posix: patch to implement get_pid function

patch to implement get_pid function

Signed-off-by: Jai Arora <infolinesoni@gmail.com>

include/zephyr/posix/posix_types.h

@@ -21,6 +21,8 @@
 extern "C" {
 #endif
 
+typedef int pid_t;
+
 #ifndef __useconds_t_defined
 typedef unsigned long useconds_t;
 #endif

include/zephyr/posix/unistd.h

@@ -51,6 +51,7 @@ extern char *optarg;
 extern int opterr, optind, optopt;
 #endif
 
+pid_t getpid(void);
 unsigned sleep(unsigned int seconds);
 int usleep(useconds_t useconds);
 

lib/posix/pthread.c

@@ -15,6 +15,7 @@
 #include <zephyr/logging/log.h>
 #include <zephyr/sys/atomic.h>
 #include <zephyr/posix/pthread.h>
+#include <zephyr/posix/unistd.h>
 #include <zephyr/sys/slist.h>
 #include <zephyr/sys/util.h>
 
@@ -158,6 +159,22 @@ int pthread_equal(pthread_t pt1, pthread_t pt2)
 	return (pt1 == pt2);
 }
 
+pid_t getpid(void)
+{
+	/*
+	 * To maintain compatibility with some other POSIX operating systems,
+	 * a PID of zero is used to indicate that the process exists in another namespace.
+	 * PID zero is also used by the scheduler in some cases.
+	 * PID one is usually reserved for the init process.
+	 * Also note, that negative PIDs may be used by kill()
+	 * to send signals to process groups in some implementations.
+	 *
+	 * At the moment, getpid just returns an arbitrary number >= 2
+	 */
+
+	return 42;
+}
+
 static inline void __z_pthread_cleanup_init(struct __pthread_cleanup *c, void (*routine)(void *arg),
 					    void *arg)
 {