On Mon, Sep 19, 2016 at 2:08 PM, Ali Demir <dem...@gmail.com> wrote: > Packing option is explicitly specified for VC++: > > https://msdn.microsoft.com/en-us/library/xh3e3fd0.aspx > > The user needs to make sure whatever they pick (or default) in their project > matches what Go compiler used. So it may help to specify what go compiler is > using.
There is no answer to that question. The Go compiler is not running the C compiler. In general the Go compiler expects fields to be aligned to their size. That is, a four byte field is aligned to a four byte boundary, and an eight byte field is aligned to an eight byte boundary. As I said earlier, the compiler emits padding fields so that everything will work if the C compiler uses a smaller alignment. However, things will fail if the C compiler uses a larger alignment. I'm not aware of any such C compiler, but I guess it wouldn't shock me. Ian > On Mon, Sep 19, 2016 at 10:00 AM, Ian Lance Taylor <i...@golang.org> wrote: >> >> On Mon, Sep 19, 2016 at 8:50 AM, Ali Demir <dem...@gmail.com> wrote: >> > Header file won't have padding / alignment info. That would be a >> > compiler >> > setting on the C side that is using the header. So the programmer needs >> > to >> > setup C compiler in a way that is compatible with the go compiler. How >> > would >> > he know how to set it up? Do we just assume defaults are the same >> > between Go >> > and C? >> >> The cgo tool will generate padding fields as needed to ensure that the >> fields are aligned as expected. >> >> It's true that the cgo tool does assume that it knows the alignment >> requirements of the basic types. These requirements are not normally >> changed by compiler options. The alignment requirements of unusual >> types, such as processor-specific vector types, are not relevant, >> since Go can't represent them and they will therefore never appear in >> the Go/C interface. >> >> Do you have a specific concern, or is this purely abstract? >> >> Ian > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
