cmd/go: go test -c does not apply specified gcflags to all packages

[aarzilli]

Please answer these questions before submitting your issue. Thanks!

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

go version devel +3aeb395 Mon Dec 18 20:24:12 2017 +0000 linux/amd64

What did you do?

This is very similar to #22831, that problem was fixed however if I run go test -gcflags='all=-N -l' with https://github.com/aarzilli/testflags I expect to see all the compile units in the resulting binary have the flags -N and -l applied to them, but one is spared:

 <0><8fc96>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <8fc97>   DW_AT_name        : github.com/aarzilli/testflags
    <8fcb5>   DW_AT_language    : 22    (Go)
    <8fcb6>   DW_AT_stmt_list   : 0x16b8d
    <8fcba>   DW_AT_low_pc      : 0x531650
    <8fcc2>   DW_AT_ranges      : 0x530
    <8fcc6>   DW_AT_comp_dir    : .
    <8fcc8>   DW_AT_producer    : Go cmd/compile devel +3aeb395 Mon Dec 18 20:24:12 2017 +0000

also all functions in that compile unit are assigned to the package github.com/aarzilli/testflags when really they were defined in main.

[aarzilli]

I looked a bit into this, it turns out that the flags are actually applied to all packages, the reason they are not reported in debug_info is because the compiler for testflags is called with -p main which means the producer symbol is called go.cuinfo.producer.main, but then the linker imports it as github.com/aarzilli/testflags which means the linker will look for go.cuinfo.producer.github.com/aarzilli/testflags.

This part:

all functions in that compile unit are assigned to the package github.com/aarzilli/testflags when really they were defined in main.

isn't new to 1.10, 1.9 also did this.

[rsc]

Thanks for chasing this down. CL sent to fix the -p option in this case.

[gopherbot]

Change https://golang.org/cl/86235 mentions this issue: cmd/go: fix compile -p flag for building test of main package