Added a dll hello world example program

run following commands to test it:
bazel build --cpu=x64_windows_msvc examples/windows/dll:hello
./bazel-bin/examples/windows/dll/hello

--
Change-Id: I096f6ff66473b1c9980b0aa36ec291f39512dd71
Reviewed-on: https://bazel-review.googlesource.com/#/c/3932
MOS_MIGRATED_REVID=126300284

3 files changed, 68 insertions, 0 deletions

diff --git a/examples/windows/dll/BUILD b/examples/windows/dll/BUILD
new file mode 100644
index 0000000000..2b7e956fc5
--- /dev/null
+++ b/examples/windows/dll/BUILD
@@ -0,0 +1,15 @@
+cc_binary(
+    name = "hellolib.dll",
+    srcs = [
+        "hello-library.cpp",
+    ],
+    linkshared = 1,
+)
+
+cc_binary(
+    name = "hello",
+    srcs = [
+        "hello-world.cpp",
+    ],
+    data = [":hellolib.dll"],
+)
diff --git a/examples/windows/dll/hello-library.cpp b/examples/windows/dll/hello-library.cpp
new file mode 100644
index 0000000000..4cfd7c9c0a
--- /dev/null
+++ b/examples/windows/dll/hello-library.cpp
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <windows.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <time.h>
+
+__declspec(dllexport) char *get_time() {
+  time_t ltime;
+  time(&ltime);
+  return ctime(&ltime);
+}
+
+__declspec(dllexport) void say_hello(char *message) {
+  printf("Hello from dll!\n%s", message);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
diff --git a/examples/windows/dll/hello-world.cpp b/examples/windows/dll/hello-world.cpp
new file mode 100644
index 0000000000..7483e9f070
--- /dev/null
+++ b/examples/windows/dll/hello-world.cpp
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <windows.h>
+typedef char *(__cdecl *GET_TIME_PTR)();
+typedef void(__cdecl *SAY_HELLO_PTR)(char *);
+
+int main() {
+  HINSTANCE hellolib;
+  GET_TIME_PTR get_time;
+  SAY_HELLO_PTR say_hello;
+
+  bool success = FALSE;
+
+  hellolib = LoadLibrary(TEXT("hellolib.dll"));
+
+  if (hellolib != NULL) {
+    get_time = (GET_TIME_PTR)GetProcAddress(hellolib, "get_time");
+    say_hello = (SAY_HELLO_PTR)GetProcAddress(hellolib, "say_hello");
+
+    if (NULL != get_time && NULL != say_hello) {
+      success = TRUE;
+      char *now = get_time();
+      say_hello(now);
+    }
+    FreeLibrary(hellolib);
+  }
+
+  if (!success) printf("Failed to load dll and call functions\n");
+
+  return 0;
+}