code review 126990043: cmd/cgo: iterate over names in deterministic order

cmd/cgo: iterate over names in deterministic order

This makes GCC behavior (and cgo build failures) deterministic.

Fixes issue 8487.

Ran this shell command on linux/amd64 (Ubuntu 12.04) before and
after this change:

    for x in `seq 100`; do
      go tool cgo -debug-gcc=true issue8441.go 2>&1 | md5sum
    done | sort | uniq -c

Before:
    67 2cdcb8c7c4e290f7d9009abc581b83dd  -
    10 9a55390df94f7cec6d810f3e20590789  -
    10 acfad22140d43d9b9517bbc5dfc3c0df  -
    13 c337f8fee2304b3a8e3158a4362d8698  -

After:
    100 785c316cbcbcd50896695050e2fa23c1  -

[mdempsky, 2014-08-10 01:33:12]

Hello golang-codereviews@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[bradfitz, 2014-08-10 17:43:09]

R=iant



On Sat, Aug 9, 2014 at 6:33 PM, mdempsky via golang-codereviews <
golang-codereviews@googlegroups.com> wrote:

> Reviewers: golang-codereviews,
>
> Message:
> Hello golang-codereviews@googlegroups.com,
>
> I'd like you to review this change to
> https://code.google.com/p/go
>
>
> Description:
> cmd/cgo: sort names before feeding to GCC
>
> This makes GCC behavior (and cgo build failures) deterministic.
>
> Fixes issue 8487.
>
> Ran this shell command on linux/amd64 (Ubuntu 12.04) without and
> without this change:
>
>     for x in `seq 100`; do
>       go tool cgo -debug-gcc=true issue8441.go 2>&1 | md5sum
>     done | sort | uniq -c
>
> Before:
>     67 2cdcb8c7c4e290f7d9009abc581b83dd  -
>     10 9a55390df94f7cec6d810f3e20590789  -
>     10 acfad22140d43d9b9517bbc5dfc3c0df  -
>     13 c337f8fee2304b3a8e3158a4362d8698  -
>
> After:
>     100 785c316cbcbcd50896695050e2fa23c1  -
>
> Please review this at https://codereview.appspot.com/126990043/
>
> Affected files (+2, -1 lines):
>   M src/cmd/cgo/gcc.go
>
>
> Index: src/cmd/cgo/gcc.go
> ===================================================================
> --- a/src/cmd/cgo/gcc.go
> +++ b/src/cmd/cgo/gcc.go
> @@ -229,7 +229,8 @@
>         // Determine kinds for names we already know about,
>         // like #defines or 'struct foo', before bothering with gcc.
>         var names, needType []*Name
> -       for _, n := range f.Name {
> +       for _, key := range nameKeys(f.Name) {
> +               n := f.Name[key]
>                 // If we've already found this name as a #define
>                 // and we can translate it as a constant value, do so.
>                 if n.Define != "" {
>
>
> --
> You received this message because you are subscribed to the Google Groups
> "golang-codereviews" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to golang-codereviews+unsubscribe@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>

[minux, 2014-08-11 07:34:47]

LGTM.

[iant, 2014-08-11 23:44:31]

LGTM

[iant, 2014-08-11 23:49:43]

*** Submitted as https://code.google.com/p/go/source/detail?r=d37e1b0c2c65 ***

cmd/cgo: iterate over names in deterministic order

This makes GCC behavior (and cgo build failures) deterministic.

Fixes issue 8487.

Ran this shell command on linux/amd64 (Ubuntu 12.04) before and
after this change:

    for x in `seq 100`; do
      go tool cgo -debug-gcc=true issue8441.go 2>&1 | md5sum
    done | sort | uniq -c

Before:
    67 2cdcb8c7c4e290f7d9009abc581b83dd  -
    10 9a55390df94f7cec6d810f3e20590789  -
    10 acfad22140d43d9b9517bbc5dfc3c0df  -
    13 c337f8fee2304b3a8e3158a4362d8698  -

After:
    100 785c316cbcbcd50896695050e2fa23c1  -

LGTM=minux, iant
R=golang-codereviews, bradfitz, minux, iant
CC=golang-codereviews
https://codereview.appspot.com/126990043

Committer: Ian Lance Taylor <iant@golang.org>