GetProcAddress 使用注意事项

Posted 2020-08-03 人最大的荣耀不在于从未失败，而在于每次失败以后都能东山再起

使用?GetProcAddress?Function?时，有以下几点需要特别留意：

1. 第二个参数类型是?LPCSTR，不是?；

2. 用?__declspec(dllexport)，按?C?名称修饰（extern "C"） 导出的函数名，对于?__stdcall?和?__fastcall?调用约定是相同的；对?__cdecl?是不同的（导出的函数名没有前面的下划线）；

3. 即使返回值不是?NULL，也有可能发生错误。当 .def 模块不是连续地从 1 开始编号 ordinal 值，那么，如果用一个无函数对应的 ordinal 值调用?GetProcAddress，就会发生错误，返回一个无效的非?NULL?地址；?

4. 最好用函数名，而不是 ordinal 值调用?GetProcAddress，以避免不同版本 Dll 中某些函数不存在的情况。

注：确认 Dll 的导出函数名，可以用?DUMPBIN /EXPORTS dll_file_name.dll?命令，然后查看?name?列。

[cpp]?view plain?copy

?print?

1. //?The?myPuts?function?writes?a?null-terminated?string?to??
2. //?the?standard?output?device.??
3. ??? ?
4. //?The?export?mechanism?used?here?is?the?__declspec(export)??
5. //?method?supported?by?Microsoft?Visual?Studio,?but?any??
6. //?other?export?method?supported?by?your?development??
7. //?environment?may?be?substituted.??
8. ??? ?
9. ??? ?
10. #include?<windows.h>??
11. ??? ?
12. #define?EOF?(-1)??
13. ??? ?
14. #ifdef?__cplusplus????//?If?used?by?C++?code,???
15. extern?"C"?{??????????//?we?need?to?export?the?C?interface??
16. #endif??
17. ??? ?
18. __declspec(dllexport)?int?__cdecl?myPuts(LPTSTR?lpszMsg)?//?__cdecl?|?__stdcall?|?__fastcall??
19. {??
20. ????DWORD?cchWritten;??
21. ????HANDLE?hStdout;??
22. ????BOOL?fRet;??
23. ??? ?
24. ????//?Get?a?handle?to?the?standard?output?device.??
25. ??? ?
26. ????hStdout?=?GetStdHandle(STD_OUTPUT_HANDLE);??
27. ????if?(INVALID_HANDLE_VALUE?==?hStdout)??
28. ????????return?EOF;??
29. ??? ?
30. ????//?Write?a?null-terminated?string?to?the?standard?output?device.??
31. ??? ?
32. ????while?(*lpszMsg?!=?‘\0‘)??
33. ????{??
34. ????????fRet?=?WriteFile(hStdout,?lpszMsg,?1,?&cchWritten,?NULL);??
35. ????????if(?(FALSE?==?fRet)?||?(1?!=?cchWritten)?)??
36. ????????????return?EOF;??
37. ????????lpszMsg++;??
38. ????}??
39. ??? ?
40. ????return?1;??
41. }??
42. ??? ?
43. #ifdef?__cplusplus??
44. }??
45. #endif??

[cpp]?view plain?copy

?print?

1. //?A?simple?program?that?uses?LoadLibrary?and???
2. //?GetProcAddress?to?access?myPuts?from?Myputs.dll.???
3. ??? ?
4. #include?<stdio.h>???
5. #include?<windows.h>???
6. ??? ?
7. typedef?int?(__cdecl?*MYPROC)(LPTSTR);?//?__cdecl?|?__stdcall?|?__fastcall??
8. ??? ?
9. VOID?main(VOID)???
10. {???
11. ????HINSTANCE?hinstLib;???
12. ????MYPROC?ProcAdd;???
13. ????BOOL?fFreeResult,?fRunTimeLinkSuccess?=?FALSE;???
14. ??? ?
15. ????//?Get?a?handle?to?the?DLL?module.??
16. ??? ?
17. ????hinstLib?=?LoadLibrary(TEXT("bin\\Myputs"));?//?虽然?MSDN?Library?说这里如果??
18. ?????????????????????????????????????????????????//?指定了路径，要用?backslashes?(\)，??
19. ?????????????????????????????????????????????????//?不要用?forward?slashes?(/)，但??
20. ?????????????????????????????????????????????????//?其实用二者都可以。??
21. ?????????????????????????????????????????????????//?注：如果用?\，要用?\\。??
22. ??? ?
23. ????//?If?the?handle?is?valid,?try?to?get?the?function?address.??
24. ??? ?
25. ????if?(hinstLib?!=?NULL)???
26. ????{???
27. ????????ProcAdd?=?(MYPROC)GetProcAddress(hinstLib,?"myPuts");?//?__cdecl???:?myPuts??
28. ??????????????????????????????????????????????????????????????//?__stdcall?:[email protected]??
29. ??????????????????????????????????????????????????????????????//?__fastcall:[email protected]@4??
30. ??? ?
31. ????????//?If?the?function?address?is?valid,?call?the?function.??
32. ??? ?
33. ????????if?(NULL?!=?ProcAdd)???
34. ????????{??
35. ????????????fRunTimeLinkSuccess?=?TRUE;??
36. ????????????(ProcAdd)?(TEXT("Message?via?DLL?function\n"));???
37. ????????}??
38. ??? ?
39. ????????//?Free?the?DLL?module.??
40. ??? ?
41. ????????fFreeResult?=?FreeLibrary(hinstLib);???
42. ????}???
43. ??? ?
44. ????//?If?unable?to?call?the?DLL?function,?use?an?alternative.??
45. ??? ?
46. ????if?(!?fRunTimeLinkSuccess)???
47. ????????printf("Message?via?alternative?method\n");???
48. }??

原文：http://blog.csdn.net/g5dsk/article/details/6680698