[hatari-devel] fix null pointer dereference in Dialog

Or more accurately, in SDLGui_CenterDlg, but Dialog_HaltDlg is effectively responsible for the dereference:

Thread 1 "hatari" received signal SIGSEGV, Segmentation fault.

0x0000555555fcf152 in SDLGui_CenterDlg (dlg=dlg@entry=0x5555564d2e80 <haltdlg>) at ../src/gui-sdl/sdlgui.c:224

224 dlg[0].x = (pSdlGuiScrn->w/sdlgui_fontwidth-dlg[0].w)/2;

(gdb) bt

#0 0x0000555555fcf152 in SDLGui_CenterDlg (dlg=dlg@entry=0x5555564d2e80 <haltdlg>) at ../src/gui-sdl/sdlgui.c:224

#1 0x0000555555fccdae in Dialog_HaltDlg () at ../src/gui-sdl/dlgHalt.c:75

#2 0x00005555558ebc9d in cpu_halt (id=2) at ../src/cpu/newcpu.c:6273

#3 Exception_ce000 (nr=2) at ../src/cpu/newcpu.c:3258

#4 ExceptionX (nr=nr@entry=2, address=address@entry=4294967295) at ../src/cpu/newcpu.c:4088

#5 0x00005555558ecf69 in Exception (nr=nr@entry=2) at ../src/cpu/newcpu.c:4125

#6 0x00005555558ed8c9 in bus_error () at ../src/cpu/newcpu.c:4135

#7 0x00005555558ef000 in m68k_run_1_ce () at ../src/cpu/newcpu.c:5808

#8 0x00005555558ee143 in m68k_go (may_quit=may_quit@entry=1) at ../src/cpu/newcpu.c:7640

#9 0x000055555589d814 in M68000_Start () at ../src/m68000.c:298

#10 0x000055555589eb19 in main (argc=1, argv=<optimized out>) at ../src/main.c:946

(gdb) p pSdlGuiScrn

$1 = (SDL_Surface *) 0x0

I ran into this when trying to use the TOS 2.07 Sparrow ROM with a MegaSTE configuration on the current Mercurial tree.

Attached patch ensures we do SDLGui_SetScreen before SDLGui_CenterDlg in Dialog_HaltDlg, which makes the dialog appear as intended.[1]

That said, any news on getting TOS 2.07 running? Just curious...

- Steven

[1] https://i.imgur.com/mF2M8Jl.png

From cb921b68abe1844d31e49ec2024803242e0f852f Mon Sep 17 00:00:00 2001 From: Steven Noonan <steven@xxxxxxxxxxxxxx> Date: Sat, 11 Aug 2018 06:06:41 -0700 Subject: [PATCH] Dialog_HaltDlg: ensure SDLGui screen is set before centering dialog Otherwise we dereference a null pointer in SDLGui_CenterDlg. Signed-off-by: Steven Noonan <steven@xxxxxxxxxxxxxx> --- src/gui-sdl/dlgHalt.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/gui-sdl/dlgHalt.c b/src/gui-sdl/dlgHalt.c index 4aca2d60..0711f28f 100644 --- a/src/gui-sdl/dlgHalt.c +++ b/src/gui-sdl/dlgHalt.c @@ -72,6 +72,9 @@ void Dialog_HaltDlg(void) return; } + if (SDLGui_SetScreen(sdlscrn)) + return; + SDLGui_CenterDlg(haltdlg); switch (SDLGui_DoDialog(haltdlg, NULL, false)) { -- 2.17.0.582.gccdcbd54c4