[Mesa-dev] [PATCH] Fixes assertion fail on startup in `glXCreateContextAttribsARB`.

[zegentzy at protonmail.com]

>From 05468bf625317e76adb43aa8ef20375cc179dd12 Mon Sep 17 00:00:00 2001
From: Hal Gentz <zegentzy at protonmail.com>
Date: Sun, 24 Mar 2019 16:52:39 -0600
Subject: [PATCH] Fixes assertion fail on startup in
 `glXCreateContextAttribsARB`.

To quote Uli Schlachter, who understands this stuff more than I do:

>   The function __glXSendError() in mesa's src/glx/glx_error.c invents an X11
> protocol error out of thin air. For the sequence number it uses dpy->request.
> This is the sequence number of the last request that was sent. _XError() will
> then update dpy->last_request_read based on the sequence number of the error
> that just "came in".
>
>   If now another something comes in with a sequence number less than
> dpy->last_request_read, since sequence numbers are monotonically increasing,
> widen() will incorrectly add 1<<32 to the sequence number and things might go
> downhill afterwards.

`__glXSendErrorForXcb` was also patched, as that's the function that
`glXCreateContextAttribsARB` actually uses.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99781

Signed-off-by: Hal Gentz <zegentzy at protonmail.com>
---
 src/glx/glx_error.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/glx/glx_error.c b/src/glx/glx_error.c
index 653cbeb2d2a..712ecf8213d 100644
--- a/src/glx/glx_error.c
+++ b/src/glx/glx_error.c
@@ -54,7 +54,7 @@ __glXSendError(Display * dpy, int_fast8_t errorCode, uint_fast32_t resourceID,
       error.errorCode = glx_dpy->codes->first_error + errorCode;
    }

-   error.sequenceNumber = dpy->request;
+   error.sequenceNumber = dpy->last_request_read;
    error.resourceID = resourceID;
    error.minorCode = minorCode;
    error.majorCode = glx_dpy->majorOpcode;
@@ -73,7 +73,7 @@ __glXSendErrorForXcb(Display * dpy, const xcb_generic_error_t *err)

    error.type = X_Error;
    error.errorCode = err->error_code;
-   error.sequenceNumber = err->sequence;
+   error.sequenceNumber = dpy->last_request_read;
    error.resourceID = err->resource_id;
    error.minorCode = err->minor_code;
    error.majorCode = err->major_code;
--
2.21.0