Win32: simplify loading of DLL functions

Dynamic loading of DLL functions is duplicated in several places.

Add a set of macros to simplify the process.

Signed-off-by: Karsten Blees <[email protected]>

Author: kblees

compat/mingw.c

@@ -2017,23 +2017,16 @@ static const char *make_backslash_path(const char *path)
 void mingw_open_html(const char *unixpath)
 {
 	const char *htmlpath = make_backslash_path(unixpath);
-	typedef HINSTANCE (WINAPI *T)(HWND, const char *,
-			const char *, const char *, const char *, INT);
-	T ShellExecute;
-	HMODULE shell32;
 	int r;
+	DECLARE_PROC_ADDR(shell32.dll, HINSTANCE, ShellExecuteA,
+			HWND, LPCSTR, LPCSTR, LPCSTR, LPCSTR, INT);
 
-	shell32 = LoadLibrary("shell32.dll");
-	if (!shell32)
+	if (!INIT_PROC_ADDR(ShellExecuteA))
 		die("cannot load shell32.dll");
-	ShellExecute = (T)GetProcAddress(shell32, "ShellExecuteA");
-	if (!ShellExecute)
-		die("cannot run browser");
 
 	printf("Launching default browser to display HTML ...\n");
-	r = HCAST(int, ShellExecute(NULL, "open", htmlpath,
+	r = HCAST(int, ShellExecuteA(NULL, "open", htmlpath,
 				NULL, "\\", SW_SHOWNORMAL));
-	FreeLibrary(shell32);
 	/* see the MSDN documentation referring to the result codes here */
 	if (r <= 32) {
 		die("failed to launch browser for %.*s", MAX_PATH, unixpath);
@@ -2042,24 +2035,18 @@ void mingw_open_html(const char *unixpath)
 
 int link(const char *oldpath, const char *newpath)
 {
-	typedef BOOL (WINAPI *T)(LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
-	static T create_hard_link = NULL;
+	DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateHardLinkW,
+			LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
 	wchar_t woldpath[MAX_LONG_PATH], wnewpath[MAX_LONG_PATH];
+
+	if (!INIT_PROC_ADDR(CreateHardLinkW))
+		return -1;
+
 	if (xutftowcs_long_path(woldpath, oldpath) < 0 ||
 	    xutftowcs_long_path(wnewpath, newpath) < 0)
 		return -1;
 
-	if (!create_hard_link) {
-		create_hard_link = (T) GetProcAddress(
-			GetModuleHandle("kernel32.dll"), "CreateHardLinkW");
-		if (!create_hard_link)
-			create_hard_link = (T)-1;
-	}
-	if (create_hard_link == (T)-1) {
-		errno = ENOSYS;
-		return -1;
-	}
-	if (!create_hard_link(wnewpath, woldpath, NULL)) {
+	if (!CreateHardLinkW(wnewpath, woldpath, NULL)) {
 		errno = err_win_to_posix(GetLastError());
 		return -1;
 	}

compat/win32.h

@@ -40,4 +40,41 @@ 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) {
+		proc->initialized = 1;
+		HANDLE 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/winansi.c

@@ -6,6 +6,7 @@
 #include "../git-compat-util.h"
 #include <wingdi.h>
 #include <winreg.h>
+#include "win32.h"
 
 /*
  ANSI codes used by git: m, K
@@ -35,26 +36,21 @@ typedef struct _CONSOLE_FONT_INFOEX {
 #endif
 #endif
 
-typedef BOOL (WINAPI *PGETCURRENTCONSOLEFONTEX)(HANDLE, BOOL,
-		PCONSOLE_FONT_INFOEX);
-
 static void warn_if_raster_font(void)
 {
 	DWORD fontFamily = 0;
-	PGETCURRENTCONSOLEFONTEX pGetCurrentConsoleFontEx;
+	DECLARE_PROC_ADDR(kernel32.dll, BOOL, GetCurrentConsoleFontEx,
+			HANDLE, BOOL, PCONSOLE_FONT_INFOEX);
 
 	/* don't bother if output was ascii only */
 	if (!non_ascii_used)
 		return;
 
 	/* GetCurrentConsoleFontEx is available since Vista */
-	pGetCurrentConsoleFontEx = (PGETCURRENTCONSOLEFONTEX) GetProcAddress(
-			GetModuleHandle("kernel32.dll"),
-			"GetCurrentConsoleFontEx");
-	if (pGetCurrentConsoleFontEx) {
+	if (INIT_PROC_ADDR(GetCurrentConsoleFontEx)) {
 		CONSOLE_FONT_INFOEX cfi;
 		cfi.cbSize = sizeof(cfi);
-		if (pGetCurrentConsoleFontEx(console, 0, &cfi))
+		if (GetCurrentConsoleFontEx(console, 0, &cfi))
 			fontFamily = cfi.FontFamily;
 	} else {
 		/* pre-Vista: check default console font in registry */