Import Tcl-core 8.6.6 (as of svn r86089)

compat/waitpid.c

@@ -0,0 +1,168 @@
+/*
+ * waitpid.c --
+ *
+ *	This procedure emulates the POSIX waitpid kernel call on BSD systems
+ *	that don't have waitpid but do have wait3. This code is based on a
+ *	prototype version written by Mark Diekhans and Karl Lehenbauer.
+ *
+ * Copyright (c) 1993 The Regents of the University of California.
+ * Copyright (c) 1994 Sun Microsystems, Inc.
+ *
+ * See the file "license.terms" for information on usage and redistribution of
+ * this file, and for a DISCLAIMER OF ALL WARRANTIES.
+ */
+
+#include "tclPort.h"
+
+#ifndef pid_t
+#define pid_t int
+#endif
+
+/*
+ * A linked list of the following structures is used to keep track of
+ * processes for which we received notification from the kernel, but the
+ * application hasn't waited for them yet (this can happen because wait may
+ * not return the process we really want). We save the information here until
+ * the application finally does wait for the process.
+ */
+
+typedef struct WaitInfo {
+    pid_t pid;			/* Pid of process that exited. */
+    WAIT_STATUS_TYPE status;	/* Status returned when child exited or
+				 * suspended. */
+    struct WaitInfo *nextPtr;	/* Next in list of exited processes. */
+} WaitInfo;
+
+static WaitInfo *deadList = NULL;
+				/* First in list of all dead processes. */
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * waitpid --
+ *
+ *	This procedure emulates the functionality of the POSIX waitpid kernel
+ *	call, using the BSD wait3 kernel call. Note: it doesn't emulate
+ *	absolutely all of the waitpid functionality, in that it doesn't
+ *	support pid's of 0 or < -1.
+ *
+ * Results:
+ *	-1 is returned if there is an error in the wait kernel call. Otherwise
+ *	the pid of an exited or suspended process is returned and *statusPtr
+ *	is set to the status value of the process.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+#ifdef waitpid
+#   undef waitpid
+#endif
+
+pid_t
+waitpid(
+    pid_t pid,			/* The pid to wait on. Must be -1 or greater
+				 * than zero. */
+    int *statusPtr,		/* Where to store wait status for the
+				 * process. */
+    int options)		/* OR'ed combination of WNOHANG and
+				 * WUNTRACED. */
+{
+    register WaitInfo *waitPtr, *prevPtr;
+    pid_t result;
+    WAIT_STATUS_TYPE status;
+
+    if ((pid < -1) || (pid == 0)) {
+	errno = EINVAL;
+	return -1;
+    }
+
+    /*
+     * See if there's a suitable process that has already stopped or exited.
+     * If so, remove it from the list of exited processes and return its
+     * information.
+     */
+
+    for (waitPtr = deadList, prevPtr = NULL; waitPtr != NULL;
+	    prevPtr = waitPtr, waitPtr = waitPtr->nextPtr) {
+	if ((pid != waitPtr->pid) && (pid != -1)) {
+	    continue;
+	}
+	if (!(options & WUNTRACED) && (WIFSTOPPED(waitPtr->status))) {
+	    continue;
+	}
+	result = waitPtr->pid;
+	*statusPtr = *((int *) &waitPtr->status);
+	if (prevPtr == NULL) {
+	    deadList = waitPtr->nextPtr;
+	} else {
+	    prevPtr->nextPtr = waitPtr->nextPtr;
+	}
+	ckfree((char *) waitPtr);
+	return result;
+    }
+
+    /*
+     * Wait for any process to stop or exit. If it's an acceptable one then
+     * return it to the caller; otherwise store information about it in the
+     * list of exited processes and try again. On systems that have only wait
+     * but not wait3, there are several situations we can't handle, but we do
+     * the best we can (e.g. can still handle some combinations of options by
+     * invoking wait instead of wait3).
+     */
+
+    while (1) {
+#if NO_WAIT3
+	if (options & WNOHANG) {
+	    return 0;
+	}
+	if (options != 0) {
+	    errno = EINVAL;
+	    return -1;
+	}
+	result = wait(&status);
+#else
+	result = wait3(&status, options, 0);
+#endif
+	if ((result == -1) && (errno == EINTR)) {
+	    continue;
+	}
+	if (result <= 0) {
+	    return result;
+	}
+
+	if ((pid != result) && (pid != -1)) {
+	    goto saveInfo;
+	}
+	if (!(options & WUNTRACED) && (WIFSTOPPED(status))) {
+	    goto saveInfo;
+	}
+	*statusPtr = *((int *) &status);
+	return result;
+
+	/*
+	 * Can't return this info to caller. Save it in the list of stopped or
+	 * exited processes. Tricky point: first check for an existing entry
+	 * for the process and overwrite it if it exists (e.g. a previously
+	 * stopped process might now be dead).
+	 */
+
+    saveInfo:
+	for (waitPtr = deadList; waitPtr != NULL; waitPtr = waitPtr->nextPtr) {
+	    if (waitPtr->pid == result) {
+		waitPtr->status = status;
+		goto waitAgain;
+	    }
+	}
+	waitPtr = (WaitInfo *) ckalloc(sizeof(WaitInfo));
+	waitPtr->pid = result;
+	waitPtr->status = status;
+	waitPtr->nextPtr = deadList;
+	deadList = waitPtr;
+
+    waitAgain:
+	continue;
+    }
+}