int main(int argc, char **argv) {
// Debug flags
debug_gc = getEnvFlag("MINILISP_DEBUG_GC");
always_gc = getEnvFlag("MINILISP_ALWAYS_GC");
// Memory allocation
memory = alloc_semispace();
// Constants and primitives
Symbols = Nil;
void *root = NULL;
DEFINE2(env, expr);
*env = make_env(root, &Nil, &Nil);
define_constants(root, env);
define_primitives(root, env);
// The main loop
printf("%s", ">");
for (;;) {
*expr = read_expr(root);
if (!*expr)
return 0;
if (*expr == Cparen)
error("Stray close parenthesis");
if (*expr == Dot)
error("Stray dot");
print(eval(root, env, expr));
printf("\n%s", ">");
}
}
// Implements Cheney's copying garbage collection algorithm.
// http://en.wikipedia.org/wiki/Cheney%27s_algorithm
static void gc(void *root) {
assert(!gc_running);
gc_running = true;
// Allocate a new semi-space.
from_space = memory;
memory = alloc_semispace();
// Initialize the two pointers for GC. Initially they point to the beginning of the to-space.
scan1 = scan2 = memory;
// Copy the GC root objects first. This moves the pointer scan2.
forward_root_objects(root);
// Copy the objects referenced by the GC root objects located between scan1 and scan2. Once it's
// finished, all live objects (i.e. objects reachable from the root) will have been copied to
// the to-space.
while (scan1 < scan2) {
switch (scan1->type) {
case TINT:
case TSYMBOL:
case TPRIMITIVE:
// Any of the above types does not contain a pointer to a GC-managed object.
break;
case TCELL:
scan1->car = forward(scan1->car);
scan1->cdr = forward(scan1->cdr);
break;
case TFUNCTION:
case TMACRO:
scan1->params = forward(scan1->params);
scan1->body = forward(scan1->body);
scan1->env = forward(scan1->env);
break;
case TENV:
scan1->vars = forward(scan1->vars);
scan1->up = forward(scan1->up);
break;
default:
error("Bug: copy: unknown type %d", scan1->type);
}
scan1 = (Obj *)((uint8_t *)scan1 + scan1->size);
}
// Finish up GC.
#ifdef _WIN32
free(from_space);
#else
munmap(from_space, MEMORY_SIZE);
#endif
size_t old_nused = mem_nused;
mem_nused = (size_t)((uint8_t *)scan1 - (uint8_t *)memory);
if (debug_gc)
fprintf(stderr, "GC: %zu bytes out of %zu bytes copied.\n", mem_nused, old_nused);
gc_running = false;
}
