cmd/compile: export non-integer constants to debug info

[dlsniper]

What version of Go are you using (go version)?

go1.13.4

Does this issue reproduce with the latest release?

I haven't tried with Go 1.14 yet

What operating system and processor architecture are you using (go env)?

windows/amd64

What did you do?

• use the code at https://github.com/dlsniper/democonstdbg
• use the latest Delve version from master
• place a breakpoint on line 23
• evaluate the following expression:

ot == AnotherConst

What did you expect to see?

A boolean result

What did you see instead?

could not find symbol value for AnotherConst

[aarzilli]

Non-integer constants are never exported to debug_info, it doesn't have anything to do with whether they are inlined or not. Also, I'm not sure it's worth the executable bloat costs, since IIRC there was no way to reuse the strings stored in rodata from the debug_info constant entries.

@gopherbot please add label Debugging

[dlsniper]

Thanks for the explanation.

The problem was reported to GoLand by a user that had a similar code like the one above.
It's rather common to run a compare operation like this. For example, I use this to setup conditional breakpoints. Also, not everyone will know ahead of time that one is a constant or not when making the comparison, nor suggesting to change the code would be possible.

I'm not sure if go-delve/delve#1753 is related or not.

[andybons]

@aclements

[kzhui125]

When I debug this code:

https://github.com/adonovan/gopl.io/blob/65c318dde95e3b46a0add461ccf681bd5345b67c/ch1/lissajous/main.go#L69

and hover at the constant variables, the value doesn't appear.

I have to find the definitions what exactly the value is.

[aarzilli]

@kzhui125 that doesn't have anything to do with this issue and should be reported to GoLand.

[kzhui125]

I am using VSCode, I have reported this issue in vscode-go extension. I was told this is upstream issue. @aarzilli

microsoft/vscode-go#3226

[aarzilli]

You're right, I was confusing this with a different issue.

[x-yuri]

I wonder if that's the issue I'm experiencing...

$ git clone https://github.com/docker/compose
$ cd compose
$ dlv debug github.com/docker/compose/v2/cmd -- up
Type 'help' for list of commands.
(dlv) b /home/yuri/go/pkg/mod/github.com/compose-spec/compose-go/v2@v2.0.0-beta.2/cli/options.go:260
Breakpoint 1 set at 0x199cc8e for github.com/compose-spec/compose-go/v2/cli.WithEnvFiles.func1() /home/yuri/go/pkg/mod/github.com/compose-spec/compose-go/v2@v2.0.0-beta.2/cli/options.go:260
(dlv) c
> github.com/compose-spec/compose-go/v2/cli.WithEnvFiles.func1() /home/yuri/go/pkg/mod/github.com/compose-spec/compose-go/v2@v2.0.0-beta.2/cli/options.go:260 (hits goroutine(1):1 total:1) (PC: 0x199cc8e)
   255:         return func(o *ProjectOptions) error {
   256:                 if len(file) > 0 {
   257:                         o.EnvFiles = file
   258:                         return nil
   259:                 }
=> 260:                 if v, ok := os.LookupEnv(consts.ComposeDisableDefaultEnvFile); ok {
   261:                         b, err := strconv.ParseBool(v)
   262:                         if err != nil {
   263:                                 return err
   264:                         }
   265:                         if b {
(dlv) p consts.ComposeDisableDefaultEnvFile
Command failed: could not find symbol value for consts

Are there any workarounds?

[x-yuri]

@aarzilli (I didn't remember the part about non-integer constants when I was posting the message.)

Can you possibly explain why non-integer constants are not exported? C for one doesn't seem to have problems with them.

[aarzilli]

Can you possibly explain why non-integer constants are not exported?

They just aren't.

[aclements]

I've retitled this issue because it's unrelated to inlining. Really this is a feature request for the compiler to include non-integer constants in the debug info. Once we do that, debuggers will be able to access them.