update gencpp to latest and adjsut gen_src.pp accordingly.

codegen/gencpp/AST_Design.md

@@ -0,0 +1,58 @@
+## Navigation
+
+[Top](../Readme.md)
+
+<- [docs - General](Readme.md)
+
+## Current Design
+
+`AST` is the actual managed node object for the library.  
+Its raw and really not meant to be used directly.
+
+All user interaction must be with its pointer so the type they deal with is `AST*`.  
+In order to abstract away constant use of `AST*` its wrapped in a Code type which can be either:
+
+When its the [C generated variant of the library](../gen_c_library/)
+```c
+typedef AST* Code;
+tyepdef AST_<name>* Code<name>;
+...
+```
+
+**or**
+
+For C++:
+```cpp
+struct Code {
+    AST* ast;
+};
+struct Code<name> {
+    ...
+
+    AST_<name>* ast;
+};
+```
+
+The full definitions of all asts are within:
+
+* [`ast.hpp`](../base/components/ast.hpp)
+* [`ast_types.hpp`](../base/components/ast_types.hpp)
+* [`code_types.hpp`](../base/components/code_types.hpp)
+
+The C/C++ interface procedures are located with `ast.hpp` (for the Code type), and `code_types.hpp` for all others.
+
+## Serialization
+
+All code types can either serialize using a function of the pattern:
+
+```c
+StrBuilder <prefix>_to_string(Code code);
+// or
+<prefix>_to_string(Code code, StrBuilder& result);
+```
+
+Where the first generates strings allocated using Allocator_StringArena and the other appends an existing strings with their backed allocator.
+
+Serialization of for the AST is defined for `Code` in [`ast.chpp`](../base/components/ast.cpp) with `code_to_strbuilder_ptr` & `code_to_string`.  
+Serializtion for the rest of the code types is within [`code_serialization.cpp`](../base/components/code_serialization.cpp).  
+Gencpp's serialization does not provide coherent formatting of the code. The user should use a formatter after serializing.