Just docs, so maybe we can sneak it into 1.8 yet.

We tried giving a warning if the -X variable did not exist in the program, but that broke people that use -X all the time but for whom only some programs have the variable in question. That seemed like a reasonable workflow, so we decided that we shouldn't break it.

The problem with your program is that you are using a const. The docs say you must use a "string variable". A const is not a "string variable".

I'm not sure where to put an example. cmd/link/doc.go seems like an odd place for that, as there are no other examples there. Do you have any suggestions?

if you read my comment right above that I tried var version string to the same result.

Not sure of a better place to put it. maybe an example .go file with a link from the cmd/link/doc?

Would a change like https://golang.org/cl/34230 help?

CL https://golang.org/cl/34230 mentions this issue.

yes, super helpful actually.

but it also brings up more questions, I'll play with it more tomorrow and make sure what I'm seeing actually works as I expect. but otherwise it looks good.

CL is incorrect and should be reverted.

Oh? It worked for my initial tests.

CL https://golang.org/cl/34791 mentions this issue.

@james-lawrence It sounds like the part missing from the docs that would have helped you is that package main's import path is 'main', not the fully-qualified directory name like for other packages. Am I right that that's what you needed? Or do I misunderstand your situation above?

Thanks.

@ianlancetaylor, now that the docs have been reverted, do you want to say something else there instead?

The sentence I can imagine adding would be something like

The importpath for the top-level package main is "main".

But I'm a little confused because in @james-lawrence's original post explicitly calls out that the examples he found use 'main', so I was expecting a different shortcoming in the docs.

@rsc it was both the main package piece. (In retrospect thats fairly obvious and i just missed it) and the types for which it works. I was having issues in regular packages as well, not main ones. i was also surprised by no support for const :)

My initial use cases for using this included both main package and any random package.

They were:

• compile time optimizing of code. Ie set a bool const to false to optimize a code path out. (Build flags are more suited to this in retrospect)
• setting a version value at build.

I've added an example of using -X to https://golang.org/wiki/GcToolchainTricks .

That's the best approach I've been able to come up with. I'm not sure it's worth adding a pointer from the cmd/link page; I hope that search engines will give the Go wiki high relevance as they discover it. I'm going to close this issue.