Make fixes and improvements

- Document more compiler flags
- Expose new __print_maps() api
- Better overflow checking in mmap()
- Improve the shell example somewhat
- Fix minor runtime bugs regarding stacks
- Make kill() on fork()+execve()'d children work
- Support CLONE_CHILD_CLEARTID for proper joining
- Fix recent possible deadlock regression with --ftrace

libc/intrin/strerror_wr.greg.c

@@ -0,0 +1,61 @@
+/*-*- 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 2022 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/bits/safemacros.internal.h"
+#include "libc/dce.h"
+#include "libc/fmt/fmt.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/macros.internal.h"
+#include "libc/nt/enum/formatmessageflags.h"
+#include "libc/nt/enum/lang.h"
+#include "libc/nt/process.h"
+
+/**
+ * Converts errno value to string with explicit windows errno too.
+ *
+ * @param err is error number or zero if unknown
+ * @return 0 on success, or error code
+ */
+privileged int strerror_wr(int err, uint32_t winerr, char *buf, size_t size) {
+  /* kprintf() weakly depends on this function */
+  int c, n;
+  char16_t winmsg[256];
+  const char *sym, *msg;
+  sym = firstnonnull(strerrno(err), "EUNKNOWN");
+  msg = firstnonnull(strerdoc(err), "No error information");
+  if (IsTiny()) {
+    if (!sym) sym = "EUNKNOWN";
+    for (; (c = *sym++); --size)
+      if (size > 1) *buf++ = c;
+    if (size) *buf = 0;
+  } else if (!IsWindows() || err == winerr || !winerr) {
+    ksnprintf(buf, size, "%s/%d/%s", sym, err, msg);
+  } else {
+    if ((n = FormatMessage(
+             kNtFormatMessageFromSystem | kNtFormatMessageIgnoreInserts, 0,
+             winerr, MAKELANGID(kNtLangNeutral, kNtSublangDefault), winmsg,
+             ARRAYLEN(winmsg), 0))) {
+      while ((n && winmsg[n - 1] <= ' ') || winmsg[n - 1] == '.') --n;
+      ksnprintf(buf, size, "%s/%d/%s/%d/%.*hs", sym, err, msg, winerr, n,
+                winmsg);
+    } else {
+      ksnprintf(buf, size, "%s/%d/%s/%d", sym, err, msg, winerr);
+    }
+  }
+  return 0;
+}