0.11 - Configuring Your Compiler - Warning and Error Levels

During compilation, if you have done something that definitively violates the rules of the language, then your program is ill-formed.

In most cases, when the compiler encounters some kind of issue, it will emit diagnostic message (called diagnostic for short). The C++ standard does not define how diagnostics should be emitted, so the exact format and content of diagnostics will vary between different compilers. However, modern compilers have conventionally adopted the following:

• A diagnostic error (error for short) means the compiler has decided to halt compilation, because it either cannot proceed or deems the error serious enough to stop. When generated by the compiler, these are often called compilation errors, compiler errors, or compile errors.
• A diagnostic warning (warning for short) means the compiler has decided not to halt compilation.