0);
    //mixin("return _IOW!(char[n])(SPI_IOC_MAGIC, 0);");
}
```

as shown in the above code, the SPI_IOC_MESSAGE C macro has a param `char[SPI_MSGSIZE(N)]`, what should it be wrapped to the D world?

as you can see, I tried to use the type of `char[static n]` or `char[n]`, and the compile failed:

```
source/spidev.d-mixin-129(129,19): Error: expression expected, not static
source/spidev.d-mixin-129(129,26): Error: found n when expecting ]
source/spidev.d-mixin-129(129,27): Error: found ] when expecting ) following template argument list
source/spidev.d-mixin-129(129,28): Error: found ) when expecting ; following return statement
```

or when removed static,

```
source/spidev.d-mixin-129(129,8): Error: variable n cannot be read at compile time
```

Can anyone help me? Thanks!

On Thursday, 29 March 2018 at 08:47:50 UTC, dangbinghoo wrote:
> hi,
>
> I'm doing a D binding myself to <linux/spi/spidev.h>, and has some problems to wrap the C macros.
>
> [...]

PS: if I just _IOW!(char[])... it compiles, but does it mean it's unsafe? thanks!

On Thursday, 29 March 2018 at 08:47:50 UTC, dangbinghoo wrote:

>  * #define SPI_MSGSIZE(N) \
> 	((((N)*(sizeof (struct spi_ioc_transfer))) < (1 << _IOC_SIZEBITS)) \
> 		? ((N)*(sizeof (struct spi_ioc_transfer))) : 0)
>  */
> extern (D) size_t SPI_MSGSIZE(size_t N)
> {
>     return ((N * (spi_ioc_transfer.sizeof)) < (1 << _IOC_SIZEBITS)) ? (N * (spi_ioc_transfer.sizeof)) : 0;
> }
>
> /* #define SPI_IOC_MESSAGE(N) _IOW(SPI_IOC_MAGIC, 0, char[SPI_MSGSIZE(N)]) */
> extern (D) auto SPI_IOC_MESSAGE(size_t N)
> {
>     size_t n = SPI_MSGSIZE(N);
>     return _IOW!(char[static n])(SPI_IOC_MAGIC, 0);
>     //mixin("return _IOW!(char[n])(SPI_IOC_MAGIC, 0);");
> }
> ```
>

try

> extern (D) auto SPI_IOC_MESSAGE(size_t N)()
> {
>     enum n = SPI_MSGSIZE(N);
>     return _IOW!(char[n])(SPI_IOC_MAGIC, 0);
>     //mixin("return _IOW!(char[n])(SPI_IOC_MAGIC, 0);");
> }

On Thursday, 29 March 2018 at 09:02:16 UTC, Nicholas Wilson wrote:
> On Thursday, 29 March 2018 at 08:47:50 UTC, dangbinghoo wrote:
>
>>  * #define SPI_MSGSIZE(N) \
>> 	((((N)*(sizeof (struct spi_ioc_transfer))) < (1 << _IOC_SIZEBITS)) \
>> 		? ((N)*(sizeof (struct spi_ioc_transfer))) : 0)
>>  */
>> extern (D) size_t SPI_MSGSIZE(size_t N)
>> {
>>     return ((N * (spi_ioc_transfer.sizeof)) < (1 << _IOC_SIZEBITS)) ? (N * (spi_ioc_transfer.sizeof)) : 0;
>> }
>>
>> /* #define SPI_IOC_MESSAGE(N) _IOW(SPI_IOC_MAGIC, 0, char[SPI_MSGSIZE(N)]) */
>> extern (D) auto SPI_IOC_MESSAGE(size_t N)
>> {
>>     size_t n = SPI_MSGSIZE(N);
>>     return _IOW!(char[static n])(SPI_IOC_MAGIC, 0);
>>     //mixin("return _IOW!(char[n])(SPI_IOC_MAGIC, 0);");
>> }
>> ```
>>
>
> try
>
>> extern (D) auto SPI_IOC_MESSAGE(size_t N)()
>> {
>>     enum n = SPI_MSGSIZE(N);
>>     return _IOW!(char[n])(SPI_IOC_MAGIC, 0);
>>     //mixin("return _IOW!(char[n])(SPI_IOC_MAGIC, 0);");
>> }

thanks for your reply, but it will also fail, the compiler just gives me :

----
source/spidev.d-mixin-129(129,8): Error: variable n cannot be read at compile time
----

On Thursday, 29 March 2018 at 09:13:27 UTC, dangbinghoo wrote:
> On Thursday, 29 March 2018 at 09:02:16 UTC, Nicholas Wilson wrote:
>> On Thursday, 29 March 2018 at 08:47:50 UTC, dangbinghoo wrote:
>>
>>>[...]
>>
>> try
>>
>>> [...]
>
> thanks for your reply, but it will also fail, the compiler just gives me :
>
> ----
> source/spidev.d-mixin-129(129,8): Error: variable n cannot be read at compile time
> ----

sorry, I just don't notice the `()`.
yeah! it compiles, but can you explain it? thanks!

On Thursday, 29 March 2018 at 09:16:11 UTC, dangbinghoo wrote:
> On Thursday, 29 March 2018 at 09:13:27 UTC, dangbinghoo wrote:
>> On Thursday, 29 March 2018 at 09:02:16 UTC, Nicholas Wilson wrote:
>>> On Thursday, 29 March 2018 at 08:47:50 UTC, dangbinghoo wrote:
>>>
>>>>[...]
>>>
>>> try
>>>
>>>> [...]
>>
>> thanks for your reply, but it will also fail, the compiler just gives me :
>>
>> ----
>> source/spidev.d-mixin-129(129,8): Error: variable n cannot be read at compile time
>> ----
>
> sorry, I just don't notice the `()`.
> yeah! it compiles, but can you explain it? thanks!

just got it! `size_t N` need to be template param.

Thanks for the help!