Stability

Eskiu is stable since 0.12: code that compiles with 0.12.0 keeps compiling in every 0.12.x release. Before 1.0 a minor release (0.13, 0.14) can still change the language or the standard library, but every change that can break a program follows the rules below, so code moves forward with warnings instead of failing to compile.

Standard library names

• A public name (one without a leading _) is not renamed or removed in a patch release (0.12.0 to 0.12.1).
• A rename in a minor release keeps the old name for that release as a wrapper marked deprecated("use NEW"). Each use prints a warning that names the replacement; the next minor release removes it. -Wno-deprecated silences the warnings.
• The CHANGELOG lists every renamed or removed name with its replacement.
• Names that start with _ are internal. They can change in any release.

The language

• A change that makes a valid program invalid (a new error, a new keyword, a different meaning) lands in a minor release and is listed in the CHANGELOG under "Changed", with what to edit. When the old form can be detected, the release before warns about it first.
• New syntax uses contextual words where it can (deprecated is not a keyword), so existing names keep working.
• Patch releases only fix bugs. A fix can still reject a program the compiler accepted by mistake (for example code that miscompiled); the CHANGELOG says so.

deprecated

A function marked deprecated still works:

int Rect_area(const Rect* self) { return self.w * self.h; }
deprecated("use Rect_area") int rect_area(const Rect* r) { return Rect_area(r); }

A call to rect_area prints warning: 'rect_area' is deprecated: use Rect_area, at the call. Uses inside an imported module are not reported, so a library can keep a wrapper that calls another deprecated name without warning its users.

What is stable

The C ABI of extern functions, the object files and the command-line flags of eskiuc documented in eskiuc --help follow the same rules as the standard library.