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C does not provide direct support to exception handling: it is the programmer's responsibility to prevent errors in the first place and test return values from the functions.
The implementation of exception handling in programming languages typically involves a fair amount of support from both a code generator and the runtime system accompanying a compiler. (It was the addition of exception handling to C++ that ended the useful lifetime of the original C++ compiler, Cfront. [18]) Two schemes are most common.
An exception handling mechanism allows the procedure to raise an exception [2] if this precondition is violated, [1] for example if the procedure has been called on an abnormal set of arguments. The exception handling mechanism then handles the exception. [3] The precondition, and the definition of exception, is subjective.
Microsoft Structured Exception Handling is the native exception handling mechanism for Windows and a forerunner technology to Vectored Exception Handling (VEH). [1] It features the finally mechanism not present in standard C++ exceptions (but present in most imperative languages introduced later).
The C++ standard library provides several levels of exception safety (in decreasing order of safety): [8] No-throw guarantee, also known as failure transparency: Operations are guaranteed to succeed and satisfy all requirements even in exceptional situations. If an exception occurs, it will be handled internally and not observed by clients.
If the expression within it is false, the macro will print a message to stderr and call abort(), defined in stdlib.h. The message includes the source filename and the source line number from the macros __FILE__ and __LINE__, respectively. [2] Since C99, the name of the function the assert statement is included as (__FUNC__) and the expression ...
The get_next_message() routine is typically provided by the operating system, and blocks until a message is available. Thus, the loop is only entered when there is something to process. function main initialize() while message != quit message := get_next_message() process_message(message) end while end function
As an example, in the Microsoft Visual C++ compiler, it causes omission of certain optimizations such as instruction reordering around calls to library functions, since such calls may cause input/output actions or accesses to memory locations marked volatile, and changes in the order of those change observable behavior.