mingw: factor out lazy-loading functions from .dll files

This code is very useful and needed also in compat/poll/poll.c, so let's
factor out those macros and functions into their own header file.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

compat/win32.h

@@ -6,6 +6,8 @@
 #include <windows.h>
 #endif
 
+#include "compat/win32/lazyload.h"
+
 static inline int file_attr_to_st_mode (DWORD attr, DWORD tag)
 {
 	int fMode = S_IREAD;
@@ -40,42 +42,4 @@ static inline int get_file_attr(const char *fname, WIN32_FILE_ATTRIBUTE_DATA *fd
 	}
 }
 
-/* simplify loading of DLL functions */
-
-struct proc_addr {
-	const char *const dll;
-	const char *const function;
-	FARPROC pfunction;
-	unsigned initialized : 1;
-};
-
-/* Declares a function to be loaded dynamically from a DLL. */
-#define DECLARE_PROC_ADDR(dll, rettype, function, ...) \
-	static struct proc_addr proc_addr_##function = \
-	{ #dll, #function, NULL, 0 }; \
-	static rettype (WINAPI *function)(__VA_ARGS__)
-
-/*
- * Loads a function from a DLL (once-only).
- * Returns non-NULL function pointer on success.
- * Returns NULL + errno == ENOSYS on failure.
- */
-#define INIT_PROC_ADDR(function) (function = get_proc_addr(&proc_addr_##function))
-
-static inline void *get_proc_addr(struct proc_addr *proc)
-{
-	/* only do this once */
-	if (!proc->initialized) {
-		HANDLE hnd;
-		proc->initialized = 1;
-		hnd = LoadLibraryA(proc->dll);
-		if (hnd)
-			proc->pfunction = GetProcAddress(hnd, proc->function);
-	}
-	/* set ENOSYS if DLL or function was not found */
-	if (!proc->pfunction)
-		errno = ENOSYS;
-	return proc->pfunction;
-}
-
 #endif

compat/win32/lazyload.h

@@ -0,0 +1,42 @@
+#ifndef LAZYLOAD_H
+#define LAZYLOAD_H
+
+/* simplify loading of DLL functions */
+
+struct proc_addr {
+	const char *const dll;
+	const char *const function;
+	FARPROC pfunction;
+	unsigned initialized : 1;
+};
+
+/* Declares a function to be loaded dynamically from a DLL. */
+#define DECLARE_PROC_ADDR(dll, rettype, function, ...) \
+	static struct proc_addr proc_addr_##function = \
+	{ #dll, #function, NULL, 0 }; \
+	static rettype (WINAPI *function)(__VA_ARGS__)
+
+/*
+ * Loads a function from a DLL (once-only).
+ * Returns non-NULL function pointer on success.
+ * Returns NULL + errno == ENOSYS on failure.
+ */
+#define INIT_PROC_ADDR(function) (function = get_proc_addr(&proc_addr_##function))
+
+static inline void *get_proc_addr(struct proc_addr *proc)
+{
+	/* only do this once */
+	if (!proc->initialized) {
+		HANDLE hnd;
+		proc->initialized = 1;
+		hnd = LoadLibraryA(proc->dll);
+		if (hnd)
+			proc->pfunction = GetProcAddress(hnd, proc->function);
+	}
+	/* set ENOSYS if DLL or function was not found */
+	if (!proc->pfunction)
+		errno = ENOSYS;
+	return proc->pfunction;
+}
+
+#endif