[native] Remove std::format from the CoreCLR host

[simonrozsival]

Part of #12533 (the CoreCLR follow-up to #12139). Stacked on top of #12524.

Why

std::format is by far the biggest single contributor of libc++ symbols in the native host. Every translation unit that formats any value pulls in std::to_chars for float, double and long double, plus std::locale, std::numpunct and std::use_facet — about 15 symbols per object file, whether or not the code ever formats a floating point number.

What

Converts every std::format-based logging call site reachable from the CoreCLR lane to the printf-style log_debugf / log_infof / log_warnf / log_errorf functions that already exist in common/include/shared/log_functions.hh.

This is not just a mechanical swap — unlike the std::format macros, these are annotated with __attribute__((format(printf, ...))), so the compiler now type-checks every format specifier against its argument. -Wformat / -Werror=format-security are already enabled, and the build is clean.

Helpers::abort_application (CAT, std::format (…)) call sites move to the previously unused Helpers::abort_applicationf overload. That overload was only defined in the CoreCLR lane, so an identical definition is added to mono/shared/helpers.cc.

Several of the converted files live in common/ rather than clr/. Those are header-inlined into CoreCLR objects (dso-loader.hh, mainthread-dso-loader.hh, monodroid-dl.hh, …), so leaving them alone would have left the std::format payload in host.cc.o regardless. log_*f is defined in both the CoreCLR and MonoVM lanes, so converting them is safe for Mono too — verified by building it.

Bonus: fixes a latent NativeAOT logging bug

clr/host/bridge-processing.cc is compiled into both the CoreCLR and the NativeAOT hosts. NativeAOT's log_types.hh is a 5-line stub, so those calls fell through to the printf-style macros in java-interop-logger.h — which have no format(printf) attribute, so nothing warned. In NativeAOT builds they printed a literal {} instead of the value. Both sites are now correct in both lanes.

Results

Measured on the arm64 Release CoreCLR archive (libnet-android.release-static-release.a), counting undefined std::__ndk1::* / operator new / operator delete / __cxa_* symbols. Baseline is this PR's base, #12524:

	before	after
undefined libc++ refs	142	76 (−46%)
objects with the std::format fingerprint	4	0

Per-object, before → after:

object	before	after
host.cc.o	41	27
assembly-store.cc.o	35	20
typemap.cc.o	22	5
bridge-processing.cc.o	22	2

The std::format fingerprint (co-occurrence of to_chars<float/double/long double> with locale / numpunct / use_facet) is now absent from every object file in the archive.

Deleting the machinery

With the last call site gone, the std::format macros and templates in clr/include/shared/log_types.hh have no users left, so this PR deletes them too. That file is now identical to the existing NativeAOT stub. This generates no code change on its own — the templates were never instantiated, which is why the counts above already show the std::format fingerprint gone — but it means std::format can no longer be reintroduced into the CoreCLR host by accident.

The std::string_view overload of log_write goes with it. It was duplicated in the CoreCLR and MonoVM copies of log_types.hh and existed only so call sites passing a string literal wouldn't have to write .data (). It had four users, all in timing-internal.cc: three pass a literal and now bind to the plain const char* overload, and the fourth passes a view produced by FastTiming::dump () and now uses log_writef () with %.*s.

That last one also retires a fragile invariant. The overload called .data (), so it required a NUL-terminated string — but dump () builds its views from a buffer plus an explicit length. They are all NUL-terminated today and nothing enforced it. %.*s honours the length instead.

std::format is now completely absent from the clr/, common/ and nativeaot/ trees:

lane	std::format	#include <format>
clr/	0	0
common/ (shared)	0	0
nativeaot/	0	0
mono/	45	2

Verification

Built all three runtime lanes locally for arm64-v8a Release — CoreCLR, MonoVM and NativeAOT — with zero errors and zero new warnings. Building MonoVM caught a real link error (the missing abort_applicationf definition) that a CoreCLR-only build would have missed.

Not in this PR

• Converting the remaining mono/-only call sites, and deleting the std::format machinery from mono/shared/log_types.hh.
• Removing the remaining std::string / std::function / std::mutex usage from host.cc and assembly-store.cc (the 76 remaining refs).
• Dropping the CplusPlusArchive entries from NativeRuntimeComponents.cs — the last step, once the archives are genuinely unreferenced.

[Copilot]

Pull request overview

This PR continues the CoreCLR-host libc++ reduction work by removing std::format usage from CoreCLR-reachable native host code paths and switching logging/abort call sites to the existing printf-annotated log_*f / Helpers::abort_applicationf APIs. This reduces libc++ symbol pull-in while also making format/argument mismatches compiler-checked.

Changes:

• Replaced std::format-style logging with log_debugf / log_infof / log_warnf / log_errorf across CoreCLR host/runtime-base code and shared native headers.
• Added Helpers::abort_applicationf definition to the Mono shared lane and migrated CoreCLR abort call sites to the abort_applicationf overload.
• Adjusted a few debug-only type/name helpers and log strings to avoid std::string_view/std::format dependencies in CoreCLR code paths.

Show a summary per file

File	Description
src/native/mono/shared/helpers.cc	Adds Helpers::abort_applicationf implementation for the Mono lane.
src/native/common/include/runtime-base/timing-internal.hh	Switches warning logs to log_warnf (printf-style).
src/native/common/include/runtime-base/system-loadlibrary-wrapper.hh	Converts debug logs to log_debugf.
src/native/common/include/runtime-base/mainthread-dso-loader.hh	Removes <format> usage and converts logs/abort to printf-style formatting.
src/native/common/include/runtime-base/dso-loader.hh	Converts loader tracing/error logs to printf-style formatting.
src/native/clr/runtime-base/android-system.cc	Converts environment/system-property diagnostics to printf-style logs.
src/native/clr/pinvoke-override/precompiled.cc	Removes <format> usage and converts abort/log statements to abort_applicationf/log_debugf.
src/native/clr/include/runtime-base/monodroid-dl.hh	Converts DSO cache and symbol-lookup logs to printf-style formatting.
src/native/clr/include/runtime-base/android-system.hh	Converts debug log to log_debugf.
src/native/clr/include/host/typemap.hh	Replaces debug label std::string_view constants with const char* and updates debug signatures.
src/native/clr/include/host/pinvoke-override-impl.hh	Converts p/invoke override diagnostics to printf-style logging.
src/native/clr/host/typemap.cc	Converts typemap debug/release tracing to printf-style logging and updates helper signatures.
src/native/clr/host/host.cc	Converts CoreCLR host logging/abort paths to printf-style formatting and adds <cinttypes> usage.
src/native/clr/host/fastdev-assemblies.cc	Converts FastDev logs and aborts to printf-style formatting.
src/native/clr/host/bridge-processing.cc	Converts GC-related logs to log_*f formatting (including NativeAOT-shared TU).
src/native/clr/host/assembly-store.cc	Removes std::format usage (including hex formatting) and converts cache/store logging and aborts to printf-style formatting.

Review details

• Files reviewed: 16/16 changed files
• Comments generated: 2
• Review effort level: Lite