Error in build step #2 (Make): Make process exited with code 2:

Hello, When I try to build models on RT Box 2 I separate the plant and controller with task scheduling with discretization time for plant is 5e-6 s and for controller is 5e-6 s. Could you explain to me why this error happen? and how is your suggestion to fix this error.

Error in build step #2 (Make): Make process exited with code 2:
Compiling Plant_main.o
Compiling Plant.o
Plant.mk:65: recipe for target ‘Plant.o’ failed

Plant.c: In function ‘Plant_initialize’:
Plant.c:539:26: error: incompatible types when assigning to type ‘float’ from type ‘_attribute_((const)) double (*)(const char *)’
Plant_X_Plant_PM1_x[8] = nan;
^
make: *** [Plant.o] Error 1