I have a project in pure C - st usb library and I need to migrate it to c++ and change same structures into classes. I removed all c++ "protections" like:
#ifdef __cplusplus
extern "C" {
#endif
#ifdef __cplusplus
}
#endif
I changed all files extensions from .c to .cpp (except HAL library).
I realized that c++ .hex is 7kB smaller then c .hex. When I looked into .map file I saw that many functions are missing. I thought that staticfunctions caused that, but removing static key word didn't help. Does anyone have idea what could cause that some functions weren't compiled. When extensions are .c everything is fine.
C++ functions are given different signatures than C functions. Since you lost functionality and the code is much smaller, it's likely that a function that requires C linkage is being compiled as C++ and the signature mismatch is preventing proper linking.
A likely place for this to happen is in the interrupt vector table. If the handler function is compiled with C++ linkage, the handler address won't make it into a table that's compiled with C.
Double check the interrupt vectors and make sure that they reference the correct functions. If they are correct, check any other code compiled with C that might reference an external symbol compiled with C++.