[ragel-users] "declared but not used" errors with v7 Go backend

[Damian Gryski]

Yes, I had to change the call to libtoolize to glibtoolize so it picked up
the version installed by brew and not Apple's version.

Next, I needed to pass CXX=g++-8 so it used the gcc installed by brew and
not Apple's version of llvm.

Finally, I needed to also build colm from git and not use the latest
release tarball 0.13.0.6.

Damian

On Sun, Nov 25, 2018 at 5:18 AM Adrian Thurston <thurston at colm.net> wrote:

> Just added the assignment to _ to master.
>
> Thank you for the fix.
>
> Still having problems building master?
>
> On 2018-11-01 10:12, Damian Gryski wrote:
>
> This is with ragel 7.0.0.11 and colm 0.13.0.6.  I was unable to get ragel
> to build from git.
>
> With the example grammar at github.com/dgryski/ragel-examples/regexp1, I
> get the following error:
>
> $ ragel-go sshd.rl
> $ go build
> # github.com/dgryski/ragel-examples/regexp1
> ./sshd.go:11:6: _scanner_trans_cond_spaces declared and not used
> ./sshd.go:12:6: _scanner_trans_offsets declared and not used
> ./sshd.go:13:6: _scanner_trans_lengths declared and not used
> ./sshd.go:14:6: _scanner_cond_keys declared and not used
> ./sshd.go:17:6: _scanner_eof_cond_spaces declared and not used
> ./sshd.go:18:6: _scanner_eof_cond_key_offs declared and not used
> ./sshd.go:19:6: _scanner_eof_cond_key_lens declared and not used
> ./sshd.go:20:6: _scanner_eof_cond_keys declared and not used
> ./sshd.go:21:6: _scanner_nfa_targs declared and not used
> ./sshd.go:22:6: _scanner_nfa_offsets declared and not used
> ./sshd.go:22:6: too many errors
>
> The usual solution to this in autogenerated code is to assign them to `_`,
> the underscore "blank variable".  This satisfies the compiler and the
> entire array will be eliminated as a dead-store if it ends up not being
> used.
>
> Thus, each declaration for variables which may or may not be used will
> look like:
> var _scanner_trans_cond_spaces [] int8  = [] int8  { ... }
> _ = _scanner_trans_cond_space
>
> Note also the first `[] int8` is redundant -- the compiler will infer the
> type from the type of the array on the right hand side of the `=`.
>
> Fixing these issues in the Go template in the src/host-go directory and
> rebuilding fixed these errors (although I had to copy files from the git
> checkout for the template changes to recompile successfully).
>
> Damian
>
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