[cfe-dev] [FileCheck] RFC: Add support for line anchors.

[Joel E. Denny via cfe-dev]

On Fri, Jul 17, 2020 at 2:52 PM Joel E. Denny <jdenny.ornl at gmail.com> wrote:

> Hi Nathan,
>
> On Fri, Jul 17, 2020 at 12:23 PM Nathan James via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Hello,
>>
>> I was wondering about extending FileCheck to enable creating line
>> anchors. These are numeric variables that hold the value of the line
>> number that where they were defined.
>>
>
> I think something like this could be useful.  However, I think it would be
> more useful to have a general directive for defining FileCheck variables
> inline without trying to capture from input.  For example:
>
> ```
> #define BAD_FUNCTION() badFunction() // CHECK-DEFINE: [[#BAD_FUNC:@LINE]]
> // Further down in the file
>   BAD_FUNCTION();
> CHECK-NOTES: [[@LINE-1]]:3: warning: called a bad function
> CHECK-NOTES :[[#BAD_FUNC]]:3: note: expanded from macro 'BAD_FUNCTION'
> ```
>
> The exact syntax is debatable.
>
> I think this form is more useful because it can also define strings or
> numerics (or maybe even patterns) to be reused in multiple FileCheck
> directives across multiple FileCheck calls from different RUN lines.
> Currently, you either have to capture such a variable from the input or
> specify it with -D on every FileCheck call that needs it.
>
> James Henderson: Weren't you working on something like this?
>
> Thanks.
>
> Joel
>
>
>>
>> The motivation for this comes from test cases using clang-based
>> diagnostics which often include notes attached to source locations in
>> different parts of the file. In order to test for the correct location
>> of the note, the line number has to be written explicitly or as an,
>> often large, offset to the current line. This harms both readability
>> and maintainability. Using this new system one could append a line of
>> interest with an anchor-comment and refer back to it inside FileCheck.
>>
>
Also, just in case you weren't aware, there is a Clang facility for
checking its own diagnostics:

http://clang.llvm.org/doxygen/classclang_1_1VerifyDiagnosticConsumer.html#details

You'd put a directive for each diagnostic on or near the line it cites.

Joel


>
>> I have created a basic patch that implements this here
>> https://reviews.llvm.org/D84037 but it definitely needs a few looks
>> over by people who are more clued up on the internal of FileCheck.
>>
>> The current syntax, based off this patch, is as follows:
>>   - Added a command line option called `anchor-prefix` which is a
>> comma-seperated list of prefixes to be used when declaring anchors.
>> This is defaulted to `LINE-ANCHOR`
>>   - To declare a anchor in the test file use
>>     `LINE-ANCHOR: ANCHOR_NAME`
>>     note: If you specify a different anchor-prefix using the command
>> line, use that name instead of `LINE-ANCHOR`
>>     ANCHOR_NAME Follows the rules all other variable names aside from
>> the fact it can't start with '$'.
>>   - When referring to an anchor in a check use the same numeric
>> variable syntax that FileCheck already supports:
>>     `CHECK: [[#ANCHOR_NAME]][[#ANCHOR_NAME+1]]`
>>
>> Here is a brief (contrived) example of the usage of this:
>> ```
>> #define BAD_FUNCTION() badFunction() // LINE-ANCHOR: BAD_FUNC
>> // Further down in the file
>>   BAD_FUNCTION();
>> CHECK-NOTES: [[@LINE-1]]:3: warning: called a bad function
>> CHECK-NOTES :[[#BAD-FUNC]]:3: note: expanded from macro 'BAD_FUNCTION'
>> ```
>>
>> Regards,
>> Nathan James
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>
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