Add design spec for C++17 migration#96
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The project currently requires a binary/header-only install split due to C++14 lacking inline variables. This causes user-facing complexity with three extra CMake options and conditional compilation in bntables.h. Add a design document covering the migration plan from C++14 to C++17. This includes replacing constexpr/extern table patterns with inline constexpr, removing the OPENQMC_ENABLE_BINARY build machinery, updating documentation, and assessing NVCC compatibility risks. Assisted-by: Amp:claude-opus-4.6 Signed-off-by: Josh Bainbridge <josh.bainbridge@gmail.com>
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Apr 28, 2026
| C++17 introduces `inline` variable declarations. An `inline constexpr` | ||
| namespace-scope variable has external linkage and is guaranteed to have a | ||
| single definition across all translation units. This directly solves the | ||
| duplication problem with no build system workaround required. |
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Worth noting that OPENQMC_ENABLE_BINARY was solving two problems at once: C++14's internal-linkage duplication in the final binary, and having each TU parse ~393K lines of integer literals. C++17 inline constexpr fixes the duplication but reintroduces the per-TU parse cost. The spec should measure this on a representative consumer and accept the trade-off explicitly.
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This is great feedback. A really good point about the compiler time. I'll see if we can setup a test to verify the effect this change would have on this.
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The project currently requires a binary/header-only install split due to C++14 lacking inline variables. This causes user-facing complexity with three extra CMake options and conditional compilation in bntables.h. #86
Add a design document covering the migration plan from C++14 to C++17. This includes replacing constexpr/extern table patterns with inline constexpr, removing the OPENQMC_ENABLE_BINARY build machinery, and updating documentation.
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