[charlesnicholson]

build.bat under Visual Studio 2022 stops on error C2220 partway through the conformance suite. 32 lines in tests/conformance.c each raise C4127, "conditional expression is constant", and that build has carried /WX for a long time.

CI never saw it: the windows-latest runner is on Visual Studio 2026 (v18.9.1), whose front end no longer reports C4127 for these. So main is green on the runner and broken on a 2022 desktop.

The warnings

Two macros were the whole of it. Each wrapped its cases in a runtime if over a sizeof comparison the compiler folds away:

if (sizeof(type) <= sizeof(int)) { ... }                    /* NPF_TEST_WPROMO */
if (sizeof(int_least8_t) == sizeof(signed char)) { ... }    /* NPF_TEST_WSAME  */

C has no if constexpr to mark that as deliberate, so the guards move to the preprocessor, which answers the same questions from the type maxima <stdint.h> and <limits.h> already publish:

• a signed type is no wider than int exactly when its maximum fits in INT_MAX
• two integer types of one signedness hold the same values exactly when their maxima match — which is the property these cases actually rest on, more directly than sizeof equality does

Grouping cases under #if is what the rest of that section already does. Both macros lose a parameter and a nesting level as a result.

The policy

/WX is MSVC's -Werror, and three of the four compile-only targets — npf_static, use_npf_directly, wrap_npf — were building at the default warning level, so nothing they said could fail the build. They now carry the same /W4 /WX set as the unit and conformance builds, hoisted into one _CL_WARN_FLAGS so the policy lives in a single place.

All three were already clean at /W4. A survey run with /WX off across the whole matrix found C4127 to be the only warning the entire Windows build emits — 6208 of them, all from those 32 lines.

Verification

VS 2022 19.44.35228, full 2532-combo matrix, no shard:

config	before	after
Release / x64	error C2220, exit 1	clean, exit 0
Release / x86	—	clean, exit 0
Debug / x64	—	clean, exit 0

All three report PASSED: 3642306 assertions across 5064 objects — the same count the green VS 2026 CI run reports, so the #if guards select exactly what the runtime guards used to and no coverage was traded away. clang also compiles the file clean under the Makefile's -Wall -Wextra -Wundef -Werror in both C17 and C++20; -Wundef confirms every macro in the new #if lines is actually defined.

nanoprintf.h is untouched, so there is no code-size impact — cortex-m0/m4 -Os output is unchanged by construction.

🤖 Generated with Claude Code