From a287fe5aeb6b681ab405c0297841dce64ab4b946 Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Fri, 14 Nov 2025 18:49:04 +0100
Subject: preeliminary va_list support

---
 c/builtin.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 c/builtin.c

(limited to 'c/builtin.c')

diff --git a/c/builtin.c b/c/builtin.c
new file mode 100644
index 0000000..d386480
--- /dev/null
+++ b/c/builtin.c
@@ -0,0 +1,101 @@
+#include "c.h"
+#include "../ir/ir.h"
+
+static bool
+callcheck(const struct span *span, int nparam, const union type *param, int narg, struct expr *args)
+{
+   bool ok = 1;
+   for (int i = 0, n = narg < nparam ? narg : nparam; i < n; ++i) {
+      if (!assigncheck(typedecay(param[i]), &args[i])) {
+         ok = 0;
+         error(&args[i].span, "arg #%d of type '%ty' is incompatible with '%ty'",
+               i, args[i].ty, param[i]);
+      }
+   }
+
+   if (narg > nparam) {
+      error(&args[nparam].span, "too many args to builtin function taking %d params", nparam);
+      ok = 0;
+   } else if (narg < nparam) {
+      error(span, "not enough args to builtin function taking %d param%s", nparam,
+            nparam != 1 ? "s" : "");
+      ok = 0;
+   }
+   return ok;
+}
+
+#define DEF_FNLIKE_SEMA(name, retty, ...)                                        \
+   static bool                                                                   \
+   name##_sema(struct comp *cm, struct expr *ex) {                               \
+      static union type par[] = { __VA_ARGS__, {0} };                            \
+      ex->ty = retty;                                                            \
+      return callcheck(&ex->span, arraylength(par)-1, par, ex->narg, ex->sub+1); \
+   }
+
+static bool
+va_start_sema(struct comp *cm, struct expr *ex)
+{
+   ex->ty = mktype(TYVOID);
+   return callcheck(&ex->span, 1, &cvalistty, ex->narg, ex->sub+1);
+}
+
+static union ref
+va_start_comp(struct function *fn, struct expr *ex, bool discard)
+{
+   assert(ex->t == ECALL && ex->narg == 1);
+   assert(ex->sub[1].ty.bits == cvalistty.bits);
+   if (!typedata[fn->fnty.dat].variadic)
+      error(&ex->span, "va_start used in non-variadic function");
+   addinstr(fn, mkinstr(Ovastart, 0, compileexpr(fn, &ex->sub[1], 0)));
+   return NOREF;
+}
+
+static bool
+va_end_sema(struct comp *cm, struct expr *ex)
+{
+   ex->ty = mktype(TYVOID);
+   return callcheck(&ex->span, 1, &cvalistty, ex->narg, ex->sub+1);
+}
+
+static union ref
+va_end_comp(struct function *fn, struct expr *ex, bool discard)
+{
+   return NOREF;
+}
+
+union ref
+builtin_va_arg_comp(struct function *fn, const struct expr *ex, bool discard)
+{
+   assert(ex->t == EVAARG && ex->ty.t);
+   enum irclass k = isagg(ex->ty) ? KPTR : type2cls[scalartypet(ex->ty)];
+   return addinstr(fn, mkinstr(Ovaarg, k, compileexpr(fn, ex->sub, 0), mktyperef(mkirtype(ex->ty))));
+}
+
+#define LIST_BUILTINS(_) \
+   _(va_start) \
+   _(va_end) \
+
+static const struct {
+   const char *name;
+   struct builtin b;
+} tab[] = {
+#define FNS(x) { "__builtin_" #x, { x##_sema, x##_comp } },
+   LIST_BUILTINS(FNS)
+#undef FNS
+};
+
+const char *intern(const char *);
+void
+putbuiltins(struct env *env)
+{
+   for (int i = 0; i < arraylength(tab); ++i) {
+      envadddecl(env, &(struct decl) {
+         .name = intern(tab[i].name),
+         .isbuiltin = 1,
+         .builtin = &tab[i].b,
+      });
+   }
+}
+
+
+/* vim:set ts=3 sw=3 expandtab: */
-- 
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