From 31f6b60f650a72d7727d386cef160f4baae70f38 Mon Sep 17 00:00:00 2001
From: lemon <lsof@mailbox.org>
Date: Thu, 11 Dec 2025 17:57:07 +0100
Subject: _Alignof and stuff

---
 c/c.c           | 29 ++++++++++++++++++-----------
 common.h        |  2 ++
 embedfilesdir.c |  9 +++++++++
 io.c            |  4 ++--
 test/13-c11.c   | 22 ++++++++++++++++++++++
 5 files changed, 53 insertions(+), 13 deletions(-)
 create mode 100644 test/13-c11.c

diff --git a/c/c.c b/c/c.c
index d5e4d9e..259058f 100644
--- a/c/c.c
+++ b/c/c.c
@@ -443,13 +443,17 @@ subscriptcheck(const struct expr *ex, const struct expr *rhs, const struct span
    return ty;
 }
 
-static void /* 6.5.3.4 The sizeof operator */
-sizeofcheck(const struct span *span, union type ty)
+static void /* 6.5.3.4 The sizeof and _Alignof operators */
+sizeofalignofcheck(const struct span *span, enum toktag tt, union type ty, const struct expr *ex)
 {
    if (isincomplete(ty))
-      error(span, "cannot apply sizeof to incomplete type '%ty'", ty);
+      error(span, "cannot apply %'tt to incomplete type '%ty'", tt);
    else if (ty.t == TYFUNC)
-      error(span, "cannot apply sizeof to function type '%ty'", ty);
+      error(span, "cannot apply %'tt to function type '%ty'", tt);
+   else if (tt == TKWsizeof && ex && ex->t == EGETF && ex->fld.bitsiz)
+      error(span, "cannot apply %'tt to bitfield", tt);
+   if (tt != TKWsizeof && ex && ccopt.pedant)
+      warn(span, "%'tt applied to an expression is a GNU extension", tt);
 }
 
 static bool /* 6.5.8 Relational operators */
@@ -998,25 +1002,28 @@ Unary:
          ex = mkexpr(ESYM, tk.span, decl->ty, .qual = decl->qual, .sym = decl);
       }
       break;
-   case TKWsizeof:
+   case TKWsizeof: case TKW_Alignof: case TKWalignof:
       span = tk.span;
-      if (!match(cm, NULL, '(')) /* sizeof expr */
+      if (!match(cm, NULL, '(')) /* sizeof/alignof expr */
          goto Unops;
-      else if (isdecltok(cm)) { /* sizeof (type) */
+      else if (isdecltok(cm)) { /* sizeof/alignof (type) */
+         enum toktag tt = tk.t;
          struct declstate st = { DCASTEXPR };
          ty = pdecl(&st, cm).ty;
          peek(cm, &tk);
          if (expect(cm, ')', NULL))
             joinspan(&span.ex, tk.span.ex);
-      } else { /* sizeof expr */
+         sizeofalignofcheck(&span, tt, ty, NULL);
+      } else { /* sizeof/alignof expr */
+         enum toktag tt = tk.t;
          tmp = commaexpr(cm);
          peek(cm, &tk);
          if (expect(cm, ')', NULL))
             joinspan(&span.ex, tk.span.ex);
          ppostfixopers(cm, &tmp);
          ty = tmp.ty;
+         sizeofalignofcheck(&span, tt, ty, &tmp);
       }
-      sizeofcheck(&span, ty);
       ex = mkexpr(ENUMLIT, span, mktype(targ_sizetype), .u = typesize(ty));
       break;
    case TKW__builtin_va_arg:
@@ -1081,8 +1088,8 @@ Unary:
                error(&span, "cannot take address of bitfield");
             ex = mkexpr(EADDROF, span, mkptrtype(ex.ty, ex.qual), .sub = exprdup(cm, &ex));
             break;
-         case TKWsizeof:
-            sizeofcheck(&span, ex.ty);
+         case TKWsizeof: case TKW_Alignof: case TKWalignof:
+            sizeofalignofcheck(&span, unops[nunop].tt, ex.ty, &ex);
             ex = mkexpr(ENUMLIT, span, mktype(targ_sizetype), .u = typesize(ex.ty));
             break;
          default: assert(0);
diff --git a/common.h b/common.h
index ce7d604..2b2bfd7 100644
--- a/common.h
+++ b/common.h
@@ -16,6 +16,7 @@ typedef unsigned short ushort;
 typedef unsigned long long uvlong;
 typedef   signed long long vlong;
 typedef unsigned uint;
+
 #if __STDC_VERSION__ >= 202311L
 #define NORETURN [[noreturn]]
 #elif __STDC_VERSION__ >= 201112L
@@ -29,6 +30,7 @@ typedef unsigned uint;
 #else
 #define HAS_BUILTIN(_) 0
 #endif
+
 #define static_assert(x) _Static_assert(x, #x)
 #define in_range(x, Lo, Hi) ((uint) (x) - (Lo) <= (Hi) - (Lo)) /* lo <= x <= hi; lo > 0, hi > 0 */
 #define alignup(x, A) (((x) + ((A) - 1)) & -(A))
diff --git a/embedfilesdir.c b/embedfilesdir.c
index 72a2ce1..7d97f98 100644
--- a/embedfilesdir.c
+++ b/embedfilesdir.c
@@ -85,6 +85,15 @@ typedef __builtin_va_list __gnuc_va_list;\n\
 
 {"stdnoreturn.h", S("\
 #define noreturn _Noreturn\n\
+")},
+
+{"stdalign.h", S("\
+#if __STDC_VERSION__ < 202311L\n\
+#define alignas _Alignas\n\
+#define alignof _Alignof\n\
+#define __alignas_is_defined 1\n\
+#define __alignof_is_defined 1\n\
+#endif\n\
 ")},
 
    {NULL}
diff --git a/io.c b/io.c
index b2d4364..dc4cd5d 100644
--- a/io.c
+++ b/io.c
@@ -595,8 +595,8 @@ vbfmt(struct wbuf *out, const char *fmt, va_list ap)
                   #include "c/keywords.def"
                   #undef _
                   };
-                  n += bfmt(buf, "%s", tab[tok->t - TKWBEGIN_]);
-                  break;
+                  tok->s = tab[tok->t - TKWBEGIN_];
+                  tok->len = strlen(tok->s);
                }
                goto Tok;
             }
diff --git a/test/13-c11.c b/test/13-c11.c
new file mode 100644
index 0000000..479c2d7
--- /dev/null
+++ b/test/13-c11.c
@@ -0,0 +1,22 @@
+/* CFLAGS: -std=c11 -Werror */
+/* EXPECT:
+*/
+
+#include <stdlib.h>
+#include <stdnoreturn.h>
+#include <stdalign.h>
+
+noreturn void quit(int x) {
+   exit(x);
+}
+
+int foo(int x) {
+   if (x < 0) quit(alignof(int *));
+   else return x;
+}
+
+struct x{int h:2;} X;
+int main(int argc, char **argv) {
+   return foo(0);
+}
+
-- 
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