Make transition_sa and transition_sg constructors constexpr - #714
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kris-jusiak merged 1 commit intoJul 12, 2026
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Every fully-formed transition variant's constructor is already constexpr, but the two anonymous-transition intermediates built from a target state -- transition_sa (state + action) and transition_sg (state + guard) -- were missed. Without constexpr on these, a transition table containing such a row can't be built in a constant expression, so an sm<> whose table contains one can't be constinit / statically initialized. Both constructors have empty bodies that forward to already-constexpr base constructors, so this is a one-word change per type with no behavioral or ABI impact -- constexpr on a constructor is purely permissive. Add a regression test (test/ft/constexpr.cpp) that statically initializes an sm<> whose table contains both an anonymous guarded transition (transition_sg) and an anonymous action transition (transition_sa); it fails to compile without the fix.
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Thanks @cierny |
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Every fully-formed
transition<…>constructor is alreadyconstexpr, but the two anonymous-transition intermediates are not:transition_saandtransition_sg.This meant a transition table containing such a row couldn't be built in a constant expression, blocking
constinit/ static initialization of ansm<>that uses one.Both just forward to already-
constexprbase constructors, so it's a one-word change per type with no behavioral or ABI impact. Includes a regression test intest/ft/constexpr.cppthat fails to compile without the fix.