[CoreCLR/NativeAOT] Migrate JNI reference logging to printf

[simonrozsival]

Summary

Continue the printf-style logging migration introduced by #12140 by converting shared CoreCLR/NativeAOT JNI reference logging in OSBridge.

The src/native/clr/ location is shared infrastructure: the NativeAOT host explicitly compiles clr/host/os-bridge.cc, while MonoVM uses its separate mono/monodroid/osbridge.cc implementation. This PR therefore affects CoreCLR and NativeAOT, but not MonoVM.

Base/dependency: #12140 must merge first. This PR targets dev/simonrozsival/nativeaot-printf-logging so its diff contains only this migration.

Part of #12139.

Scope

Only two files change:

• src/native/clr/host/os-bridge.cc
• src/native/clr/include/host/os-bridge.hh

This does not overlap the open sibling work:

• [NativeAOT] Use POSIX primitives for GC bridge processing #12141 changes gc-bridge.cc/.hh — worker-thread and semaphore handoff;
• [NativeAOT] Reduce owning C++ standard library state #12142 changes logging/path ownership and source-location parsing elsewhere;
• [NativeAOT] Use indexed temporary peers in GC bridge #12145 changes bridge-processing.cc/.hh — temporary-peer graph storage;
• [NativeAOT] Migrate runtime utility logging to printf #12148 changes shared host/runtime utility logging.

Changes

Format reference records once

• add a private printf-checked OSBridge::log_itf() helper;
• use vasprintf() to produce one NUL-terminated reference-log line;
• pass the same formatted line to the existing logcat and file-writing path;
• release the C allocation after both destinations have consumed it;
• on allocation failure, fall back to the static format string rather than throwing from a noexcept std::format path.

Migrate JNI reference events

Replace six owning std::format constructions:

• new global reference;
• deleted global reference;
• new weak global reference;
• deleted weak global reference;
• new local reference;
• deleted local reference.

The replacements use %d, %p, %c, and %s with compiler format checking from the private helper declaration.

Remove ranges-heavy stack-trace splitting

• replace std::views::split with an in-place std::string_view newline scan;
• preserve empty, consecutive, and trailing lines;
• preserve logcat-only, file-only, and combined output behavior;
• write non-NUL-terminated line views with explicit lengths;
• convert stack-trace and raw gref logcat forwarding to %.*s / %s.

Responsibility boundary with #12141

• GCBridge ([NativeAOT] Use POSIX primitives for GC bridge processing #12141) controls when and where a bridge round runs: callback handoff, worker thread, semaphore synchronization, and Java GC triggering.
• OSBridge (this PR) tracks and logs JNI reference events: gref/weak-gref counters, reference creation/deletion lines, and optional stack traces.

The classes call each other through existing stable helpers, but this PR changes no GC scheduling, graph processing, callback lifecycle, or synchronization state.

Behavior preserved

• reference counters are incremented/decremented at the same points;
• logging remains gated by LOG_GREF / LOG_LREF before formatting;
• each reference line is still emitted to logcat and, when configured, the corresponding file;
• stack traces retain one output line per newline-delimited segment, including empty segments;
• logcat/file flushing behavior is unchanged;
• pointer, reference-type, thread-name, thread-id, and counter fields retain the same ordering and textual structure.

Measured impact

Android arm64 Release NativeAOT os-bridge.cc object, compiled with the repository-generated production NDK command:

Artifact	Before	After	Difference
os-bridge.cc.o	168,784 B	31,288 B	-137,496 B (-81.46%)
format/basic-string symbols	21	6	-15

The remaining C++ string symbols come from other shared header functionality; the six std::format reference-log instantiations are removed.

Non-goals

• no new logging test framework is introduced;
• no GC bridge synchronization or graph-processing code changes;
• no MonoVM osbridge.cc changes;
• no changes to the public logging helpers introduced by [Native] Add printf-style native logging #12140.

Validation

• git diff --check;
• no file overlap with [NativeAOT] Use POSIX primitives for GC bridge processing #12141, [NativeAOT] Reduce owning C++ standard library state #12142, [NativeAOT] Use indexed temporary peers in GC bridge #12145, or [NativeAOT] Migrate runtime utility logging to printf #12148;
• NDK Clang C++23 syntax compilation of all 36 Android arm64 Release NativeAOT source variants;
• NDK Clang C++23 syntax compilation of all 38 Android arm64 Release CoreCLR source variants;
• before/after NativeAOT object compilation and symbol inspection;
• focused read-only review of newline handling, allocation cleanup, OOM fallback, format types, category gating, and dual-destination output.

[Copilot]

Pull request overview

This PR continues the NativeAOT/CoreCLR printf-style logging migration by updating OSBridge’s JNI reference logging to avoid std::format (and std::views::split) while preserving the existing dual-destination behavior (logcat + optional files).

Changes:

• Introduces a private OSBridge::log_itf() helper that formats a single reference-log record via vasprintf() and forwards the same formatted line to logcat/file paths.
• Migrates gref/weak-gref/lref create/delete reference event logging to printf formatting (%d, %p, %c, %s) with compile-time format checking.
• Replaces ranges-based stack-trace splitting with an in-place std::string_view newline scan that preserves empty/trailing segments and writes non-NUL-terminated segments safely using explicit lengths.

Show a summary per file

File	Description
src/native/clr/include/host/os-bridge.hh	Updates the private logging helper signatures to use std::string_view and adds a printf-checked log_itf() declaration.
src/native/clr/host/os-bridge.cc	Implements log_itf() using vasprintf(), migrates reference event logging away from std::format, and replaces ranges-based stack-trace splitting with a manual string_view scan.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 0