[GitHub] [incubator-nuttx] patacongo commented on issue #769: misc/Kconfig: enable LIBC_IOCTL_VARIADIC by default

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patacongo commented on issue #769: misc/Kconfig: enable LIBC_IOCTL_VARIADIC by default
URL: https://github.com/apache/incubator-nuttx/pull/769#issuecomment-612629522
 
 
   This must be a new addition to the specs at OpenGroup.org.  They did not specify ioctl at all in the past.
   
   NOTE: That this is only a thin layer.  It still only accepts one 'unsigned int' argument.  But the ioctl layer just gets that using va_arg. See libs/libc/misc/lib_ioctl.c:
   
       108   va_start(ap, req);
       109   arg = va_arg(ap, unsigned long);
       110   va_end(ap);
       111
       112   /* Then let fs_ioctl() to the real work */
       113
       114   return fs_ioctl(fd, req, arg);
   
   It would take a lot of work to use this properly.  And variadic functions cannot be used in syscalls so we would probably have to have a vioctl().
   
   

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