cmd/link: too many error messages when missing func main

[josharian]

With tip:

$ echo "package main" > m.go
$ go build m.go
# command-line-arguments
runtime.main: call to external function main.main
runtime.main: main.main: not defined
runtime.main: undefined: main.main

With 1.4, there were at least only two; the "call to external function" didn't show up. One would be enough, maybe even one that addresses this fairly special situation head on.

Low priority.

[minux]

Do you think that the compiler should refuse to compile a package with the import path (not just package name) without the main func? This will catch the problem even earlier.

[josharian]

I don't know. Maybe, if -complete has been passed. (Although who writes a main function in assembly?) Or perhaps there are crazy, non-obvious uses in the dynamic linking world?

[minux]

Even for c-archive and c-shared build modes, we still require a dummy main.

[josharian]

See also #24809. The goal there, which dovetails with this issue, is to make it easier to diagnose the problem when you forget to have a func main.

[gopherbot]

Change https://golang.org/cl/113955 mentions this issue: cmd/link: fix duplicated "undefined reloc" errors