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/calls/kill-nt.c

@@ -20,18 +20,21 @@
 #include "libc/calls/getconsolectrlevent.internal.h"
 #include "libc/calls/internal.h"
 #include "libc/dce.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/console.h"
 #include "libc/nt/enum/ctrlevent.h"
 #include "libc/nt/enum/processaccess.h"
+#include "libc/nt/enum/th32cs.h"
 #include "libc/nt/errors.h"
 #include "libc/nt/process.h"
 #include "libc/nt/runtime.h"
+#include "libc/nt/struct/processentry32.h"
 #include "libc/sysv/errfuns.h"
 
 textwindows int sys_kill_nt(int pid, int sig) {
   bool32 ok;
-  int64_t handle;
+  int64_t h;
   int event, ntpid;
 
   // is killing everything except init really worth supporting?
@@ -68,20 +71,37 @@ textwindows int sys_kill_nt(int pid, int sig) {
     }
   }
 
-  // XXX: Is this a cosmo pid that was returned by fork_nt?
+  // is this a cosmo pid that was returned by fork?
   if (__isfdkind(pid, kFdProcess)) {
+    // since windows can't execve we need to kill the grandchildren
+    // TODO(jart): should we just kill the whole tree too? there's
+    //             no obvious way to tell if it's the execve shell
+    int64_t hSnap, hProc, hChildProc;
+    struct NtProcessEntry32 pe = {.dwSize = sizeof(struct NtProcessEntry32)};
+    ntpid = GetProcessId(g_fds.p[pid].handle);
+    hSnap = CreateToolhelp32Snapshot(kNtTh32csSnapprocess, 0);
+    if (Process32First(hSnap, &pe)) {
+      do {
+        if (pe.th32ParentProcessID == ntpid) {
+          if ((h = OpenProcess(kNtProcessTerminate, false, pe.th32ProcessID))) {
+            TerminateProcess(h, 128 + sig);
+            CloseHandle(h);
+          }
+        }
+      } while (Process32Next(hSnap, &pe));
+    }
     ok = TerminateProcess(g_fds.p[pid].handle, 128 + sig);
     if (!ok && GetLastError() == kNtErrorAccessDenied) ok = true;
     return 0;
   }
 
   // XXX: Is this a raw new technology pid? Because that's messy.
-  if ((handle = OpenProcess(kNtProcessTerminate, false, pid))) {
-    ok = TerminateProcess(handle, 128 + sig);
+  if ((h = OpenProcess(kNtProcessTerminate, false, pid))) {
+    ok = TerminateProcess(h, 128 + sig);
     if (!ok && GetLastError() == kNtErrorAccessDenied) {
       ok = true;  // cargo culting other codebases here
     }
-    CloseHandle(handle);
+    CloseHandle(h);
     return 0;
   } else {
     return -1;

libc/calls/sigaltstack.c

@@ -57,8 +57,9 @@ static void sigaltstack2linux(struct sigaltstack *linux,
  *     struct sigaction sa;
  *     struct sigaltstack ss;
  *     ss.ss_flags = 0;
- *     ss.ss_size = SIGSTKSZ;
- *     ss.ss_sp = malloc(ss.ss_size);
+ *     ss.ss_size = GetStackSize();
+ *     ss.ss_sp = mmap(0, GetStackSize(), PROT_READ | PROT_WRITE,
+ *                     MAP_STACK | MAP_ANONYMOUS, -1, 0);
  *     sa.sa_flags = SA_ONSTACK;
  *     sa.sa_handler = OnStackOverflow;
  *     __cxa_atexit(free, ss[0].ss_sp, 0);
@@ -66,6 +67,11 @@ static void sigaltstack2linux(struct sigaltstack *linux,
  *     sigaltstack(&ss, 0);
  *     sigaction(SIGSEGV, &sa, 0);
  *
+ * It's strongly recommended that you allocate a stack with the same
+ * size as GetStackSize() and that it have GetStackSize() alignment.
+ * Otherwise some of your runtime support code (e.g. ftrace stack use
+ * logging, kprintf() memory safety) won't be able to work as well.
+ *
  * @param neu if non-null will install new signal alt stack
  * @param old if non-null will receive current signal alt stack
  * @return 0 on success, or -1 w/ errno

libc/calls/wincrash.c

@@ -35,6 +35,7 @@ privileged unsigned __wincrash(struct NtExceptionPointers *ep) {
   int sig, code;
   ucontext_t ctx;
   STRACE("__wincrash");
+
   switch (ep->ExceptionRecord->ExceptionCode) {
     case kNtSignalBreakpoint:
       code = TRAP_BRKPT;