MSP430 IAR C/C++ Compiler reference guide - Rice University

Calling assembler routines from C++●●●The global variablesThe function parametersHow to create space on the stack (auto variables)● Call frame information (CFI).The CFI directives describe the call frame information needed by the Call Stack windowin the IAR C-SPY Debugger.Calling assembler routines from C++The C calling convention does not apply to C++ functions. Most importantly, a functionname is not sufficient to identify a C++ function. The scope and the type of the functionare also required to guarantee type-safe linkage, and to resolve overloading.Another difference is that non-static member functions get an extra, hidden argument,the this pointer.However, when using C linkage, the calling convention conforms to the C callingconvention. An assembler routine may therefore be called from C++ when declared inthe following manner:extern "C"{int my_routine(int x);}Memory access layout of non-PODs (“plain old data structures”) is not defined, and maychange between compiler versions. Therefore, we do not recommend that you accessnon-PODs from assembler routines.To achieve the equivalent to a non-static member function, the implicit this pointer hasto be made explicit:class X;extern "C"{void doit(X *ptr, int arg);}88MSP430 IAR C/C++ CompilerReference Guide