From db2f7c48cb30f8fdcb2933aa7d9890b34e0c4e94 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Mon, 25 Sep 2017 18:06:24 +0200 Subject: Win32: simplify loading of DLL functions 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(, , , ......) macro to be used at the beginning of a code block, and the INIT_PROC_ADDR() 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 Signed-off-by: Johannes Schindelin Reviewed-by: Jonathan Nieder Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- 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 0000000000..9e631c8593 --- /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 -- cgit v1.2.1