GitLab

GHC 6.10.1 seems to generate incorrect code for createWindow in X11-1.4.3 on x86_64 when optimizations are on.

    $ ghc-6.10.1 -fforce-recomp --make simple.hs -O0 -o simple
    $ ghc-6.10.1 -fforce-recomp --make simple.hs -O -o simple_optimized

When built with no optimizations, the program succeeds:

    $ ./simple
    (33554433,Display 0x0000000001192dd0,Screen 0x0000000001193a40,194)

When built with optimizations, the X server sends an error about an invalid parameter to a XCreateWindow call:

    $ ./simple_optimized 
    (33554433,Display 0x0000000000b91dd0,Screen 0x0000000000b92a40,194)
    X Error of failed request:  BadMatch (invalid parameter attributes)
      Major opcode of failed request:  1 (X_CreateWindow)
      Serial number of failed request:  7
      Current serial number in output stream:  8

We set a breakpoint at XCreateWindow to check the arguments passed, note that depth takes the correct value in the non-optimized version:

    $ gdb simple
    (gdb) break XCreateWindow
    (gdb) run
    ...
    Breakpoint 1, XCreateWindow (dpy=0x172bde0, parent=194, x=0, y=0, width=100, height=100, 
        borderWidth=0, depth=24, class=1, visual=0x17333d0, valuemask=512, 
        attributes=0x7f920a77e040) at ../../src/Window.c:115
    115     ../../src/Window.c: No such file or directory.
        in ../../src/Window.c

The optimized version has "depth=38044640", which is total nonsense. The value seems to change from run to run.

    $ gdb simple_optimized
    (gdb) break XCreateWindow
    (gdb) run
    ...
    Breakpoint 1, XCreateWindow (dpy=0x2440df0, parent=194, x=0, y=0, width=100, height=100, 
        borderWidth=0, depth=38044640, class=1, visual=0x24483e0, valuemask=512, 
        attributes=0x7f84f577e040) at ../../src/Window.c:115
    115     ../../src/Window.c: No such file or directory.
        in ../../src/Window.c

We discovered this bug in xmonad (http://xmonad.org/bugs/226), and have temporarily worked around it by using Cabal's --disable-optimization flag.

Trac metadata

Trac field	Value
Version	6.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (FFI)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture