I'm changing the compiler of a medium-sized codebase, mostly Ada (with some C & C++ modules), from ObjectAda (PTC) to Gnat.

The product consists of ~100 Windows executables and ~20 dlls (~1500 Ada packages + ~20 C & 5 C++ compilation units)

The sources files are anized by "components", in the following way:

• a top folder contains packages shared by almost all components (tools)
• sources of each components are gathered under a top folder per component

Packages in component A don't have dependencies outside A (except to the shared part).

src\
   +-- shared 
   |     \ ...
   +-- comp-A
   |     \ ...
   +-- comp-B
   |     \ ...
   ...

Note that there is no naming collision (nor package or file name).

Several executables and dll are built from each component, + fews dll from the shared components (no executables)

With ObjectAda, the C/C++ modules are compiled (MsVC toolchain) using a dedicated Makefile, and corresponding object files are bundled into a static lib. The Ada sources are all managed using a single (ObjectAda) "library", which allows (during dev) to "cherry pick" an executables to be build with a minimal rebuild of dependencies (only the effectively changed dependant packages).

For Gnat, I've wrote several GPR files:

src
| +-- product.gpr : an aggregate project of each component (sub-aggregate projects)
|
+-- shared 
|     +-- shared.gpr     : an aggregate project of the library and the dlls
|     +-- lib_shared.gpr : a static library project of all Ada packages
|     +-- dll_1.gpr      : a dynamic (encapsulated) library extending the lib_shared.gpr
|     +-- dll_2.gpr      : ...
+-- comp-A
|     +-- comp-A.gpr     : an aggregate project of the library, executables and dlls
|     +-- lib_comp-A.gpr : a static library project of all Ada packages (executables excluded)
|     +-- exe_comp-A.gpr : a standard project (including the lib through "with" clause) with Main 
|     |                    and link instructions for every executables
|     +-- dll_A1.gpr     : a dynamic (encapsulated) library extending the lib_comp-A.gpr
|     +-- dll_A2.gpr     : ...
+-- comp-B
|     | (same as comp-A)
 ...

(I've kept the static lib of the C/C++ content up to now, but the goal is to also move this part to Gnat).

This structure works well to build the overall product (all executables and dll) - typically on CI, but is not ideal for the development phase (eg build a single executable, while other parts of the basecode is "in edition" - and cannot be compiled yet), because it move the dependencies from package level to library (component) level.

Do you see a better way to deal with the GPR, or should I switch to Makefile (Gnatmake / Gnatdll)?