cmd/cgo: cannot call functions with variable-argument lists. #975
Comments
I'm not sure this will ever work. It's very hard to type check and do correctly. Labels changed: added priority-low, removed priority-medium. Owner changed to r...@golang.org. Status changed to LongTerm. |
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I think this should be documented as it is a long-term issue. While wiki says:
The documentation of cgo should be more explicit for the issue, but now it not even mention this. |
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@LionNatsu, please file a new bug just for documenting that. It's true that I see nothing at https://golang.org/cmd/cgo/ about variadic args. |
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Change https://golang.org/cl/90415 mentions this issue: |
The current implementation does not support calling C variadic functions (as discussed in #975). Document that. Fixes #23537 Change-Id: If4c684a3d135f3c2782a720374dc4c07ea66dcbb Reviewed-on: https://go-review.googlesource.com/90415 Reviewed-by: Ian Lance Taylor <iant@golang.org>
The current implementation does not support calling C variadic functions (as discussed in golang#975). Document that. Fixes golang#23537 Change-Id: If4c684a3d135f3c2782a720374dc4c07ea66dcbb Reviewed-on: https://go-review.googlesource.com/90415 Reviewed-by: Ian Lance Taylor <iant@golang.org>
…) that supports only one tag as cgo does not support functions with variable-argument lists (see golang/go#975)
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This would help with @progrium's MacDriver: https://dev.to/progrium/use-mac-apis-and-build-mac-apps-with-go-ap6 /cc @ianlancetaylor |
ianlancetaylor
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NeedsInvestigation
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n order to implement this, we need to be able to rewrite into a call to a generated Go function which means that we need to generate and similarly for a C wrapper function. That is all fine, but in order to write these functions we need to know the types of the Go arguments. Normally we can simply use the types of the C function parameters, which we can get from the C debug info. But of course for a C variadic function we have no type information for the variadic arguments. That means that we need to use the types of the Go arguments. But currently cgo does not know those types. So I think this has to wait for #16623. |
by akidan:
A package such as the following will not compile with cgo. (printf is a contrived example, but this would be useful for bridging objective c through id objc_msgSend(id self, SEL op, ...);) --- (file foo.go) package foo // #include <stdio.h> import "C" func PrintStuff() { C.printf(C.CString("Hello")) } --- $ cgo foo.go What is the expected output? Program compiles and is able to call function with variable-argument list. What do you see instead? unexpected type: ... What is your $GOOS? $GOARCH? darwin amd64 Which revision are you using? (hg identify) 43fd9bb529f0+ tipThe text was updated successfully, but these errors were encountered: