🐛 fix error return value after call waitpid

src/natives/subprocess.cpp

@@ -169,6 +169,11 @@ var builtin_subprocess_active(context* ctx, gc* ngc) {
     int status;
     pid_t result = waitpid(pid, &status, WNOHANG);
 
+    // this means the child process is returned
+    if (result==pid) {
+        obj.ghost().get<subprocess>()->status = status;
+    } 
+
     return result==0? one:zero;
 #endif
 }
@@ -192,21 +197,31 @@ var builtin_subprocess_terminate(context* ctx, gc* ngc) {
 
     CloseHandle(pi->hProcess);
     CloseHandle(pi->hThread);
+
+    return var::num(res);
 #else
     auto pid = obj.ghost().get<subprocess>()->pid;
 
     int status;
     pid_t result = waitpid(pid, &status, WNOHANG);
 
-    // child process running
-    if (result==0) {
-        kill(pid, SIGTERM);
+    if (result<0) {
+        auto pstat = obj.ghost().get<subprocess>()->status;
+        // if pstat is not 0, means child process already exited
+        auto res = WIFEXITED(pstat)? WEXITSTATUS(pstat):-1;
+        return var::num(res);
     }
 
-    auto res = WIFEXITED(status)? WEXITSTATUS(status):-1;
-#endif
+    // child process is still running
+    if (result==0) {
+        kill(pid, SIGTERM);
+        return var::num(-1);
+    }
 
+    // child process exited when calling the waitpid above
+    auto res = WIFEXITED(status)? WEXITSTATUS(status):-1;
     return var::num(res);
+#endif
 }
 
 nasal_builtin_table subprocess_native[] = {

src/natives/subprocess.h

@@ -17,6 +17,7 @@ namespace nasal {
 struct subprocess {
 #ifndef WIN32
     pid_t pid;
+    int status = 0;
 #else
     STARTUPINFOW si;
     PROCESS_INFORMATION pi;

test/watchdog.nas

@@ -65,7 +65,7 @@ while(1) {
         modified_time = latest_modified_time;
         println(os_time(), modified_hd(), filename);
 
-        var cmd = (os.platform()=="windows"?"":"./") ~ "nasal " ~ filename;
+        var cmd = "nasal " ~ filename;
         foreach(var i; args) {
             cmd ~= " " ~ i;
         }