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cmd/compile: type alias error when compiled with assembly file including go_asm.h #22877

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zhaozhiqianghw opened this issue Nov 25, 2017 · 4 comments
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cmd/compile: type alias error when compiled with assembly file including go_asm.h #22877

zhaozhiqianghw opened this issue Nov 25, 2017 · 4 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. release-blocker
Milestone
Go1.10

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@zhaozhiqianghw
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Please answer these questions before submitting your issue. Thanks!

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

Go 1.9.2

Does this issue reproduce with the latest release?

I don't know

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

linux amd64

What did you do?

I have two files, main.go and asm_amd64.s

// main.go
package main

type S struct {
     i int
}

type SS = S

func Sub()

func main() {
     Sub()
}

and

#include "go_asm.h"
#include "textflag.h"

TEXT  ·Sub(SB), NOSPLIT, $0-16
       RET

What did you expect to see?

I use go build -o main, expect a success compiling.

What did you see instead?

# _/home/zhaozq/work/test/go/typealias
go_asm.h:6: redefinition of macro: S__size
make: *** [all] Error 2

The log tells me that the go_asm.h is wrong, so I use go tool compile -o main.o -asmhdr go_asm.h main.go, get go_asm.h as follows:

// generated by compile -asmhdr from package main

#define S__size 8
#define S_i 0
#define S__size 8
#define SS_i 0

Actually, this is a wrong file. So when I remove the statement #include go_asm.h in asm_amd64.s, the compiling is successful. Because this error file doesn't been used.

And I find this file is generated in cmd/compile/internal/gc/export.go:370

func dumpasmhdr() {
      b, err := bio.Create(asmhdr)
      if err != nil {
            Fatalf("%v", err)
      }
      fmt.Fprintf(b, "// generated by compile -asmhdr from package %s\n\n", localpkg.Name)
      for _, n := range asmlist {
            if n.Sym.IsBlank() {
                  continue
            }
            switch n.Op {
            case OLITERAL:
                  fmt.Fprintf(b, "#define const_%s %#v\n", n.Sym.Name, n.Val())

            case OTYPE:
                  t := n.Type
                  if !t.IsStruct() || t.StructType().Map != nil || t.IsFuncArgStruct() {
                        break
                  }
                  fmt.Fprintf(b, "#define %s__size %d\n", t.Sym.Name, int(t.Width))
                  for _, t := range t.Fields().Slice() {
                        if !t.Sym.IsBlank() {
                              fmt.Fprintf(b, "#define %s_%s %d\n", n.Sym.Name, t.Sym.Name, int(t.Offset))
                        }
                  }
            }
      }

      b.Close()
}

The code at cmd/compile/internal/gc/export.go:389 is the error.

 fmt.Fprintf(b, "#define %s__size %d\n", t.Sym.Name, int(t.Width))

Because the Sym t has been change at cmd/compile/internal/gc/typecheck.go:3821

n.Type = p.Ntype.Type

So the code at cmd/compile/internal/gc/export.go:389 should be changed to

 fmt.Fprintf(b, "#define %s__size %d\n", n.Sym.Name, int(t.Width))

When I changed this, the go_asm.h becomes

// generated by compile -asmhdr from package main

#define S__size 8
#define S_i 0
#define SS__size 8
#define SS_i 0

Then the world becomes good.
@bradfitz bradfitz changed the title compile: type alias error when compiled with assembly file including go_asm.h cmd/compile: type alias error when compiled with assembly file including go_asm.h Nov 25, 2017
@bradfitz bradfitz added the NeedsFix The path to resolution is known, but the work has not been done. label Nov 25, 2017
@bradfitz bradfitz added this to the Go1.10 milestone Nov 25, 2017
@bradfitz
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/cc @ianlancetaylor

@ianlancetaylor
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CC @mdempsky

@mdempsky mdempsky self-assigned this Nov 29, 2017
@gopherbot
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Change https://golang.org/cl/80759 mentions this issue: cmd/compile: make -asmhdr work with type aliases

@gopherbot
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Change https://golang.org/cl/118475 mentions this issue: [release-branch.go1.9] cmd/compile: make -asmhdr work with type aliases

gopherbot pushed a commit that referenced this issue Jun 13, 2018
@mdempsky @ianlancetaylor
[release-branch.go1.9] cmd/compile: make -asmhdr work with type aliases
1746cff 
For "type T = U" we were accidentally emitting a #define for "U__size"
instead of "T__size".

Updates #22877.
Fixes #25561.

Change-Id: I5ed6757d697753ed6d944077c16150759f6e1285
Reviewed-on: https://go-review.googlesource.com/80759
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit 2f588ff)
Reviewed-on: https://go-review.googlesource.com/118475
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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