<div dir="ltr"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Jul 17, 2020 at 4:23 PM Nathan James <<a href="mailto:n.james93@hotmail.co.uk">n.james93@hotmail.co.uk</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Joel,<br>
<br>
That sounds like a very nice idea and definitely a direction I could<br>
get behind. However I feel that outside the use case I suggested, this<br>
functionality would only be used to compress CHECK lines that contain<br>
repeated text, not saying its a bad or good thing though. WDYT?<br></blockquote><div><br></div><div>I can think of a few use cases:<br></div><div><br></div><div>1. Capturing `@LINE`, as you suggest.<br></div><div>2. Making a single directive's complex pattern more readable by extracting and naming components.<br></div><div>3. Avoiding the maintenance burden of repeating the same string, numeric, or pattern expression multiple times within a single directive or across multiple directives.</div><div><br></div><div>`-D` can sometimes help with #2 and #3. However, it still has to be repeated across multiple RUN lines in some cases. Moreover, it's sometimes better to define variables near their uses, but the RUN lines can be far away.<br></div><div><br></div><div>As an example of #2 and #3, I've occasionally written subtle patterns, such as `{{$[[:space:]]}}` for newline, that I wanted to use in multiple places. It's not immediately obvious what that pattern does, but `[[NL]]` would be much clearer and could be documented once at its definition.<br></div><div><br></div><div>It just occurred to me that the new directive might require a "CHECK-DEF-CONST" form that is processed before all other directives. Otherwise, forward-references wouldn't be possible. You might want forward-references for #1, for example.<br></div><div></div><div><br></div><div>Joel<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
~Nathan<br>
<br>
On Fri, 2020-07-17 at 14:52 -0400, Joel E. Denny via cfe-dev wrote:<br>
> Hi Nathan,<br>
> <br>
> On Fri, Jul 17, 2020 at 12:23 PM Nathan James via cfe-dev <<br>
> <a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>> wrote:<br>
> > Hello,<br>
> > <br>
> > I was wondering about extending FileCheck to enable creating line<br>
> > anchors. These are numeric variables that hold the value of the<br>
> > line<br>
> > number that where they were defined.<br>
> <br>
> I think something like this could be useful. However, I think it<br>
> would be more useful to have a general directive for defining<br>
> FileCheck variables inline without trying to capture from input. For<br>
> example:<br>
> <br>
> ```<br>
> #define BAD_FUNCTION() badFunction() // CHECK-DEFINE:<br>
> [[#BAD_FUNC:@LINE]]<br>
> // Further down in the file<br>
> BAD_FUNCTION();<br>
> CHECK-NOTES: [[@LINE-1]]:3: warning: called a bad function<br>
> CHECK-NOTES :[[#BAD_FUNC]]:3: note: expanded from macro<br>
> 'BAD_FUNCTION'<br>
> ```<br>
> <br>
> The exact syntax is debatable.<br>
> <br>
> I think this form is more useful because it can also define strings<br>
> or numerics (or maybe even patterns) to be reused in multiple<br>
> FileCheck directives across multiple FileCheck calls from different<br>
> RUN lines. Currently, you either have to capture such a variable<br>
> from the input or specify it with -D on every FileCheck call that<br>
> needs it.<br>
> <br>
> James Henderson: Weren't you working on something like this?<br>
> <br>
> Thanks.<br>
> <br>
> Joel<br>
> <br>
> > The motivation for this comes from test cases using clang-based<br>
> > diagnostics which often include notes attached to source locations<br>
> > in<br>
> > different parts of the file. In order to test for the correct<br>
> > location<br>
> > of the note, the line number has to be written explicitly or as an,<br>
> > often large, offset to the current line. This harms both<br>
> > readability<br>
> > and maintainability. Using this new system one could append a line<br>
> > of<br>
> > interest with an anchor-comment and refer back to it inside<br>
> > FileCheck.<br>
> > <br>
> > I have created a basic patch that implements this here <br>
> > <a href="https://reviews.llvm.org/D84037" rel="noreferrer" target="_blank">https://reviews.llvm.org/D84037</a> but it definitely needs a few looks<br>
> > over by people who are more clued up on the internal of FileCheck.<br>
> > <br>
> > The current syntax, based off this patch, is as follows:<br>
> > - Added a command line option called `anchor-prefix` which is a<br>
> > comma-seperated list of prefixes to be used when declaring anchors.<br>
> > This is defaulted to `LINE-ANCHOR`<br>
> > - To declare a anchor in the test file use<br>
> > `LINE-ANCHOR: ANCHOR_NAME`<br>
> > note: If you specify a different anchor-prefix using the<br>
> > command<br>
> > line, use that name instead of `LINE-ANCHOR`<br>
> > ANCHOR_NAME Follows the rules all other variable names aside<br>
> > from<br>
> > the fact it can't start with '$'.<br>
> > - When referring to an anchor in a check use the same numeric<br>
> > variable syntax that FileCheck already supports:<br>
> > `CHECK: [[#ANCHOR_NAME]][[#ANCHOR_NAME+1]]`<br>
> > <br>
> > Here is a brief (contrived) example of the usage of this:<br>
> > ```<br>
> > #define BAD_FUNCTION() badFunction() // LINE-ANCHOR: BAD_FUNC<br>
> > // Further down in the file<br>
> > BAD_FUNCTION();<br>
> > CHECK-NOTES: [[@LINE-1]]:3: warning: called a bad function<br>
> > CHECK-NOTES :[[#BAD-FUNC]]:3: note: expanded from macro<br>
> > 'BAD_FUNCTION'<br>
> > ```<br>
> > <br>
> > Regards,<br>
> > Nathan James<br>
> > <br>
> > <br>
> > _______________________________________________<br>
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</blockquote></div></div>