santigimeno / node-ioctl Goto Github PK

Whenever I try to read the fb_fix_screeninfo, node.js crashes and says malloc(): memory corruption. My fb_fix_screeninfo structure looks like:

    StructType({
		id: ArrayType(ref.types.char,16),
		smem_start: ref.types.ulong,
		
		smem_len: ref.types.uint,
		type: ref.types.uint,
		type_aux: ref.types.uint,
		visual: ref.types.uint,
		xpanstep: ref.types.ushort,
		ypanstep: ref.types.ushort,
		line_length: ref.types.uint,
		mmio_start: ref.types.ulong,
		
		mmio_len: ref.types.uint,
		accel: ref.types.uint,
		capabilities: ref.types.ushort,
		reserved: ArrayType(ref.types.ushort,2)
	})

I am using this node-ioctl module on a FreeBSD 64-bit operating system. When using an ioctl with a request value that has the top bit set (i.e. 0x8nnnnnnn), an 'ioctl sign-extension ioctl' warning is emitted from the kernel.

This is due to the request value passed from the node side being assigned to an int data type before being passed to the ioctl. On FreeBSD the request data type is an unsigned long , so sign extension occurs. I appreciate there is some complication here as the datatype of request is int in Linux and unsigned long in FreeBSD.

I would suggest changing the line:
int request = args[1]->Uint32Value();
to
unsigned int request = args[1]->Uint32Value();

though I'm not sure if this would cause compilation issues on Linux?

Currently the ioctl return value is directly passed node land. This makes usage very hard to debug when a seemingly random negative integer is returned. This could be avoided by using strerror(errno) on errors.

http://stackoverflow.com/questions/5525795/does-javascript-guarantee-object-property-order

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