From 9382a3ad58536d84757fd15cf8105969fc4654ba Mon Sep 17 00:00:00 2001
From: Devin Hussey <husseydevin@gmail.com>
Date: Wed, 20 Mar 2019 15:03:27 -0400
Subject: [PATCH] C11 conformance: Add _Noreturn, stdnoreturn.h, and partial
 _Alignas support

_Noreturn, just like __attribute__((noreturn)), is ignored.
I also added stdnoreturn.h, in all its glorious uselessness.

_Alignas only works for integer expressions right now. In order
to comply, we need:
 - _Alignas(type) -> _Alignas(_Alignof(type)).
 - stdalign.h as soon as it is done.

Note: DR 444 is supported; it works on struct members.

Signed-off-by: Devin Hussey <husseydevin@gmail.com>
---
 include/stdnoreturn.h |  7 +++++++
 tccgen.c              | 38 +++++++++++++++++++++++++++++++++++++-
 tcctok.h              |  2 ++
 3 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 include/stdnoreturn.h

diff --git a/include/stdnoreturn.h b/include/stdnoreturn.h
new file mode 100644
index 00000000..4d580ea5
--- /dev/null
+++ b/include/stdnoreturn.h
@@ -0,0 +1,7 @@
+#ifndef _STDNORETURN_H
+#define _STDNORETURN_H
+
+/* ISOC11 noreturn */
+#define noreturn _Noreturn
+
+#endif /* _STDNORETURN_H */
diff --git a/tccgen.c b/tccgen.c
index 8c6bdfa0..c6edcc3f 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -4172,6 +4172,22 @@ static int parse_btype(CType *type, AttributeDef *ad)
         case TOK_INT:
             u = VT_INT;
             goto basic_type;
+        case TOK_ALIGNAS:
+            { int n;
+            next();
+            /* TODO: _Alignas(type) -> _Alignas(_Alignof(type)) */
+            if (tok == '(') {
+                next();
+                n = expr_const();
+                if (n <= 0 || (n & (n - 1)) != 0)
+                    tcc_error("alignment must be a positive power of two");
+                skip(')');
+            } else {
+                 expect("(");
+            }
+            ad->a.aligned = exact_log2p1(n);
+          }
+          continue;
         case TOK_LONG:
             if ((t & VT_BTYPE) == VT_DOUBLE) {
                 t = (t & ~(VT_BTYPE|VT_LONG)) | VT_LDOUBLE;
@@ -4281,7 +4297,11 @@ static int parse_btype(CType *type, AttributeDef *ad)
             t |= VT_INLINE;
             next();
             break;
-
+        case TOK_NORETURN3:
+            /* currently, no need to handle it because tcc does not
+               track unused objects */
+            next();
+            break;
             /* GNUC attribute */
         case TOK_ATTRIBUTE1:
         case TOK_ATTRIBUTE2:
@@ -4569,6 +4589,22 @@ static CType *type_decl(CType *type, AttributeDef *ad, int *v, int td)
         case TOK_RESTRICT2:
         case TOK_RESTRICT3:
             goto redo;
+        case TOK_ALIGNAS:
+            { int n;
+            next();
+            /* TODO: _Alignas(type) -> _Alignas(_Alignof(type)) */
+            if (tok == '(') {
+                next();
+                n = expr_const();
+                if (n <= 0 || (n & (n - 1)) != 0)
+                    tcc_error("alignment must be a positive power of two");
+                skip(')');
+            } else {
+                expect("(");
+            }
+            ad->a.aligned = exact_log2p1(n);
+          }
+          break;
 	/* XXX: clarify attribute handling */
 	case TOK_ATTRIBUTE1:
 	case TOK_ATTRIBUTE2:
diff --git a/tcctok.h b/tcctok.h
index 64c579c9..a3befd65 100644
--- a/tcctok.h
+++ b/tcctok.h
@@ -54,6 +54,7 @@
      DEF(TOK_ALIGNOF1, "__alignof")
      DEF(TOK_ALIGNOF2, "__alignof__")
      DEF(TOK_ALIGNOF3, "_Alignof")
+     DEF(TOK_ALIGNAS, "_Alignas")
      DEF(TOK_TYPEOF1, "typeof")
      DEF(TOK_TYPEOF2, "__typeof")
      DEF(TOK_TYPEOF3, "__typeof__")
@@ -138,6 +139,7 @@
      DEF(TOK_NODECORATE, "nodecorate")
      DEF(TOK_NORETURN1, "noreturn")
      DEF(TOK_NORETURN2, "__noreturn__")
+     DEF(TOK_NORETURN3, "_Noreturn")
      DEF(TOK_VISIBILITY1, "visibility")
      DEF(TOK_VISIBILITY2, "__visibility__")