e2 language testing space

Many languages attempt to be "memory safe" by processes such as reference counting, borrow checking, and mark-and-sweep garbage collection. These, for the most part, are guided towards preventing programmer error that causes use-after-frees, memory leaks, and similar conditions. We hereby refer to them as "conventional memory safety features".

However, in most cases, languages other than assembly (including these allegedly memory safe languages) do not handle stack overflows correctly; although dynamic allocation failures could be easily handled, correctly-written programs could crash when running out of stack space, with no method to detect this condition and fail gracefully.

Conventional memory safety features are not our priority, but we may choose to include them in the future, likely with reference counting while allowing weak pointers to be labelled.

General idea of how it should work

We haven't decided on general syntax yet. We generally prefer C-like syntax, although syntax inspired from other languages are occasionally used when appropriate; for example, multiple return values look rather awkward in the C syntax, so perhaps we could use Go syntax for that (func f(param1, param2) (return1, return2)), although we'd prefer naming parameters with type identifier rather than identifier type.

For stack safety: When defining a function, the programmer must specify what to do if the function could not be called (for example, if the stack is full). For example, malloc for allocating dynamic memory would be structured something like follows:

func malloc(size_t s) (void*) {
	/* What malloc is supposed to do */
	return ptr;
} onfail {
	return NULL;
}

If something causes malloc to be uncallable, e.g. if there is insufficient stack space to hold its local variables, it simply returns NULL as if it failed.

Other functions may have different methods of failure. Some might return an error, so it might be natural to set their error return value to something like ESTACK:

func f() (err) {
	return NIL;
} onfail {
	return ESTACK;
}

The above lets us define how functions should fail due to insufficient stack. This pattern is also useful outside of functions as a unit, therefore we introduce the following syntax for generic stack failure handling:

try {
	/* Do something */
} onfail {
	/* Do something else, perhaps returning errors */
}

Note that the onfail block must not fail; therefore, the compiler must begin to fail functions, whenever subroutines that those functions call have onfail blocks that would be impossible to fulfill due to stack size constraints.

Functions can be marked as nofail, in either the function definition or when calling it. A nofail specification when calling it overrides the function definition.

nofail func free() () {
	/* What free is supposed to do */
}

This will ensure that calling free can never fail due to lack of stack space. If such a case were to present itself, the compiler must make the caller fail instead. This is recursive, and thus you cannot create a loop of nofail functions. You may use canfail to be explicit about the reverse in function definitions, or to override a function when calling it. In the latter case, if the function does not define an onfail section, you must wrap it in a try {...} onfail {...} block.

Other non-trivial differences from C

1. Instead of errno, we use multiple return values to indicate errors where appropriate.
2. Minimize undefined behavior, and set stricter rules for implementation-defined behavior.
3. Support compile-time code execution.
4. More powerful preprocessor?