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Traversing the module list

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This code example retrieves a list of modules for a specified process (by default, the current process). The ListProcessModules function takes a snapshot of the modules associated with a given process. To do that, it uses the CreateToolhelp32Snapshot function, and then it walks through the list using the Module32First and Module32Next functions. The dwPID parameter of ListProcessModules identifies the process for which modules are to be enumerated, and that's usually obtained by calling CreateToolhelp32Snapshot to enumerate the processes running on the system. See Taking a snapshot and viewing processes for a simple console application that uses this function.

A simple error-reporting function, printError, displays the reason for any failures (which typically result from security restrictions).

To follow along with the code example, use Visual Studio to create a new project from the C++ Console App project template, and add the code below to it.

#include <windows.h> 
#include <tlhelp32.h> 
#include <tchar.h> 

//  Forward declarations: 
BOOL ListProcessModules(DWORD dwPID ); 
void printError(TCHAR const* msg ); 
 
int main( void )
{
  ListProcessModules(GetCurrentProcessId() );
  return 0;
}

BOOL ListProcessModules( DWORD dwPID ) 
{ 
  HANDLE hModuleSnap = INVALID_HANDLE_VALUE; 
  MODULEENTRY32 me32; 
 
//  Take a snapshot of all modules in the specified process. 
  hModuleSnap = CreateToolhelp32Snapshot( TH32CS_SNAPMODULE, dwPID ); 
  if( hModuleSnap == INVALID_HANDLE_VALUE ) 
  { 
    printError( TEXT("CreateToolhelp32Snapshot (of modules)") ); 
    return( FALSE ); 
  } 
 
//  Set the size of the structure before using it. 
  me32.dwSize = sizeof( MODULEENTRY32 ); 
 
//  Retrieve information about the first module, 
//  and exit if unsuccessful 
  if( !Module32First( hModuleSnap, &me32 ) ) 
  { 
    printError( TEXT("Module32First") );  // Show cause of failure 
    CloseHandle( hModuleSnap );     // Must clean up the snapshot object! 
    return( FALSE ); 
  } 
 
//  Now walk the module list of the process, 
//  and display information about each module 
  do 
  { 
    _tprintf( TEXT("\n\n     MODULE NAME:     %s"),             me32.szModule ); 
    _tprintf( TEXT("\n     executable     = %s"),             me32.szExePath ); 
    _tprintf( TEXT("\n     process ID     = 0x%08X"),         me32.th32ProcessID ); 
    _tprintf( TEXT("\n     ref count (g)  =     0x%04X"),     me32.GlblcntUsage ); 
    _tprintf( TEXT("\n     ref count (p)  =     0x%04X"),     me32.ProccntUsage ); 
    _tprintf( TEXT("\n     base address   = 0x%08X"), (DWORD) me32.modBaseAddr ); 
    _tprintf( TEXT("\n     base size      = %d"),             me32.modBaseSize ); 
 
  } while( Module32Next( hModuleSnap, &me32 ) ); 

    _tprintf( TEXT("\n"));
 
//  Do not forget to clean up the snapshot object. 
  CloseHandle( hModuleSnap ); 
  return( TRUE ); 
} 
 
void printError(TCHAR const* msg )
{
  DWORD eNum;
  TCHAR sysMsg[256];
  TCHAR* p;

  eNum = GetLastError( );
  FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
         NULL, eNum,
         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
         sysMsg, 256, NULL );

  // Trim the end of the line and terminate it with a null
  p = sysMsg;
  while( ( *p > 31 ) || ( *p == 9 ) )
    ++p;
  do { *p-- = 0; } while( ( p >= sysMsg ) &&
                          ( ( *p == '.' ) || ( *p < 33 ) ) );

  // Display the message
  _tprintf( TEXT("\n  WARNING: %s failed with error %d (%s)"), msg, eNum, sysMsg );
}