new-module.md

Adding a New Module Library

Each ATTPCROOT module is a separate CMake shared library with an associated ROOT dictionary.

CMakeLists.txt Pattern

set(LIBRARY_NAME MyModule)
set(SRCS
   MyClass.cxx
   AnotherClass.cxx
)
set(DEPENDENCIES
   ATTPCROOT::AtData
   ROOT::Core
   FairRoot::Base
)

# Optional: unit tests
set(TEST_SRCS MyClassTest.cxx)
attpcroot_generate_tests(${LIBRARY_NAME}Tests SRCS ${TEST_SRCS} DEPS ${LIBRARY_NAME})

generate_target_and_root_library(
   ${LIBRARY_NAME}
   LINKDEF ${LIBRARY_NAME}LinkDef.h
   SRCS    ${SRCS}
   DEPS_PUBLIC ${DEPENDENCIES}
)

LinkDef File

Every class with a ClassDef macro in its header must appear in MyModuleLinkDef.h. ROOT uses this file to generate the dictionary.

#ifdef __CINT__
#pragma link off all globals;
#pragma link off all classes;
#pragma link off all functions;

#pragma link C++ class MyDataClass+;     // preferred for persisted classes
#pragma link C++ class MyTask-!;         // preferred for reflection-only code
#pragma link C++ class MyAlgorithm-!;

#endif

For the preferred streamer suffix rules, persisted-vs-non-persisted type rules, and notes on legacy LinkDef entries already in the tree, use guide.md.

Common FairTask Pattern

Most framework tasks follow:

• Init() load/register branches and initialize owned algorithms
• SetParContainers() load runtime-db containers when needed
• Exec() clear outputs, read the input TClonesArray and current event object, and write the next branch container

If a task reads or writes documented branches, update branch-io-contracts.md.

Registering with the Build

Add the new subdirectory to the top-level CMakeLists.txt:

add_subdirectory(MyModule)

And add ATTPCROOT::MyModule to the DEPENDENCIES of any module that needs it.