[Lazarus] Windows startup infinite loop

[Henry Vermaak]

On Wed, Feb 13, 2019 at 05:37:10PM +0000, Henry Vermaak wrote:
> We're having a strange problem here, an infinite loop happens on a customer's
> machine just after the main form is created.  It doesn't happen when the
> program is run inside a debugger and it only happens on the customer's
> machine(s), so it's probably related to their Windows configuration.
> 
> The infinite loop is not in our code (probably happens with HandleNeeded() is
> called for the main form).  When I attach gdb manually when the program is run
> outside the debugger I can get a stack trace that shows the loop:
> 
> (gdb) thread 1
> [Switching to thread 1 (Thread 4484.0x2bc8)]
> #0  0x76d2566b in USER32!DispatchMessageW () from C:\WINDOWS\System32\user32.dll
> (gdb) bt
> #0  0x76d2566b in USER32!DispatchMessageW () from C:\WINDOWS\System32\user32.dll
> #1  0x76d1b387 in USER32!CallWindowProcW () from C:\WINDOWS\System32\user32.dll
> #2  0x005076ab in CALLDEFAULTWINDOWPROC (WINDOW=592304, MSG=48, WPARAM=-854972773, LPARAM=0)
>     at ./win32/win32callback.inc:97
> #3  0x0050bb80 in TWINDOWPROCHELPER__DOWINDOWPROC (this=0xf3e7e1c) at ./win32/win32callback.inc:2419
> #4  0x0050c4fb in WINDOWPROC (WINDOW=592304, MSG=48, WPARAM=-854972773, LPARAM=0) at ./win32/win32callback.inc:2673
> #5  0x76d334bb in USER32!AddClipboardFormatListener () from C:\WINDOWS\System32\user32.dll
> #6  0x76d25913 in USER32!DispatchMessageW () from C:\WINDOWS\System32\user32.dll
> #7  0x76d1b387 in USER32!CallWindowProcW () from C:\WINDOWS\System32\user32.dll
> #8  0x72e6fd6d in ?? ()
> #9  0x72e6f8ef in ?? ()
> #10 0x76d334bb in USER32!AddClipboardFormatListener () from C:\WINDOWS\System32\user32.dll
> #11 0x76d25913 in USER32!DispatchMessageW () from C:\WINDOWS\System32\user32.dll
> #12 0x76d1b387 in USER32!CallWindowProcW () from C:\WINDOWS\System32\user32.dll
> #13 0x005076ab in CALLDEFAULTWINDOWPROC (WINDOW=592304, MSG=48, WPARAM=-854972773, LPARAM=0)
>     at ./win32/win32callback.inc:97
> #14 0x0050bb80 in TWINDOWPROCHELPER__DOWINDOWPROC (this=0xf3e7cf4) at ./win32/win32callback.inc:2419
> #15 0x0050c4fb in WINDOWPROC (WINDOW=592304, MSG=48, WPARAM=-854972773, LPARAM=0) at ./win32/win32callback.inc:2673
> #16 0x76d334bb in USER32!AddClipboardFormatListener () from C:\WINDOWS\System32\user32.dll
> #17 0x76d25913 in USER32!DispatchMessageW () from C:\WINDOWS\System32\user32.dll
> #18 0x76d1b387 in USER32!CallWindowProcW () from C:\WINDOWS\System32\user32.dll
> #19 0x72e6fd6d in ?? ()
> #20 0x72e6f8ef in ?? ()
> #21 0x76d334bb in USER32!AddClipboardFormatListener () from C:\WINDOWS\System32\user32.dll
> #22 0x76d25913 in USER32!DispatchMessageW () from C:\WINDOWS\System32\user32.dll
> #23 0x76d1b387 in USER32!CallWindowProcW () from C:\WINDOWS\System32\user32.dll
> #24 0x005076ab in CALLDEFAULTWINDOWPROC (WINDOW=592304, MSG=48, WPARAM=-854972773, LPARAM=0)
>     at ./win32/win32callback.inc:97
> #25 0x0050bb80 in TWINDOWPROCHELPER__DOWINDOWPROC (this=0xf3e7bcc) at ./win32/win32callback.inc:2419
> 
> It carries on like this until you stop with ctrl-c.  I was wondering if this
> rang a bell for anyone?  I'm running on the fixes_2_0 branch now, but the
> problem existed with fixes_1_8 too.
> 
> Is there anything I can do to help get to the bottom of this?  Will rebuilding
> the LCL with MSG_DEBUG help?

Rebuilding the LCL with MSG_DEBUG shows that it has something to do with
WM_SETFONT:

Done: Main form
WindowProc called for window=00020C12 msg=WM_GETMINMAXINFO wparam=00000000 lparam=040AF69C
WindowProc called for window=00020C12 msg=WM_NCCREATE wparam=00000000 lparam=040AF690
WindowProc called for window=00020C12 msg=WM_NCCALCSIZE wparam=00000000 lparam=040AF67C
WindowProc called for window=00020C12 msg=WM_CREATE wparam=00000000 lparam=040AF690
WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
#WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
##WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
###WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
####WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
#####WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
######WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
#######WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000
########WindowProc called for window=00020C12 msg=WM_SETFONT wparam=E60A1591 lparam=00000000

That just continues until you kill the program.  Any ideas?

Henry