[LLVMdev] [lld] Handling a whole bunch of readers

[Rui Ueyama]

# is a line comment chracter in YAML so it's valid. That's why I wrote a
simple magic "comment".


On Thu, Oct 10, 2013 at 6:21 PM, Shankar Easwaran
<shankare at codeaurora.org>wrote:

> On 10/10/2013 5:00 PM, Rui Ueyama wrote:
>
>> On Thu, Oct 10, 2013 at 9:16 AM, Shankar Easwaran
>> <shankare at codeaurora.org>**wrote:
>>
>>  On 10/9/2013 11:19 PM, Rui Ueyama wrote:
>>>
>>>  Isnt having a YAML file starting with the below better, so that you dont
>>>> need to go through file extensions.
>>>>
>>>> magic :
>>>> arch:
>>>>
>>>> I guess we will use a fixed file extension anyway (we probaly don't want
>>>> to
>>>> use .txt for YAML object file for example), so what do you think is the
>>>> benefit of depending on special file magic compared to using file
>>>> extension?
>>>>
>>>>
>>>>   I would like to support usecases like this.
>>>>
>>> (a)
>>> $ cat simple.s
>>>           .text
>>>           .global _start
>>>           .type _start, at function
>>> _start:
>>>           callq bar
>>>           ret
>>>
>>> clang simple.s -c- -o- | lld -flavor gnu -target x86_64
>>> --output-filetype=yaml -r - | lld -flavor gnu -target x86_64 -
>>>
>>> Which is certainly not doable because you dont have a file created on the
>>> filesystem.
>>>
>>>  This is an interesting example but I doubt the actual value of doing
>> that,
>> especially because it cannot handle multiple input files. An alternative
>> command line would be
>>
>>    lld -flavor gnu -target x86_64 <(clang simple.s -c- -o- | lld -flavor
>> gnu
>> -target x86_64 --output-filetype=yaml -r -)
>>
>> which could handle multiple inputs, but it works only on bash and may be
>> too tricky.
>>
>> The compiler usually depends on the file extension to distinguish file
>> type, and your file has a non standard file extension, you can explicitly
>> specify the language type by -x*language* option. Adding a similar option
>>
>> to the linker would be an option for us too.
>>
>> Even if we go with a magic, I'd like to make it a simple magic comment,
>> such as "#!obj" at the beginning of a file. A magic string which is valid
>> as a YAML, such as "magic:" is IMO less flexible and should be avoided.
>>
> YAML only allows key-value pairs. #!obj are all invalid characters for
> YAML files.
>
>
>>  PS: This has been snipped from an earlier discussion with Tim.
>>>
>>> (b)
>>>
>>> lld -flavor gnu -target x86_64 input.o --output-filetype=yaml -o
>>> atoms.objtxt (Create a atom file using x86_64 target)
>>> lld -flavor gnu -target hexagon atoms.objtxt (use it with hexagon)
>>>
>>> You can create yaml files from each flavor and pass it to the wrong
>>> flavor, too.
>>>
>>> If we have the magic and arch in the yaml file (or) one entry combined
>>> triple(that combines flavor, operating system and target) this would work
>>> and there is no need to create new types of extensions.
>>>
>>>
>>> Thanks
>>>
>>> Shankar Easwaran
>>>
>>> -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>>> hosted by the Linux Foundation
>>>
>>>
>>>
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted
> by the Linux Foundation
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20131010/4ddaa754/attachment.html>