header design
Even with the right header design, we still need to consider symbol visibility.
pimpl
Implemented in the form of forward declaration and opaque pointer.
- pimpl hides private symbol
- class struct is not built into client code
- pimpl might require additional memory allocation
Pimpl relies on the fact that imcompleted type can be used as pointer.
abstract interface + factory function
some rule to remember
- You cannot change the order of virtual function declaration
- Compiler might choose to call virtual function directly if it determines it is safe to do so.
check against abi change
mac os
The abi issue is mitigated by -mmacosx-min-version which specify the minimal abi version.
And unsupported feature will trigger a error.
calling convention
Calling conventions describe the interface of called code:
- The order in which atomic (scalar) parameters, or individual parts of a complex parameter, are allocated
- How parameters are passed (pushed on the stack, placed in registers, or a mix of both)
- Which registers the called function must preserve for the caller (also known as: callee-saved registers or non-volatile registers)
- How the task of preparing the stack for, and restoring after, a function call is divided between the caller and the callee
- in c language, the decleration can have less parameters than implementation
- the exceeding amount is not read
known abi problem
_GLIBCXX_USE_CXX11_ABI
anoy namespace c++?