On 30/07/2018 16:33, tumtum00 wrote:
after building xorg-server 1.20.0 without errors, the XWin binary crashes at
startup due to a buffer overflow. XWin 1.20.0 from Cygwin repos works as
expected.
Setup:
- Freshly installed Win7 x86_64 VM
- Cygwin x86_64
- Dependencies installed as described in
https://x.cygwin.com/docs/cg/prog-build-prerequisites.html, plus
xcb-composite-devel
Thanks for pointing out this oversight. I will amend the documentation.
- Applied the following patches to my Cygwin environment, otherwise the build
would fail:
https://github.com/cygwinports/cygport/commit/1072fd872757bd7aa97fa8daf95ed13f70f56291
https://github.com/cygwinports/cygport/commit/c4e0f0ec5f9a5a691fd19efe2bda3cdf278baef5
- Downloaded patched xorg-server 1.20.0-2 sources as described in
https://x.cygwin.com/docs/cg/prog-obtaining-source.html, "Obtaining via Cygwin
setup"
Build:
$ cygport --64 xorg-server.cygport prep
$ cygport --64 xorg-server.cygport compile
XWin binary
/usr/src/xorg-server-1.20.0-2.src/xorg-server-1.20.0-2.x86_64/src/xserver-cygwin-1.20.0-2/x86_64-pc-cygwin/hw/xwin/XWin
is then executed.
The `--buildtype=debug` option was added to `cygmeson` in `xorg-server.cygport`
to generate the attached reports.
I'm out of ideas on how to continue debugging this. Help would be much
appreciated.
I tried to reproduce this problem by following these steps, but the
produced executable works ok for me.
#7 0x000000018017e7e9 in __chk_fail () at
/usr/src/debug/cygwin-2.10.0-1/newlib/libc/ssp/chk_fail.c:11
msg = "*** buffer overflow detected ***: terminated\n"
#8 0x000000018018c1c3 in __memcpy_chk (dst=0x60008e570, src=0x45, len=0,
slen=0) at /usr/src/debug/cygwin-2.10.0-1/newlib/libc/ssp/memcpy_chk.c:48
This is a wrapper around memcpy, which is being used as we are building
with _FORTIFY_SOURCE
I'd suggest setting a breakpoint on this line (after installing the
cygwin-debuginfo package for relevant debug info) and trying to
understand why it's not succeeding.
No locals.
#9 0x00000001004b80d5 in RRConfigureOutputProperty (output=output@entry=0x60008e570,
property=<optimized out>, pending=pending@entry=0, range=range@entry=0,
immutable=immutable@entry=0, num_values=num_values@entry=2,
values=values@entry=0x10059f4b0 <values>) at ../randr/rrproperty.c:385
prop = 0x60008cff0
add = <optimized out>
new_values = 0x60008e650
#10 0x00000001004b682e in RROutputCreate (pScreen=pScreen@entry=0x60008bff0,
name=name@entry=0x100586942 <__func__.9648+722> "default",
nameLength=nameLength@entry=7,
devPrivate=devPrivate@entry=0x0) at ../randr/rroutput.c:120
values = {0, 1}
output = 0x60008e570
outputs = <optimized out>
nonDesktopAtom = <optimized out>
#11 0x000000010040c11b in winRandRInit (pScreen=pScreen@entry=0x60008bff0) at
../hw/xwin/winrandr.c:256
crtc = 0x60008e240
output = <optimized out>
--
Jon Turney
Volunteer Cygwin/X X Server maintainer
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