[SDK] Handle instrumentation object construction failures safely

[22elix3r]

Fixes #4361

Changes

Provider construction happens during SDK initialization. Runtime GetTracer / GetLogger / GetMeter calls must not throw. This change follows the post-SIG direction from @dbarker:

• Remove noexcept from the SDK constructors for TracerProvider, LoggerProvider, MeterProvider, Tracer, Logger, and Meter. Allocation or initialization failures during provider construction can now propagate so the caller (often the configuration library) can handle them.
• Keep GetTracer, GetLogger, and GetMeter noexcept. If constructing a previously unseen tracer/logger/meter fails, the provider catches the exception (when exceptions are enabled), logs via OTEL_INTERNAL_LOG_ERROR without letting logging escape, and returns a valid noop API object.
• The noop fallback is allocated during provider construction (new NoopTracer / NoopLogger / NoopMeter stored as a nostd::shared_ptr). Runtime failure handling does not allocate a fresh noop object.
• Failed construction is not inserted into the provider cache. A later Get* call can retry and return a normal SDK object once the failure is gone. Existing cached objects continue to be returned unchanged.
• The complete fallible path is protected: instrumentation-scope construction, configurator evaluation, object allocation, shared_ptr control-block allocation, cache insertion, and metrics AddMeter.
• Public API virtual method exception contracts are unchanged. ABI v1 and ABI v2 Get* signatures are unchanged. Try/catch is compiled only when OPENTELEMETRY_HAVE_EXCEPTIONS is set.

Tests added

• Constructor noexcept static_asserts for each signal.
• Deterministic fault injection through a ScopeConfigurator matcher that throws for a named scope.
• After failure, Get* returns a valid noop-compatible object, using it produces no telemetry, the cache is not poisoned, cached objects are unchanged, and a later call recovers when the injected failure is removed.
• Those tests are skipped when exceptions are disabled.

Validation

cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug \
  -DOTELCPP_WITH_EXAMPLES=OFF -DOTELCPP_BUILD_TESTING=ON \
  -DOTELCPP_WITH_OTLP_GRPC=OFF -DOTELCPP_WITH_OTLP_HTTP=OFF \
  -DOTELCPP_WITH_OTLP_FILE=OFF -DCMAKE_CXX_STANDARD=17

cmake --build build --target tracer_provider_test logger_provider_sdk_test meter_provider_sdk_test
ctest --test-dir build --output-on-failure \
  -R 'trace.(TracerProvider|TracerConfig)|logs.(LoggerProviderSDK|LoggerConfig)|metrics.(MeterProvider|MeterConfig)'
# 63/63 passed, including Get*ReturnsNoopOnConstructionFailure

ctest --test-dir build --output-on-failure -R 'logs.LoggerSDK'
# 12/12 passed

./build/sdk/test/metrics/meter_test
# 20/20 passed

# Exception-disabled compile of changed SDK sources:
g++ -std=c++17 -fno-exceptions -c -DOPENTELEMETRY_HAVE_EXCEPTIONS=0 ...
# tracer_provider.cc, tracer.cc, logger_provider.cc, logger.cc,
# meter_provider.cc, meter.cc: success

# ABI v2 compile of the three provider .cc files:
g++ -std=c++17 -c -DOPENTELEMETRY_ABI_VERSION_NO=2 ...
# tracer_provider.cc, logger_provider.cc, meter_provider.cc: success

git diff --check
# clean

tools/format.sh was not run: clang-format is not installed in this environment.

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed (SDK constructor exception specs only; API Get* contracts unchanged)

[codecov]

Codecov Report

❌ Patch coverage is 77.65957% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.08%. Comparing base (6af677c) to head (274e114).

