add integration test

Author: SchrodingerZhu

libc/test/integration/src/unistd/CMakeLists.txt

@@ -31,6 +31,10 @@ add_integration_test(
     libc.src.sys.wait.wait4
     libc.src.sys.wait.waitpid
     libc.src.unistd.fork
+    libc.src.unistd.getpid
+    libc.src.unistd.gettid
+    libc.src.stdlib.exit
+    libc.include.sys_syscall
 )
 
 if((${LIBC_TARGET_OS} STREQUAL "linux") AND (${LIBC_TARGET_ARCHITECTURE_IS_X86}))

libc/test/integration/src/unistd/fork_test.cpp

@@ -6,17 +6,21 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/__support/OSUtil/syscall.h"
 #include "src/pthread/pthread_atfork.h"
 #include "src/signal/raise.h"
+#include "src/stdlib/exit.h"
 #include "src/sys/wait/wait.h"
 #include "src/sys/wait/wait4.h"
 #include "src/sys/wait/waitpid.h"
 #include "src/unistd/fork.h"
-
+#include "src/unistd/getpid.h"
+#include "src/unistd/gettid.h"
 #include "test/IntegrationTest/test.h"
 
 #include <errno.h>
 #include <signal.h>
+#include <sys/syscall.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
@@ -140,7 +144,25 @@ void fork_with_atfork_callbacks() {
   ASSERT_NE(child, DONE);
 }
 
+void fork_pid_tid_test() {
+  pid_t pid = fork();
+  ASSERT_TRUE(pid >= 0);
+  ASSERT_EQ(LIBC_NAMESPACE::gettid(),
+            LIBC_NAMESPACE::syscall_impl<pid_t>(SYS_gettid));
+  ASSERT_EQ(LIBC_NAMESPACE::getpid(),
+            LIBC_NAMESPACE::syscall_impl<pid_t>(SYS_getpid));
+
+  if (pid == 0) {
+    LIBC_NAMESPACE::exit(0);
+  } else {
+    int status;
+    LIBC_NAMESPACE::waitpid(pid, &status, 0);
+    ASSERT_EQ(status, 0);
+  }
+}
+
 TEST_MAIN(int argc, char **argv, char **envp) {
+  fork_pid_tid_test();
   fork_and_wait_normal_exit();
   fork_and_wait4_normal_exit();
   fork_and_waitpid_normal_exit();