From 41b9b4b3bf65af29304bf732fd6e643edf3fcd49 Mon Sep 17 00:00:00 2001
From: Allen Webster <yoyo4thdimention@gmail.com>
Date: Tue, 23 Apr 2024 11:50:47 -0700
Subject: [PATCH] win32_load_time example

---
 .gitignore                     |  1 +
 win32_load_time/build.bat      | 26 +++++++++++++++++++++++
 win32_load_time/win32_base.c   | 11 ++++++++++
 win32_load_time/win32_main.c   | 38 ++++++++++++++++++++++++++++++++++
 win32_load_time/win32_plugin.c | 17 +++++++++++++++
 5 files changed, 93 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 win32_load_time/build.bat
 create mode 100644 win32_load_time/win32_base.c
 create mode 100644 win32_load_time/win32_main.c
 create mode 100644 win32_load_time/win32_plugin.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..07ed706
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+build/*
\ No newline at end of file
diff --git a/win32_load_time/build.bat b/win32_load_time/build.bat
new file mode 100644
index 0000000..d7e5898
--- /dev/null
+++ b/win32_load_time/build.bat
@@ -0,0 +1,26 @@
+@echo off
+
+SET src=%cd%
+
+cd ..
+if not exist "build\" mkdir build
+cd build
+
+REM: ## The arrangement of this build ##
+REM:  The "base layer" must be built and shared by all dynamic components.
+REM:  In this example the the base layer is linked via load-time linking with the other modules.
+REM:  The "plugin" is loaded at run-time.
+
+
+
+REM: Build the base layer as a .dll (also produces load-time linking data in win32_base.lib)
+cl /nologo /Zi /LD %src%\win32_base.c
+
+
+REM: Build the executable; provide the base layer's load-time linking data via win32_base.lib
+cl /nologo /Zi %src%\win32_main.c win32_base.lib
+
+
+REM: Build the plugin as a .dll; provide the base layer's load-time linking data via win32_base.lib
+cl /nologo /Zi /LD %src%\win32_plugin.c win32_base.lib
+
diff --git a/win32_load_time/win32_base.c b/win32_load_time/win32_base.c
new file mode 100644
index 0000000..01f2446
--- /dev/null
+++ b/win32_load_time/win32_base.c
@@ -0,0 +1,11 @@
+// declare base_func; mark it as an exported symbol
+__declspec(dllexport) void base_func(void);
+
+// define base_func
+#include <stdio.h>
+int x = 0;
+__declspec(dllexport) void
+base_func(void){
+  printf("x = %d\n", x);
+  x += 1;
+}
diff --git a/win32_load_time/win32_main.c b/win32_load_time/win32_main.c
new file mode 100644
index 0000000..5f19acc
--- /dev/null
+++ b/win32_load_time/win32_main.c
@@ -0,0 +1,38 @@
+// declare base_func; mark it as a load-time imported symbol
+__declspec(dllimport) void base_func(void);
+
+
+// setup plugin_func as a function pointer so that it can be linked at run time
+typedef void PLUGIN_Func(void);
+PLUGIN_Func *plugin_func = 0;
+
+
+// need to include for LoadLibraryA/LoadLibraryW and GetProcAddress
+#include <Windows.h>
+
+// helper macro for GetProcAddress that handles the casting of function pointers
+#define GET_PROC(var,mod,name) *((FARPROC*)(&(var))) = GetProcAddress((mod),(name))
+
+
+int main(){
+  
+  // functions linked by load-time linking can be called directly without further setup
+  base_func();
+  
+  
+  // to call a function with run-time linking, we must manually load and link it
+  HMODULE module = LoadLibraryA("win32_plugin.dll");
+  if (module != 0){
+    GET_PROC(plugin_func, module, "plugin_func");
+  }
+  
+  
+  // calls to plugin_func only work after the "plugin" loaded successfully
+  if (plugin_func != 0){
+    plugin_func();
+  }
+  
+  
+  // demonstration: the data structures contained in the 'base' are not duplicated in each binary
+  base_func();
+}
diff --git a/win32_load_time/win32_plugin.c b/win32_load_time/win32_plugin.c
new file mode 100644
index 0000000..2117f48
--- /dev/null
+++ b/win32_load_time/win32_plugin.c
@@ -0,0 +1,17 @@
+// declare base_func; mark it as a load-time imported symbol
+__declspec(dllimport) void base_func(void);
+
+// declare plugin_func; mark it as an exported symbol
+__declspec(dllexport) void plugin_func(void);
+
+// define plugin_func
+#include <stdio.h>
+__declspec(dllexport) void
+plugin_func(void){
+  printf("provided by plugin: {\n");
+  printf(" ");
+  base_func();
+  printf(" ");
+  base_func();
+  printf("}\n");
+}