cmd/cgo: document cgo [0]byte bug fix #7958
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Comment 1 by miha.dimec@visionect.com: Ups sorry for typing error. I meant cgo namespace in the title. |
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Comment 4 by miha.dimec@visionect.com: This is correct behavior then? |
You are using C.foo types in your exported API. I don't believe this ever worked. Internally C.foo becomes a name like *_C_foo. Those names are different in different packages: you cannot pass a *gdk._C_foo where a *cairo._C_foo is expected. This may have worked in the past because cgo was incorrectly turning all undefined structs into *[0]byte, so that they were all interchangeable. CL https://golang.org/cl/76450043 fixed this. I think the fix is correct and that your original program was incorrect. This issue is now about documenting the [0]byte change in that CL. Status changed to Accepted. |
Maybe http://golang.org/cmd/cgo should also talk about how C.foo names get translated. Currently, it only speaks of a "pseudo-package", which might lead one to believe that all C.foo refer to the same C.foo, no matter in which package they appear. |
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Comment 8 by miha.dimec@visionect.com: Ok thank you. Then corrections need to be made inside library. |
CL https://golang.org/cl/91520043 mentions this issue. |
CL https://golang.org/cl/91590044 mentions this issue. |
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This issue was closed by revision 7ef0eb1. Status changed to Fixed. |
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This issue was closed by revision 3f66c0c. |
wheatman
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Jun 25, 2018
Fixes golang#7958. LGTM=rsc R=golang-codereviews, rsc, r, gobot CC=golang-codereviews https://golang.org/cl/91520043
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by miha.dimec@visionect.com:
What does 'go version' print? go version devel +f8b50ad4cac4 Mon Apr 21 17:00:27 2014 -0700 + linux/amd64 What steps reproduce the problem? Code snippet that does compile under go.1.2.2 but does not under go.1.3 cairo.go: package cairo // #cgo pkg-config: cairo cairo-gobject // #include <stdlib.h> // #include <cairo.h> // #include <cairo-gobject.h> import "C" ... type Context struct { context *C.cairo_t } ... func WrapContext(context *C.cairo_t) *Context { ctx := &Context{context} ctx.reference() return ctx } ... gdk.go: func CairoCreate(window *Window) *cairo.Context { ctx := C.gdk_cairo_create(window.native()) if ctx == nil { return nil } return cairo.WrapContext(ctx) } I am trying to compile a local branch of github.com/confomal/gotk3 library using latest go.1.3 build. What happened? $ go build github.com/visionect/gotk3/gdk # github.com/visionect/gotk3/gdk src/github.com/visionect/gotk3/gdk/gdk.go:287: cannot use ctx (type *C.cairo_t) as type *cairo.C.cairo_t in argument to cairo.WrapContext What should have happened instead? Don't know if this is the correct behavior, but code compiled normally with Go 1.2.2 and older.The text was updated successfully, but these errors were encountered: