Add WL_STR to define WL_String objects from string literals

wl.h

@@ -1,6 +1,8 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+#define WL_STR(X) ((WL_String) { (X), (int) sizeof(X)-1 })
+
 typedef struct WL_Runtime  WL_Runtime;
 typedef struct WL_Compiler WL_Compiler;
 
@@ -45,16 +47,85 @@ typedef struct {
     WL_String str;
 } WL_EvalResult;
 
+// Creates a compilation unit for a program
+// The provided arena (which can't be NULL) is
+// used for all memory allocations until a
+// program is produced or an error occurs.
+// If not enough memory is provided, NULL is
+// returned.
 WL_Compiler *wl_compiler_init(WL_Arena *arena);
+
+// Adds a file to the current compilation unit
+// and returns
+//
+//   WL_ADD_ERROR if an error occurred
+//
+//   WL_ADD_AGAIN if the file included a different
+//   file that also needs to be added to the unit,
+//   in which case the file name is in the "path"
+//   field of the return value.
+//
+//   WL_ADD_LINK all sources were processed and
+//   the unit is ready for linking
 WL_AddResult wl_compiler_add(WL_Compiler *compiler, WL_String path, WL_String content);
+
+// Links a compilation unit producing an executable.
+// The output program is just an array of bytes
+// allocated using the compiler's arena memory and
+// may be written to disk or any other external system
+// for caching.
+//
+// On error, -1 is returned and the error text can
+// be retrieved using wl_compiler_error. On success,
+// 0 is returned.
 int wl_compiler_link(WL_Compiler *compiler, WL_Program *program);
+
+// Returns the null-terminated error string for a
+// compilation unit that failed.
 WL_String wl_compiler_error(WL_Compiler *compiler);
+
+// Serializes the AST of the source parsed in this
+// compilation unit by writing the string to the
+// rovided buffer and returning the number of bytes
+// written to it.
+//
+// If the provided buffer is too small, the function
+// fills it up and returns the number of bytes that
+// would have been written if the buffer was large
+// enough. On error, -1 is returned.
 int wl_dump_ast(WL_Compiler *compiler, char *dst, int cap);
+
+// Writes the bytecode of a program to stdout as a
+// human-readable string.
 void wl_dump_program(WL_Program program);
 
+// Creates an evaluation context for a bytecode program
+// All memory used while running the program will be
+// allocated from the provided arena.
+//
+// If not enough memory was provided or the program is
+// invalid, NULL is returned.
 WL_Runtime *wl_runtime_init(WL_Arena *arena, WL_Program program);
+
+// Run the program associated to this runtime until an
+// event happens. The event may be one of:
+//
+//   WL_EVAL_DONE if execution is complete
+//
+//   WL_EVAL_ERROR if execution failed
+//
+//   WL_EVAL_OUTPUT if data is available for output,
+//   in which case the field "str" points to it
+//
+//   WL_EVAL_SYSVAR if the program requested the value
+//   of an external symbol.
+//
+//   WL_EVAL_SYSCALL
+//
 WL_EvalResult wl_runtime_eval(WL_Runtime *rt);
+
 WL_String     wl_runtime_error(WL_Runtime *rt);
+
 void          wl_runtime_dump(WL_Runtime *rt);
 
 bool wl_streq      (WL_String a, char *b, int blen);