Dynamic loading of DLL functions is duplicated in several places in Git
for Windows' source code.
This patch adds a pair of macros to simplify the process: the
DECLARE_PROC_ADDR(<dll>, <return-type>, <function-name>,
...<function-parameter-types>...) macro to be used at the beginning of a
code block, and the INIT_PROC_ADDR(<function-name>) macro to call before
using the declared function. The return value of the INIT_PROC_ADDR()
call has to be checked; If it is NULL, the function was not found in the
specified DLL.
Example:
DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateHardLinkW,
LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
if (!INIT_PROC_ADDR(CreateHardLinkW))
return error("Could not find CreateHardLinkW() function";
if (!CreateHardLinkW(source, target, NULL))
return error("could not create hardlink from %S to %S",
source, target);
return 0;
Signed-off-by: Karsten Blees <bl...@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schinde...@gmx.de>
Reviewed-by: Jonathan Nieder <jrnie...@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schinde...@gmx.de>
---
compat/win32/lazyload.h | 57 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 57 insertions(+)
create mode 100644 compat/win32/lazyload.h
diff --git a/compat/win32/lazyload.h b/compat/win32/lazyload.h
new file mode 100644
index 00000000000..9e631c8593f
--- /dev/null
+++ b/compat/win32/lazyload.h
@@ -0,0 +1,57 @@
+#ifndef LAZYLOAD_H
+#define LAZYLOAD_H
+
+/*
+ * A pair of macros to simplify loading of DLL functions. Example:
+ *
+ * DECLARE_PROC_ADDR(kernel32.dll, BOOL, CreateHardLinkW,
+ * LPCWSTR, LPCWSTR, LPSECURITY_ATTRIBUTES);
+ *
+ * if (!INIT_PROC_ADDR(CreateHardLinkW))
+ * return error("Could not find CreateHardLinkW() function";
+ *
+ * if (!CreateHardLinkW(source, target, NULL))
+ * return error("could not create hardlink from %S to %S",
+ * source, target);
+ */
+
+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.
+ * This function is not thread-safe.
+ */
+#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 = LoadLibraryExA(proc->dll, NULL,
+ LOAD_LIBRARY_SEARCH_SYSTEM32);
+ 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
--
2.14.1.windows.1.1024.gf2dea585d74.dirty
