Context and shared ptr improvements

[Reneg973]

Fixes # (issue)
non, just improvements

Changes

non-API changes in Context and nostd::shared_ptr

Please provide a brief description of the changes here.

• may reduce sizeof(nostd::shared_ptr) and therefore sizeof(Context), if sizeof(std::shared_ptr) == 16 instead of 32
• prevent dynamic allocation in case of short keys (SSO)
• may perform faster because of removed vtable functions

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[Reneg973]

missing header <string> for self sufficiency in context.h, will update it later

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.90%. Comparing base (70daba9) to head (923bc47).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
api/include/opentelemetry/nostd/shared_ptr.h	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3713      +/-   ##
==========================================
+ Coverage   89.90%   89.90%   +0.01%     
==========================================
  Files         225      225              
  Lines        7281     7095     -186     
==========================================
- Hits         6545     6378     -167     
+ Misses        736      717      -19     

Files with missing lines	Coverage Δ
api/include/opentelemetry/context/context.h	100.00% <100.00%> (ø)
api/include/opentelemetry/nostd/shared_ptr.h	96.83% <75.00%> (-3.17%)	⬇️

... and 46 files with indirect coverage changes

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[Copilot]

Pull Request Overview

This PR optimizes the Context and nostd::shared_ptr implementations by reducing memory overhead and eliminating dynamic memory allocations. The changes improve performance through more efficient memory management, removal of virtual function overhead, and enabling SSO (Small String Optimization) for context keys.

Key changes:

• Removes virtual functions from shared_ptr_wrapper to eliminate vtable overhead
• Uses std::string for context keys instead of raw char* to enable SSO and simplify memory management
• Dynamically sizes PlacementBuffer based on shared_ptr_wrapper size to potentially reduce sizeof(shared_ptr)

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
api/include/opentelemetry/nostd/shared_ptr.h	Removes virtual functions, dynamically sizes placement buffer, adds self-assignment checks, fixes unique_ptr conversion
api/include/opentelemetry/context/context.h	Replaces manual key memory management with std::string, simplifies key comparison, marks methods const-correct
.vscode/launch.json	Removes IDE-specific configuration file

[Copilot]

Using std::move() on a nostd::unique_ptr will not work correctly. The original code with other.release() was correct. nostd::unique_ptr may not have a move constructor that works with std::shared_ptr, but it does have a release() method that returns the raw pointer. This change will likely cause compilation errors or incorrect behavior.

Suggested change

	std::shared_ptr<T> ptr_(std::move(other));
	std::shared_ptr<T> ptr_(other.release());

[Reneg973]

I don't get this!
According to cppref(constructor 13) this constructor exists. Additionally nostd::unique_ptr implements move operations perfectly.
Also, if this would be true, then code like:

nostd::unique_ptr<T> Foo() { return new T; }
std::shared_ptr<T> ptr(Foo());

would not work.

PS: GPT-5 says everything is fine with this code

[owent]

As I understand it, std::shared_ptr should not recognize nostd::unique_ptr and cannot be constructed from its rvalue.

[Reneg973]

As I understand it, std::shared_ptr should not recognize nostd::unique_ptr and cannot be constructed from its rvalue.

Perfect, I was blind and naive. Thought I saw a test for it, but didn't. After writing one I directly had compiler error.

[Copilot]

Extra space before closing parenthesis in initializer list.

Suggested change

	, value_( value)
	, value_(value)