Code replacement tool to generate code

Hello, I'm using the code replacement library tool to replace some C code for various functions such as a sum. In the crtool settings for a given function, in the "build information" part, I filled in the "implementation source file" and "implementation header file" fields with the names of the files to be used. The problem is that when I enter the name of the .c file in the "implementation source file" field and then generate the simulink model code, the .c file is not called. While, if I insert the path of the .c file in the "implementation source file" field of the crtool, the model code is generated correctly by recalling the file.

This problem does not occur for the header file.

Why doesn't the "implementation source file" field of the crtool work if I just enter the name of the .c file?

Thank you!