Hello!
Im trying to load a function from a DLL only, however GetProcAddress() returns NULL.
I just wanted to try loading it in another way than what casey did with all that:
#define -> typedef thingy... :)
Person.h
Person.cpp
main.cpp
b.bat
Im trying to load a function from a DLL only, however GetProcAddress() returns NULL.
I just wanted to try loading it in another way than what casey did with all that:
#define -> typedef thingy... :)
Person.h
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | #include <stdio.h> struct Person { char *name; int age; }; extern "C" void printAge(Person *p); typedef void PFNPRINTAGE(Person *p); void printAgeSTUB(Person *p) { } |
Person.cpp
1 2 3 4 5 6 7 | #include "Person.h" extern "C" void printAge(Person *p) { printf("\nAge of Person: %d\n", p->age); } |
main.cpp
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | #include <windows.h> #include <stdlib.h> #include <string.h> #include "Person.h" int main() { Person p1 = {}; p1.age = 11; HMODULE PersonDLL = LoadLibrary("Person.dll"); PFNPRINTAGE *printAge = printAgeSTUB; if(PersonDLL) { printAge = (PFNPRINTAGE*)GetProcAddress(PersonDLL, "printAge"); DWORD err = GetLastError(); printAge(&p1); } FreeLibrary(PersonDLL); return 0; |
b.bat
1 2 3 4 5 6 7 8 9 10 11 12 | @echo off IF NOT EXIST ..\build mkdir ..\build pushd ..\build cl -nologo -Zi ..\src\Person.cpp -LD cl -nologo -Zi ..\src\playGround.cpp /link -incremental:no user32.lib kernel32.lib winmm.lib gdi32.lib popd del *.cpp~ *.bat~ *.un~ *.txt~ |
Edited by C_Worm
on
Reason: Initial post
You did not instruct linker to export function from dll file.
You can do in two ways. One with compiler directive:
Another with linker argument:
You can verify if DLL has this symbol exported by using dumpbin.exe utility:
If it does not show your "printAge", that means something was not done properly.
You can do in two ways. One with compiler directive:
1 2 3 | extern "C" __declspec(dllexport) void printAge(Person *p); |
Another with linker argument:
1 | cl.exe ... /link /export:printAge |
You can verify if DLL has this symbol exported by using dumpbin.exe utility:
1 | dumpbin /exports Person.dll |
If it does not show your "printAge", that means something was not done properly.
mmozeiko
You did not instruct linker to export function from dll file.
You can do in two ways. One with compiler directive:
Another with linker argument:
You can verify if DLL has this symbol exported by using dumpbin.exe utility:
If it does not show your "printAge", that means something was not done properly.
So you MUST create a .lib file aswell, else you can't load function from DLL??
__declspec(dllexport) seems to create the .lib file
You don't need to use .lib if you are loading .dll at runtime. Linker always creates it if you have exported symbols. So you can use .lib to link to dll at link time, if you want. It's your choice what to do.
Edited by Mārtiņš Možeiko
on