Visual Studio C++ link with psapi.lib - c

Question

I have written a C Program which calls the function, GetModuleInformation() which is defined in psapi.h
I am using Microsoft Visual Studio C++ command line compiler (cl.exe) for compiling and linking the program.
I have included the psapi.h header file:
#include <psapi.h>
when I try to compile using:
cl program.c
It generates the object file, however fails during the linking stage with the error:
program.obj : error LNK2019: unresolved external symbol _GetModuleInformation#16 ref
erenced in function _main
program.exe : fatal error LNK1120: 1 unresolved externalsprogram.obj : error LNK2019: unresolved external symbol _GetModuleInformation#16 ref
I also place the psapi.lib file in the same folder where the source code file (program.c) is placed, however even then I get the same error message as above.
How do I successfully link it using the command line compiler (cl.exe)?

Answer 1

Method 1
If you want to compile from the command line with cl.exe you can use the /link option to specify linker options :
cl /TC program.c /link psapi.lib
Method 2
The following pragma directive causes the linker to search in your source file for the psapi.lib library while linking .
#pragma comment( lib, "psapi.lib" )
Possible reason for your errors can be, if psapi.lib is missing in a list of additional libraries of linker.
To resolve this, use the following /LIBPATH option :
cl /TC program.c /link Psapi.Lib /LIBPATH:C:\MyLibFolder\
Where C:\MyLibFolder specifies a path to the folder, that contains your psapi.lib .
Also, you can try to set the proper /SUBSYSTEM option .
For a Console application use :
/SUBSYSTEM:CONSOLE
Solution to similar problem here .
Example on using the GetModuleInformation function :
#include <windows.h>
#include <stdio.h>
#include <psapi.h>
#pragma comment( lib, "psapi.lib" )
int main(void)
{
MODULEINFO minfo = {0};
GetModuleInformation( GetCurrentProcess(), GetModuleHandle( "psapi.dll" ), &minfo, sizeof(minfo) );
/* printf("%X", minfo.lpBaseOfDll); /* The load address of the module */
return 0;
}
The code has been tested on Windows 7 and XP .
The output from linking session is :
program.c
/out:program.exe
psapi.lib
/LIBPATH:C:\MyLibFolder\
/SUBSYSTEM:CONSOLE
/VERBOSE
program.obj
Starting pass 1
Processed /DEFAULTLIB:uuid.lib
Processed /DEFAULTLIB:LIBCMT
Processed /DEFAULTLIB:OLDNAMES
Searching libraries
Searching C:\MyLibFolder\psapi.lib:
Found _GetModuleInformation#16
Referenced in program.obj
Loaded psapi.lib(PSAPI.DLL)
Found __IMPORT_DESCRIPTOR_PSAPI
Referenced in psapi.lib(PSAPI.DLL)
Loaded psapi.lib(PSAPI.DLL)
Found __NULL_IMPORT_DESCRIPTOR
Referenced in psapi.lib(PSAPI.DLL)
Loaded psapi.lib(PSAPI.DLL)
...
If vsvars32.bat and all appropriate environment variables in your Visual Studio are set correctly the above linker options will produce a valid executable(.exe) file.