Make improvements

- Get threads working on NetBSD
- Get threads working on OpenBSD
- Fix Emacs config for Emacs v28
- Improve --strace logging of sigset_t
- Improve --strace logging of struct stat
- Improve memory safety of DescribeThing functions
- Refactor auto stack allocation into LIBC_RUNTIME
- Introduce shell.com example which works on Windows
- Refactor __strace_thing into DescribeThing functions
- Document the CHECK macros and improve them in NDEBUG mode
- Rewrite MAP_STACK so it uses FreeBSD behavior across platforms
- Deprecate and discourage the use of MAP_GROWSDOWN (it's weird)

libc/intrin/describeframe.c

@@ -0,0 +1,47 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/intrin/kprintf.h"
+#include "libc/macros.internal.h"
+#include "libc/runtime/memtrack.internal.h"
+#include "libc/runtime/runtime.h"
+
+#define ADDR(x)     ((int64_t)((uint64_t)(x) << 32) >> 16)
+#define UNSHADOW(x) ((int64_t)(MAX(0, (x)-0x7fff8000)) << 3)
+#define FRAME(x)    ((int)((x) >> 16))
+
+noasan const char *DescribeFrame(int x) {
+  /* asan runtime depends on this function */
+  char *p;
+  static char buf[32];
+  if (IsShadowFrame(x)) {
+    ksnprintf(buf, sizeof(buf), " /*shadow:%.12p*/", UNSHADOW(ADDR(x)));
+    return buf;
+    return " /*shadow*/ ";
+  } else if (IsAutoFrame(x)) {
+    return " /*automap*/";
+  } else if (IsFixedFrame(x)) {
+    return " /*fixed*/  ";
+  } else if (IsArenaFrame(x)) {
+    return " /*arena*/  ";
+  } else if (IsStaticStackFrame(x)) {
+    return " /*stack*/  ";
+  } else {
+    return "";
+  }
+}