Opened 17 years ago

Closed 17 years ago

#2103 closed task (fixed)

The view is shifted 50% to the left in many OpenGL apps on ati video cards

Reported by: alexander@… Owned by: dnicholson@…
Priority: normal Milestone: 6.2.0
Component: BOOK Version: SVN
Severity: major Keywords:


This is a duplicate of

The patch attached there fixes the problem only for r300 cards, and is thus incomplete. A workaround that works for all cards is to change the "make linux-dri" command in Mesa instructions to:

make OPT_FLAGS="-O2 -pipe -fno-strict-aliasing" linux-dri-x86

The important part is -fno-strict-aliasing.

Change History (5)

comment:1 by dnicholson@…, 17 years ago

Owner: changed from blfs-book@… to dnicholson@…
Status: newassigned

I haven't given this much thought as I have an r200 card and these things work fine for me.

Alexander, do you think it's fine to add -fno-strict-aliasing for everything? Surely it can't hurt. This seems like an easy workaround.

comment:2 by alexander@…, 17 years ago

That's even the workaround recommended by Mesa developers: "That said, there are still potential aliasing problems in the code, I'd suggest you compile with -fno-strict-aliasing for the time being."

comment:3 by alexander@…, 17 years ago

If you were asking about "-fno-strict-aliasing for everything, not just Mesa", +1. The LiveCD already does this, because there were too many issues without this flag. Slirp (both standalone and as a part of qemu), MySQL, and Mesa come to mind, and the breakage is at runtime in all such cases.

comment:4 by dnicholson@…, 17 years ago

Going to add -fno-strict-aliasing. I do agree with the use of linux-dri-x86 since the book only supports x86 and it adds a few nice things on top of the linux-dri target. Plus, anyone using a different arch following the book should be able to figure out how to substitute the correct config file. Here's the linux-dri-x86 config file:

# -*-makefile-*-
# Configuration for linux-dri: Linux DRI hardware drivers for XFree86 & others

include $(TOP)/configs/linux-dri

CONFIG_NAME = linux-dri-x86

# Unnecessary on x86, generally.

# Add -m32 to CFLAGS:

ASM_API = $(X86_API)

However, although '-O2 -pipe' are very safe CFLAGS, we don't set the optimization flags anywhere else in the book (that I know of). Instead, I'm plan to add this sed:

sed -i 's/^OPT_FLAGS  =.*/& -fno-strict-aliasing/' configs/linux-dri

Anyone who knows what they're doing can always override OPT_FLAGS at build time.

Comments on the change from the linux-dri target to the linux-dri-x86 target and the above sed?

comment:5 by dnicholson@…, 17 years ago

Resolution: fixed
Status: assignedclosed

Changed my mind on both things. I'm passing OPT_FLAGS="-O2 -fno-strict-aliasing" to the make command. This is the correct way to do things with make. And there are a couple other places in the book where we do things like this.

And I changed the target to linux-dri-x86. It adds a few nice flags that would probably added if a typical configure script is used. I mentioned the location to look for other targets if the arch isn't x86.

Fixed in r6324.

Note: See TracTickets for help on using tickets.