[LLVMdev] lit: deprecating trailing \ in RUN lines

[Jim Grosbach]

On Dec 10, 2013, at 1:24 PM, Alp Toker <alp at nuanti.com> wrote:

> 
> On 10/12/2013 19:47, Jim Grosbach wrote:
>> 
>> On Dec 10, 2013, at 11:26 AM, Alp Toker <alp at nuanti.com> wrote:
>> 
>>> 
>>> On 10/12/2013 18:03, Jim Grosbach wrote:
>>>>> That causes dissonance between what the compiler sees and what lit.py sees for no particularly good reason. One of the nice properties of lit tests is that they're also valid compiler inputs, so trailing slash is a bit unfortunate.
>>>>> 
>>>> 
>>>> How does the backslash break this in any way?
>>> 
>>> The backslash is interpreted by lit and the compiler in different and incompatible ways.
>> 
>> I disagree that this is different or incompatible.
>> 
>> In any case, you didn’t answer the more important of my two questions. What compilers interpret this code differently?
> 
> Hi Jim,
> 
> There are lots of ways line continuations are interpreted differently between compilers and even different versions from the same vendor.\

> 
> This is inherent because each frontend has a different take on fundamental issues like where lines and comments begin and end, and even the semantics of what translation phases are vary between compilers.
> 

No, they really don’t, modulo bugs. This is standards compliance territory. If the compilers aren’t conformant implementations, I have zero sympathy.

> Here's one quick example of how compilers interpret this code differently:
> 
> $ printf '//\\ \nint x=0;\nint x=0;' > f.c
> 
> $ cat f.c
> //\ 
> int x=0;
> int x=0;
> 
> $ clang -fsyntax-only f.c
> 
> $ gcc-4.9 -fsyntax-only f.c
> 
> $ cl f.c
> Microsoft (R) C/C++ Optimizing Compiler Version 18.00.21005.1 for x64
> Copyright (C) Microsoft Corporation.  All rights reserved.
> 
> f.c(3) : error C2374: 'x' : redefinition; multiple initialization
>         f.c(2) : see declaration of 'x’
That’s a bug in either MSVC or in whatever you’re using to get a bash prompt on windows. Probably line-ending related. It’s incorrectly not recognizing the continuation character at all.

-Jim
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