Bug 100293

I found a big problem with RandR1.2 gamma code v6, which is now
commited in main xserver.

I mean this commit:
commit b4e46c0444bb09f4af59d9d13acc939a0fbbc6d6
Author: Michel Dänzer <michel.daenzer@amd.com>
Date:   Sat Nov 28 16:50:47 2015 +0900

The problem is, that it is crashing the Xserver when I have
xinerama enabled. I am using two nvidia cards with two
outputs enabled for each. So my working configuration is really
great for tests, because I am using 4 monitors at a time :)

The backtrace for the crash is:
[498150.564] (EE) Backtrace:
[498150.564] (EE) 0: ./Xorg (xorg_backtrace+0x3d) [0x55d361ec194d]
[498150.564] (EE) 1: ./Xorg (0x55d361d1e000+0x1a72a9) [0x55d361ec52a9]
[498150.564] (EE) 2: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7f683870c000+0x110c0) [0x7f683871d0c0]
[498150.564] (EE) 3: ./Xorg (RRCrtcGammaSetSize+0x0) [0x55d361e26a10]
[498150.564] (EE) 4: ./Xorg (0x55d361d1e000+0xcda5a) [0x55d361deba5a]
[498150.564] (EE) 5: ./Xorg (xf86HandleColormaps+0x302) [0x55d361db6b12]
[498150.564] (EE) 6: /dev/shm/a/gfx-test/lib/xorg/modules/drivers/nouveau_drv.so (0x7f6832dcb000+0x10887) [0x7f6832ddb887]
[498150.564] (EE) 7: ./Xorg (AddScreen+0xd7) [0x55d361d6def7]
[498150.564] (EE) 8: ./Xorg (InitOutput+0x410) [0x55d361db1950]
[498150.564] (EE) 9: ./Xorg (0x55d361d1e000+0x53946) [0x55d361d71946]
[498150.565] (EE) 10: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xf1) [0x7f683838e2b1]
[498150.565] (EE) 11: ./Xorg (_start+0x2a) [0x55d361d5cafa]
[498150.565] (EE)
[498150.565] (EE) Segmentation fault at address 0x38
[498150.565] (EE)
Fatal server error:
[498150.565] (EE) Caught signal 11 (Segmentation fault). Server aborting

I was doing the final tests on the following tagged version:
7e5c9bdf7 (tag: xorg-server-1.19.0) Bump version to 1.19.0

I prepared a patch which is a solution for the problem:
diff --git a/hw/xfree86/common/xf86cmap.c b/hw/xfree86/common/xf86cmap.c
index 8588c9fba..c43aceec9 100644
--- a/hw/xfree86/common/xf86cmap.c
+++ b/hw/xfree86/common/xf86cmap.c
@@ -155,6 +155,9 @@ xf86HandleColormaps(ScreenPtr pScreen,
     int *indices;
     int elements;

+    if (xf86_crtc_supports_gamma(pScrn))
+      return TRUE;
+
     if (!maxColors || !sigRGBbits ||
         (!loadPalette && !xf86_crtc_supports_gamma(pScrn)))
         return FALSE;

After applying the patch, the server is not crashing anymore.