Polyfill SIGCHLD on the New Technology

redbean will now cleanup child processes properly. New accounting
information is available too, such as page faults and memory usage. The
way it works is Cosmopolitan Libc samples the process collection on
entry into read() and poll() to see if SIGCHLD needs to be raised.

This change also fixes an issue with chibicc /tmp cleanup. There was
also a regression in MODE=dbg because STL needed ASAN runtime support.

libc/calls/internal.h

@@ -306,6 +306,8 @@ int ioctl_tiocgwinsz_nt(struct Fd *, struct winsize *) hidden;
 │ cosmopolitan § syscalls » windows nt » support                           ─╬─│┼
 ╚────────────────────────────────────────────────────────────────────────────│*/
 
+bool _check_sigchld(void) hidden;
+int __sample_pids(int[hasatleast 64], int64_t[hasatleast 64]) hidden;
 bool isdirectory_nt(const char *) hidden;
 bool isregularfile_nt(const char *) hidden;
 bool issymlink_nt(const char *) hidden;

libc/calls/read-nt.c

@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/bits/bits.h"
 #include "libc/bits/weaken.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/struct/iovec.h"
@@ -46,7 +47,11 @@ textwindows ssize_t sys_read_nt(struct Fd *fd, const struct iovec *iov,
   ssize_t rc;
   uint32_t size;
   size_t i, total;
-  if (weaken(_check_sigwinch) && weaken(_check_sigwinch)(fd)) return eintr();
+  if (cmpxchg(&__interrupted, true, false) ||
+      (weaken(_check_sigchld) && weaken(_check_sigchld)()) ||
+      (weaken(_check_sigwinch) && weaken(_check_sigwinch)(fd))) {
+    return eintr();
+  }
   while (iovlen && !iov[0].iov_len) iov++, iovlen--;
   if (iovlen) {
     for (total = i = 0; i < iovlen; ++i) {

libc/calls/samplepids.c

@@ -0,0 +1,46 @@
+/*-*- 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/calls/internal.h"
+#include "libc/rand/lcg.internal.h"
+
+/**
+ * Returns handles of windows pids being tracked.
+ *
+ * We return 64 at most because Windows can't await on a larger number
+ * of things at the same time. If we have a lot of subprocesses, then we
+ * choose a subgroup to monitor at random.
+ *
+ * @return number of items returned in pids and handles
+ */
+int __sample_pids(int pids[hasatleast 64], int64_t handles[hasatleast 64]) {
+  static uint64_t rando = 1;
+  uint32_t i, j, base, count;
+  base = KnuthLinearCongruentialGenerator(&rando);
+  for (count = i = 0; i < g_fds.n; ++i) {
+    j = (base + i) % g_fds.n;
+    if (g_fds.p[j].kind == kFdProcess) {
+      pids[count] = j;
+      handles[count] = g_fds.p[j].handle;
+      if (++count == 64) {
+        break;
+      }
+    }
+  }
+  return count;
+}

libc/calls/sigchld-nt.c

@@ -0,0 +1,55 @@
+/*-*- 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/calls/internal.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/calls/struct/siginfo.h"
+#include "libc/calls/typedef/sigaction_f.h"
+#include "libc/nt/enum/status.h"
+#include "libc/nt/enum/wait.h"
+#include "libc/nt/runtime.h"
+#include "libc/nt/synchronization.h"
+#include "libc/runtime/runtime.h"
+#include "libc/sysv/consts/sicode.h"
+#include "libc/sysv/consts/sig.h"
+
+/**
+ * Checks to see if SIGCHLD should be raised on Windows.
+ * @return true if a signal was raised
+ */
+bool _check_sigchld(void) {
+  siginfo_t si;
+  int pids[64];
+  uint32_t i, n;
+  int64_t handles[64];
+  if (__sighandrvas[SIGCHLD] < kSigactionMinRva) return false;
+  if (!(n = __sample_pids(pids, handles))) return false;
+  i = WaitForMultipleObjects(n, handles, false, 0);
+  if (i == kNtWaitTimeout) return false;
+  if (i == kNtWaitFailed) {
+    STRACE("%s failed %u", "WaitForMultipleObjects", GetLastError());
+    return false;
+  }
+  STRACE("SIGCHLD fd=%d handle=%ld", pids[i], handles[i]);
+  bzero(&si, sizeof(si));
+  si.si_signo = SIGCHLD;
+  si.si_code = CLD_EXITED;
+  si.si_pid = pids[i];
+  ((sigaction_f)(_base + __sighandrvas[SIGCHLD]))(SIGCHLD, &si, 0);
+  return true;
+}

libc/calls/sigwinch-nt.c

@@ -23,6 +23,7 @@
 #include "libc/errno.h"
 #include "libc/nt/struct/consolescreenbufferinfoex.h"
 #include "libc/str/str.h"
+#include "libc/sysv/consts/sig.h"
 
 static struct winsize __ws;
 
@@ -42,6 +43,7 @@ textwindows bool _check_sigwinch(struct Fd *fd) {
                  ws.ws_col, ws.ws_row);
           if (__sighandrvas[SIGWINCH] >= kSigactionMinRva) {
             bzero(&si, sizeof(si));
+            si.si_signo = SIGWINCH;
             ((sigaction_f)(_base + __sighandrvas[SIGWINCH]))(SIGWINCH, &si, 0);
             return true;
           }

libc/calls/wait4-nt.c

@@ -33,6 +33,7 @@
 #include "libc/nt/struct/filetime.h"
 #include "libc/nt/struct/processmemorycounters.h"
 #include "libc/nt/synchronization.h"
+#include "libc/rand/lcg.internal.h"
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/o.h"
@@ -45,10 +46,14 @@ textwindows int sys_wait4_nt(int pid, int *opt_out_wstatus, int options,
   int64_t handle;
   int64_t handles[64];
   uint32_t dwExitCode;
-  uint32_t i, count, timeout;
+  uint32_t i, j, base, count, timeout;
   struct NtProcessMemoryCountersEx memcount;
   struct NtFileTime createfiletime, exitfiletime, kernelfiletime, userfiletime;
-  if (pid != -1) {
+  if (pid != -1 && pid != 0) {
+    if (pid < 0) {
+      /* XXX: this is sloppy */
+      pid = -pid;
+    }
     if (!__isfdkind(pid, kFdProcess)) {
       /* XXX: this is sloppy (see fork-nt.c) */
       if (!__isfdopen(pid) &&
@@ -70,16 +75,8 @@ textwindows int sys_wait4_nt(int pid, int *opt_out_wstatus, int options,
     pids[0] = pid;
     count = 1;
   } else {
-    for (count = 0, i = g_fds.n; i--;) {
-      if (g_fds.p[i].kind == kFdProcess) {
-        pids[count] = i;
-        handles[count] = g_fds.p[i].handle;
-        if (++count == ARRAYLEN(handles)) break;
-      }
-    }
-    if (!count) {
-      return echild();
-    }
+    count = __sample_pids(pids, handles);
+    if (!count) return echild();
   }
   for (;;) {
     dwExitCode = kNtStillActive;