src/lisp/error.h

#pragma once

#include <stdbool.h>

// Error handling code

struct eloc
{
	int line;
	char *file;
};

enum error_code
{
	EOK = 0,
	/// Expected something but didn't get it. if this is in a
	/// safe_state we should probably just re-try.
	EEXPECTED,
	/// An invalid token was present in the input
	EINVALID,
	/// A structure was malformed
	EMALFORMED,
	/// The arguments provided were invalid
	EARGS,
	/// An external resource (say, a file) was not found
	ENOTFOUND,
	/// This is unimplemented
	EUNIMPL,
};

struct error
{
	enum error_code code;
	// Is any state safe? I.e. can we continue or must we panic?
	bool safe_state;
	struct eloc loc;
	char *message;
};

#define E_DEBUG(_e, _m) // edebug(_e, __FILE__, __LINE__, __func__, _m)
#define E_INIT()								\
	struct error __error = { 0 };
#define NEARVAL(val)							\
	__error.loc.line = cons_line(val),			\
		__error.loc.file = cons_file(val)
#define NEARIS(is) (is)->getpos((is), &__error.loc.line, &__error.loc.file)
#define _TRY(expr, m, c)								\
	{													\
		struct error __sub = (expr);					\
		if (__sub.code)									\
		{												\
			if (!__sub.loc.file || !__sub.loc.line)		\
				__sub.loc.file = __error.loc.file,		\
					__sub.loc.line = __error.loc.line;	\
			if (c)										\
				__sub.code = c;							\
			char *__m = m;								\
			if (__m)									\
				__sub.message = __m;					\
			E_DEBUG(__sub, #expr);						\
			return __sub;								\
		}												\
	}
#define TRY(expr) _TRY(expr, NULL, 0)
#define TRY_ELSE(expr, c, ...) _TRY(expr, ehsprintf(__VA_ARGS__), c)
#define OKAY() return __error
#define THROW(_c, ...)													\
	{																	\
		__error.code = (_c);											\
		__error.message = ehsprintf(__VA_ARGS__);						\
		E_DEBUG(__error, "throwing");									\
		return __error;													\
	}
#define THROWSAFE(_c)													\
	{																	\
		__error.code = (_c);											\
		__error.safe_state = true;										\
		E_DEBUG(__error, "safe");										\
		return __error;													\
	}

#define IS_OKAY(e) ((e).code == EOK)
#define OKAY_IF(val)													\
	{																	\
		struct error __sub_of = (val);									\
		if (IS_OKAY(__sub_of))											\
			OKAY();														\
		if (!__sub_of.safe_state)										\
			TRY(__sub_of);												\
	}

#define WARN_UNUSED __attribute__((warn_unused_result))

// error heap string print formatted
// returns a heap-allocated string.
char *ehsprintf(const char *msg, ...);

void ereport(struct error err);

void edebug(struct error err, char *file, int line, const char *func, const char *why);

#define UNUSED(val) (void)(val)