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The API library is the base library for all *API libraries. It includes:

  • Info about the API library families
  • Execution Context Error Handling
  • Shared library API (for Stratify OS)


This is a simple static class to track the version and git hash of the library:

#include <api.hpp>
printf(  "Version:%s GitHash:%s\n",   api::ApiInfo::version(),   api::ApiInfo::git_hash())

Error Handling#

The *API family of libraries is designed to have at most one error per thread. There is one key axiom to follow to ensure proper error management:

Any method that can change the error context or relies on an error-free state must abort if the thread has an error.

The API library provides macros for error managing error handling. For system calls (that affect errno), use this sequence:

File& File::open(const char * path){    //abort if the context error is already set  API_RETURN_VALUE_IF_ERROR(-1) 
  //use this whenever errno could be affected  API_SYSTEM_CALL(path, open(path, O_RDWR))  return *this}
File& File::write(const void * buf, int nbyte){  API_RETURN_VALUE_IF_ERROR(-1)   API_SYSTEM_CALL("", write(fileno(), buf, nbyte))  return *this}
//This code allows the following sequence//if open fails, write will abortchar buffer[16]if( File().open("path").write(buffer, sizeof(buffer)).is_error() ){  //use api::ExecutionContext to look at the error  Printer() << api::ExecutionContext::error()}

When an error occurs, the api::ExecutionContext records the line number, a message, and a backtrace. You can use the error context to quickly find and fix errors.

Ignoring Errors#

Sometimes there is a need to ignore errors or to execute a system call even if the context has an error. The api::ErrorGuard class saves/restores the error context on construction/deconstruction.

File::~File(){  if( fileno() > 0 ){    //if the file is open, we want to close it even    //if the context has an error    api::ErrorGuard error_guard //save context and reset error    close()  } //~ErrorGuard() restores the error context (value of errno)}

Thread Safety#

errno is the mechanism for handling errors. errno is part of POSIX systems (Linux, Windows, Mac, and Stratify OS). On all supported systems, errno is thread-safe. &errno provides a unique signature for any method to resolve to the appropriate error context.

The API library automatically allocates an error context if an error context is requested in a new thread. Before the thread exits, it should call api::free_context(). If using the thread::Thread class for thread management, api::free_context() will be called automatically.