Improve synchronization

- Fix bugs in kDos2Errno definition
- malloc() should now be thread safe
- Fix bug in rollup.com header generator
- Fix open(O_APPEND) on the New Technology
- Fix select() on the New Technology and test it
- Work towards refactoring i/o for thread safety
- Socket reads and writes on NT now poll for signals
- Work towards i/o completion ports on the New Technology
- Make read() and write() intermittently check for signals
- Blinkenlights keyboard i/o so much better on NT w/ poll()
- You can now poll() files and sockets at the same time on NT
- Fix bug in appendr() that manifests with dlmalloc footers off

test/tool/plinko/plinko_test.c

@@ -20,10 +20,13 @@
 #include "libc/calls/sigbits.h"
 #include "libc/calls/struct/sigaction.h"
 #include "libc/errno.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/macros.internal.h"
 #include "libc/mem/io.h"
 #include "libc/mem/mem.h"
 #include "libc/runtime/runtime.h"
+#include "libc/stdio/stdio.h"
+#include "libc/str/str.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/sig.h"
 #include "libc/testlib/testlib.h"
@@ -61,8 +64,9 @@ void SetUpOnce(void) {
 }
 
 TEST(plinko, worksOrPrintsNiceError) {
-  ssize_t rc;
-  char buf[16], drain[64];
+  size_t n;
+  ssize_t rc, got;
+  char buf[1024], drain[64];
   sigset_t chldmask, savemask;
   int i, pid, fdin, wstatus, pfds[2][2];
   struct sigaction ignore, saveint, savequit, savepipe;
@@ -100,7 +104,8 @@ TEST(plinko, worksOrPrintsNiceError) {
     EXPECT_NE(-1, close(fdin));
   }
   EXPECT_NE(-1, close(pfds[0][1]));
-  EXPECT_NE(-1, read(pfds[1][0], buf, sizeof(buf) - 1));
+  EXPECT_NE(-1, (got = read(pfds[1][0], buf, sizeof(buf) - 1)));
+  EXPECT_NE(0, got);
   while (read(pfds[1][0], drain, sizeof(drain)) > 0) donothing;
   EXPECT_NE(-1, close(pfds[1][0]));
   EXPECT_NE(-1, waitpid(pid, &wstatus, 0));
@@ -115,4 +120,7 @@ TEST(plinko, worksOrPrintsNiceError) {
   EXPECT_EQ(0, sigaction(SIGQUIT, &savequit, 0));
   EXPECT_EQ(0, sigaction(SIGPIPE, &savepipe, 0));
   EXPECT_EQ(0, sigprocmask(SIG_SETMASK, &savemask, 0));
+  if (g_testlib_failed) {
+    kprintf("note: got the following in pipe: %s%n", buf);
+  }
 }