This should never be used — especially not in production buildlogs — but it still exists.
The sane, correct ways of creating an error/warning all have annoying problems that this aims to solve:
#error/#pragma/_Pragmacan only be triggered or suppressed by preprocessor conditionals. This means that type-checking and other compile-time checks can't be performed._Static_assertprepends its own additional message about a failed static assertion which, while correct, obscures the source of fault for the developer. Sparkling errors are designed to look natural.
I initially planned on using this to generate better diagnostics for metaprogramming (see example.c) but this could (and definitely shouldn't!) be used to quote sections of the C standard or your own documents when printing an explicitly-checked-for error.
These headers rely on GCC not sanitizing comments when giving context for diagnostic messages, and not sanitizing the input string for gnu::error/gnu::warning attributes. Other attributes and printed sections are sanitized, so sadly this is the only way to do this. Read template.c for more details on usage.
This works on all recent versions of GCC, but not on Clang.