coding style question on indentation

coding style question on indentation

[Sathya.Perla]

Hi,
Which of the following styling is preferable when a function invocation spans more than one line:

a) Aligning the next line with the first argument by inserting a few spaces after the tabs - as in:

	dma_unmap_page(&adapter->pdev->dev,
			   dma_unmap_addr(rx_page_info, bus),
			   adapter->big_page_size, DMA_FROM_DEVICE);

Documentation/CodingStyle says "spaces are never used for indentation", but I see
scripts/Lindent inserting spaces after tabs for alignment.

OR

b) Just using tabs without needing to align as above:

	dma_unmap_page(&adapter->pdev->dev,
			dma_unmap_addr(rx_page_info, bus),
			adapter->big_page_size, DMA_FROM_DEVICE);


thanks,
-Sathya

Re: coding style question on indentation

[Ben Hutchings]

On Fri, 2011-07-01 at 04:20 -0700, Sathya.Perla@Emulex.Com wrote:
> Hi,
> Which of the following styling is preferable when a function
> invocation spans more than one line:
> 
> a) Aligning the next line with the first argument by inserting a few
> spaces after the tabs - as in:
> 
> 	dma_unmap_page(&adapter->pdev->dev,
> 			   dma_unmap_addr(rx_page_info, bus),
> 			   adapter->big_page_size, DMA_FROM_DEVICE);

My preference, for what it's worth.

> Documentation/CodingStyle says "spaces are never used for indentation", but I see
> scripts/Lindent inserting spaces after tabs for alignment.

I think that's meant to apply to indentation at the start of a statement
or declaration, not when wrapping.

> OR
> 
> b) Just using tabs without needing to align as above:
> 
> 	dma_unmap_page(&adapter->pdev->dev,
> 			dma_unmap_addr(rx_page_info, bus),
> 			adapter->big_page_size, DMA_FROM_DEVICE);

Popular but ugly in my opinion.

Some people also use a single extra tab to indent after wrapping,
whether or not the line break is within a parenthesised expression or
argument list.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: coding style question on indentation

[Joe Perches]

On Fri, 2011-07-01 at 04:20 -0700, Sathya.Perla@Emulex.Com wrote:
> a) Aligning the next line with the first argument by inserting a few spaces after the tabs - as in:
> 
> 	dma_unmap_page(&adapter->pdev->dev,
> 			   dma_unmap_addr(rx_page_info, bus),
> 			   adapter->big_page_size, DMA_FROM_DEVICE);

My preference as well, but your example may not be correct.

I think this better:

         1         2         3         4         5         6         7         8
12345678901234567890123456789012345678901234567890123456789012345678901234567890

	dma_unmap_page(&adapter->pdev->dev, dma_unmap_addr(rx_page_info, bus),
		       adapter->big_page_size, DMA_FROM_DEVICE);

maximally fill to 80 cols, then wrap with maximal tabs using spaces
if necessary to align args after opening parenthesis.
In this case, 2 tabs, 7 spaces.

It is your code though, do what you think best.

Re: coding style question on indentation

[Chris Friesen]

On 07/01/2011 09:23 AM, Joe Perches wrote:

> I think this better:
>
>           1         2         3         4         5         6         7         8
> 12345678901234567890123456789012345678901234567890123456789012345678901234567890
>
> 	dma_unmap_page(&adapter->pdev->dev, dma_unmap_addr(rx_page_info, bus),
> 		       adapter->big_page_size, DMA_FROM_DEVICE);
>
> maximally fill to 80 cols, then wrap with maximal tabs using spaces
> if necessary to align args after opening parenthesis.
> In this case, 2 tabs, 7 spaces.

I think the most flexible is to use hard tabs to align the continued 
line to the same level of indentation as the parent line, then use 
spaces for "pretty" alignment.  That way, it all lines up regardless of 
how many spaces the viewer has set for the equivalent size of hard tabs.

Chris

-- 
Chris Friesen
Software Developer
GENBAND
chris.friesen@genband.com
www.genband.com

Re: coding style question on indentation

[Joe Perches]

On Tue, 2011-07-05 at 13:54 -0600, Chris Friesen wrote:
> On 07/01/2011 09:23 AM, Joe Perches wrote:
> > I think this better:
> >           1         2         3         4         5         6         7         8
> > 12345678901234567890123456789012345678901234567890123456789012345678901234567890
> > 	dma_unmap_page(&adapter->pdev->dev, dma_unmap_addr(rx_page_info, bus),
> > 		       adapter->big_page_size, DMA_FROM_DEVICE);
> > maximally fill to 80 cols, then wrap with maximal tabs using spaces
> > if necessary to align args after opening parenthesis.
> > In this case, 2 tabs, 7 spaces.
> I think the most flexible is to use hard tabs to align the continued 
> line to the same level of indentation as the parent line, then use 
> spaces for "pretty" alignment.  That way, it all lines up regardless of 
> how many spaces the viewer has set for the equivalent size of hard tabs.

True, but none of the common editing tools do this.

You could produce and publish emacs/vi modes for this
and then teach checkpatch to understand this mode and
not complain about the spacing if it matters that much
to you.