Re: Strange problem with EPICS areaDetector

[Timo Korhonen via Tech-talk <tech-talk at aps.anl.gov>]

FWIW, this is what Ubuntu Wiki says on this matter:

https://urldefense.us/v3/__https://wiki.ubuntu.com/ToolChain/CompilerFlags*A-D_FORTIFY_SOURCE.3D3__;Iw!!G_uCfscf7eWS!ZXiAoKEIMfSS5NRgNhpT13otpnk7lIGejq1oXlNUwp2mQ5JomY6QGUoe7AxKez9xOToVpx40cY7O4IycM8t9IpWIFj5k$ 

"... Only activated when compiled with -O1 or higher."

A little bit odd is that the page also says "First enabled as -D_FORTIFY_SOURCE=2 in Ubuntu 8.10 and updated to -D_FORITFY_SOURCE=3 in Ubuntu 24.04." Apparently the update was already applied in Ubuntu 22.04.

Timo


On 2024-06-20, 08:52, "Tech-talk on behalf of Jörn Dreyer via Tech-talk" <tech-talk-bounces at aps.anl.gov <mailto:tech-talk-bounces at aps.anl.gov> on behalf of tech-talk at aps.anl.gov <mailto:tech-talk at aps.anl.gov>> wrote:


Hi Michael,


yes, you are right that the level of optimization plays a role wether the check triggers a fault or not.
At leas thats what the documentation of the _FORTIFY_SOURCE macro says.


Jörn


Am Donnerstag, 20. Juni 2024, 07:28:29 MESZ schrieb Michael Davidsaver via Tech-talk:
> On 6/19/24 21:26, Michael Davidsaver wrote:
> > I see something like the following. All of the 'f's mean that GCC
> > is unable to track the sizes of the objects involved. I also don't
> > see a fault.
> > 
> >> X test.LINR ptemp=ffffffffffffffff,ffffffffffffffff papChoice=ffffffffffffffff,ffffffffffffffff i=0 
> 
> I spoke too soon. I can reproduce, but not with a -debug build.
> So I guess '-O2' vs '-O3' plays some role?
> 
> > X test.LINR ptemp=ffffffffffffffff,28 papChoice=ffffffffffffffff,ffffffffffffffff i=0
> > X test.LINR ptemp=ffffffffffffffff,0 papChoice=ffffffffffffffff,ffffffffffffffff i=1
> > *** buffer overflow detected ***: terminated
> 
> The inferred size of 'ptemp' is 28 bytes, which I can only assume comes from
> this line.
> 
> > ptemp = &(pdbr_enumStrs->strs[0][0]);
> 
> I don't understand why 28 and not 1, 30, or 30*40 ?
> 
> The first iteration steps past this.
> 
> > ptemp += sizeof(pdbr_enumStrs->strs[0]);
> 
> This is certainly an odd way to iterate an array...
> 
>