reflect

func Call ¶

func Call(stackArgsType *abi.Type, fn, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs)

Call calls fn with arguments described by stackArgs, stackArgsSize, frameSize, and regArgs.

Arguments passed on the stack and space for return values passed on the stack must be laid out at the space pointed to by stackArgs (with total length stackArgsSize) according to the ABI.

stackRetOffset must be some value <= stackArgsSize that indicates the offset within stackArgs where the return value space begins.

frameSize is the total size of the argument frame at stackArgs and must therefore be >= stackArgsSize. It must include additional space for spilling register arguments for stack growth and preemption.

TODO(mknyszek): Once we don't need the additional spill space, remove frameSize, since frameSize will be redundant with stackArgsSize.

Arguments passed in registers must be laid out in regArgs according to the ABI. regArgs will hold any return values passed in registers after the call.

Call copies stack arguments from stackArgs to the goroutine stack, and then copies back stackArgsSize-stackRetOffset bytes back to the return space in stackArgs once fn has completed. It also "unspills" argument registers from regArgs before calling fn, and spills them back into regArgs immediately following the call to fn. If there are results being returned on the stack, the caller should pass the argument frame type as stackArgsType so that reflectcall can execute appropriate write barriers during the copy.

Call expects regArgs.ReturnIsPtr to be populated indicating which registers on the return path will contain Go pointers. It will then store these pointers in regArgs.Ptrs such that they are visible to the GC.

Arguments passed through to reflectcall do not escape. The type is used only in a very limited callee of reflectcall, the stackArgs are copied, and regArgs is only used in the reflectcall frame.