Files with missing lines	Patch %	Lines
sdk/src/logs/logger_provider.cc	70.00%	9 Missing ⚠️
sdk/src/metrics/meter_provider.cc	80.00%	6 Missing ⚠️
sdk/src/trace/tracer_provider.cc	79.32%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4469      +/-   ##
==========================================
- Coverage   83.12%   83.08%   -0.03%     
==========================================
  Files         519      519              
  Lines       20256    20312      +56     
==========================================
+ Hits        16835    16875      +40     
- Misses       3421     3437      +16     

Files with missing lines	Coverage Δ
sdk/include/opentelemetry/sdk/metrics/meter.h	57.15% <ø> (ø)
sdk/include/opentelemetry/sdk/trace/tracer.h	100.00% <ø> (ø)
sdk/src/logs/logger.cc	94.12% <100.00%> (ø)
sdk/src/metrics/meter.cc	81.36% <100.00%> (ø)
sdk/src/trace/tracer.cc	80.22% <100.00%> (ø)
sdk/src/metrics/meter_provider.cc	87.18% <80.00%> (-6.15%)	⬇️
sdk/src/trace/tracer_provider.cc	83.96% <79.32%> (-4.75%)	⬇️
sdk/src/logs/logger_provider.cc	84.00% <70.00%> (-7.07%)	⬇️

... and 2 files with indirect coverage changes

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[22elix3r]

@dbarker Latest commits are up (format/IWYU follow-up + merge from main). CI is waiting on workflow approval again.

[Copilot]

Pull request overview

This PR updates the OpenTelemetry C++ SDK to safely handle failures during instrumentation object construction while preserving noexcept guarantees for runtime GetTracer/GetLogger/GetMeter calls by returning a pre-allocated noop fallback when construction fails (with exception handling compiled in only when exceptions are enabled).

Changes:

• Remove noexcept from SDK provider and instrumentation constructors so initialization failures can propagate to the caller.
• Keep provider Get* methods noexcept, adding guarded try/catch to log construction failures and return a pre-allocated noop object without poisoning caches.
• Add unit tests for constructor exception specs and deterministic fault injection/recovery behavior (skipped when exceptions are disabled).

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
sdk/test/trace/tracer_provider_test.cc	Adds static_asserts for constructor exception specs and tests noop fallback + recovery for GetTracer.
sdk/test/metrics/meter_provider_sdk_test.cc	Adds static_asserts and tests noop fallback + recovery for GetMeter.
sdk/test/logs/logger_provider_sdk_test.cc	Adds static_asserts and tests noop fallback + recovery for GetLogger; introduces a new test processor.
sdk/src/trace/tracer.cc	Removes noexcept from Tracer constructor implementation.
sdk/src/trace/tracer_provider.cc	Adds pre-allocated noop tracer fallback and exception-guarded construction in GetTracer.
sdk/src/metrics/meter.cc	Removes noexcept from Meter constructor implementation.
sdk/src/metrics/meter_provider.cc	Adds pre-allocated noop meter fallback and exception-guarded construction in GetMeter.
sdk/src/logs/logger.cc	Removes noexcept from Logger constructor implementation.
sdk/src/logs/logger_provider.cc	Adds pre-allocated noop logger fallback and exception-guarded construction in GetLogger.
sdk/include/opentelemetry/sdk/trace/tracer.h	Removes noexcept from Tracer constructor declaration.
sdk/include/opentelemetry/sdk/trace/tracer_provider.h	Removes noexcept from TracerProvider constructors; adds stored noop tracer member.
sdk/include/opentelemetry/sdk/metrics/meter.h	Removes noexcept from Meter constructor declaration.
sdk/include/opentelemetry/sdk/metrics/meter_provider.h	Removes noexcept from MeterProvider constructors; adds stored noop meter member.
sdk/include/opentelemetry/sdk/logs/logger.h	Removes noexcept from Logger constructor declaration.
sdk/include/opentelemetry/sdk/logs/logger_provider.h	Removes noexcept from LoggerProvider constructors; adds stored noop logger member.
CHANGELOG.md	Documents the SDK behavior change for constructor exception specs and noop fallback behavior.

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[22elix3r]

@dbarker IWYU and clang-tidy should be clean now. CountingProcessor uses std::move again, and the branch is merged onto latest main. Ready for another look when you have a minute.