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build_info.hpp

build_info — the git build hash plumbing for the §18.5 session header.

This header declares 1 free function.

Extracted from include/shulib/diag/build_info.hpp — this page is that header's documentation, reformatted, so it cannot disagree with the code. Prose about how to think about the API lives in the user guide; worked recipes live in the cookbook; this page is the complete, mechanical list of what exists.

Contents

compiledBuildHash

[[nodiscard]] constexpr std::string_view compiledBuildHash() noexcept

The build hash the build system injected, or EMPTY if it injected none. Empty means MISSING and must be rendered loudly (header note).

free function, declared at include/shulib/diag/build_info.hpp:36.

Design commentary, from the header

The header opens with the reasoning behind these shapes. It is reproduced here in full because a reference that only lists signatures teaches nobody why.

The header’s own reasoning — 27 lines 
 build_info — the git build hash plumbing for the §18.5 session header (WS13, C5).

 THE POINT: six months after a run, the log must say WHICH BINARY produced it.
 The hash therefore comes from the BUILD SYSTEM, never from code — code cannot
 know its own commit. The consuming build defines

     -DSHULIB_BUILD_HASH="\"<git describe --always --dirty>\""

 (test/CMakeLists.txt does exactly this for the host suite; the PROS Makefile
 gains the same line at R1). The --dirty suffix is NOT optional politeness: a
 clean-looking hash from a modified tree IS a wrong hash, and a wrong hash is
 worse than an absent one — it sends the 2am investigation to the wrong commit
 with full confidence.

 THE LOUDNESS CONTRACT (§18.5, the brief's landmine): when the macro is absent,
 compiledBuildHash() returns EMPTY, and every renderer treats empty as MISSING —
 an [ERROR] line in the session header, the literal token "MISSING" in the run
 summary. Nothing anywhere invents a plausible-looking placeholder. There is no
 "unknown"/"0000000" fallback BY DESIGN; grep for one before adding it, then
 don't.

 Header-only nuance, stated honestly: the macro is evaluated PER TRANSLATION
 UNIT. The value that reaches a log is the one seen by the TU that populated the
 SessionInfo (in practice: the one place a program builds its session header).
 A program that never defines the macro gets the loud MISSING path — which is
 correct, not a bug.

Last updated 2026-08-15 — published from the main release branch, commit fa545ff. This site tracks releases, so between them it can lag the repository — that lag is deliberate, and it is what keeps the development log off the public site. For the current state of the code, see the repository.