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

[Nathan James via llvm-dev]

On Fri, 2020-07-17 at 14:59 -0400, Joel E. Denny via cfe-dev wrote:
> 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
>   
The use case I was mainly thinking of was clang tools, specifically
clang-tidy. There you need to be able to check diagnostics and fix-its
in one file ideally. Right now you can't use the
VerifyDiagnosticConsumer in there and it also won't be able to veryify
fix-its.

~Nathan
> > > 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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