Specify whether one of an S-function's input ports can be overwritten by one of its output ports
void ssSetInputPortOverWritable(SimStruct *S, int_T port, int_T isOverwritable)
Use in mdlInitializeSizes (after ssSetNumInputPorts) to specify whether port is overwritable by one of the S-function's output ports. The Simulink® engine uses this setting as one criterion in determining whether one of the output ports of this S-function can share memory with port. If isOverwritable=1 and the other criteria are satisfied, the engine allocates a common block of memory for the input port and one of the S-function's output ports, thus reducing simulation memory requirements. The default is isOverwritable=0, which means that port cannot share memory with any of the S-function's output ports.
See the S-function sfun_multirate.csfun_multirate.c used in sfcndemo_sfun_multiratesfcndemo_sfun_multirate and the S-function sdotproduct.csdotproduct.c used in sfcndemo_sdotproductsfcndemo_sdotproduct.