winedos: Print better diagnostics when a DOS app fails to start.

dlls/kernel32/wowthunk.c

@@ -593,7 +593,7 @@ BOOL WINAPI K32WOWCallback16Ex( DWORD vpfn16, DWORD dwFlags,
             __wine_pop_frame( &frame );
             if (errno != 0)  /* enter_vm86 will fall with ENOSYS on x64 kernels */
             {
-                ERR("__wine_enter_vm86 failed (errno=%d)\n", errno);
+                WARN("__wine_enter_vm86 failed (errno=%d)\n", errno);
                 if (errno == ENOSYS)
                     SetLastError(ERROR_NOT_SUPPORTED);
                 else

dlls/winedos/dosmem.c

@@ -511,8 +511,6 @@ BOOL DOSMEM_MapDosLayout(void)
             ERR( "Need full access to the first megabyte for DOS mode\n" );
             ExitProcess(1);
         }
-        MESSAGE( "Warning: unprotecting memory to allow real-mode calls.\n"
-                 "         NULL pointer accesses will no longer be caught.\n" );
         /* copy the BIOS and ISR area down */
         memcpy( DOSMEM_dosmem, DOSMEM_sysmem, 0x400 + 0x100 );
         DOSMEM_sysmem = DOSMEM_dosmem;

dlls/winedos/dosvm.c

@@ -569,15 +569,16 @@ static LONG WINAPI exception_handler(EXCEPTION_POINTERS *eptr)
   return EXCEPTION_CONTINUE_SEARCH;
 }
 
-int WINAPI DOSVM_Enter( CONTEXT86 *context )
+INT WINAPI DOSVM_Enter( CONTEXT86 *context )
 {
+  INT ret = 0;
   if (!ISV86(context))
       ERR( "Called with protected mode context!\n" );
 
   __TRY
   {
-      WOWCallback16Ex( 0, WCB16_REGS, 0, NULL, (DWORD *)context );
-      TRACE_(module)( "vm86 returned: %s\n", strerror(errno) );
+      if (!WOWCallback16Ex( 0, WCB16_REGS, 0, NULL, (DWORD *)context )) ret = -1;
+      TRACE_(module)( "ret %d err %u\n", ret, GetLastError() );
   }
   __EXCEPT(exception_handler)
   {
@@ -585,7 +586,7 @@ int WINAPI DOSVM_Enter( CONTEXT86 *context )
   }
   __ENDTRY
 
-  return 0;
+  return ret;
 }
 
 /***********************************************************************
@@ -645,8 +646,8 @@ void WINAPI DOSVM_PIC_ioport_out( WORD port, BYTE val)
  */
 INT WINAPI DOSVM_Enter( CONTEXT86 *context )
 {
- ERR_(module)("DOS realmode not supported on this architecture!\n");
- return -1;
+    SetLastError( ERROR_NOT_SUPPORTED );
+    return -1;
 }
 
 /***********************************************************************

dlls/winedos/module.c

@@ -614,7 +614,7 @@ void WINAPI MZ_RunInThread( PAPCFUNC proc, ULONG_PTR arg )
 static DWORD WINAPI MZ_DOSVM( LPVOID lpExtra )
 {
   CONTEXT context;
-  DWORD ret;
+  INT ret;
 
   dosvm_pid = getpid();
 
@@ -628,9 +628,23 @@ static DWORD WINAPI MZ_DOSVM( LPVOID lpExtra )
   context.EFlags = V86_FLAG | VIF_MASK;
   DOSVM_SetTimer(0x10000);
   ret = DOSVM_Enter( &context );
-
+  if (ret == -1)
+  {
+      /* fetch the app name from the environment */
+      PDB16 *psp = PTR_REAL_TO_LIN( DOSVM_psp, 0 );
+      char *env = PTR_REAL_TO_LIN( psp->environment, 0 );
+      while (*env) env += strlen(env) + 1;
+      env += 1 + sizeof(WORD);
+
+      if (GetLastError() == ERROR_NOT_SUPPORTED)
+          MESSAGE( "wine: Cannot start DOS application %s\n"
+                   "      because vm86 mode is not supported on this platform.\n",
+                   debugstr_a(env) );
+      else
+          FIXME( "vm86 mode failed error %u\n", GetLastError() );
+  }
   dosvm_pid = 0;
-  return ret;
+  return ret != 0;
 }
 
 static BOOL MZ_InitTask(void)