Running Krita development version in callgrind causes a crash at startup. The backtrace points to some point in the new c++11 stdlib random number facility. There is some mention of Vc SIMD library in the backtrace, but the call to std::random_device happens before any SIMD operations are invoked so I doubt that is the issue. 

The call occurs around line 165 here: https://phabricator.kde.org/diffusion/KRITA/browse/master/krita/image/kis_brush_mask_applicators.h


vex amd64->IR: unhandled instruction bytes: 0xF 0xC7 0xF0 0x89 0x6 0xF 0x42 0xC1
vex amd64->IR:   REX=0 REX.W=0 REX.R=0 REX.X=0 REX.B=0
vex amd64->IR:   VEX=0 VEX.L=0 VEX.nVVVV=0x0 ESC=0F
vex amd64->IR:   PFX.66=0 PFX.F2=0 PFX.F3=0
==18052== valgrind: Unrecognised instruction at address 0x6a75ec5.
==18052==    at 0x6A75EC5: std::(anonymous namespace)::__x86_rdrand() (random.cc:69)
==18052==    by 0x6A76061: std::random_device::_M_getval() (random.cc:130)
==18052==    by 0x869FF59: std::random_device::operator()() (in ~/lib/x86_64-linux-gnu/libkritaimage.so.15.0.0)
==18052==    by 0x86A04C4: KisBrushMaskScalarApplicator<KisCircleMaskGenerator, (Vc::Implementation)6>::processScalar(QRect const&) (in ~/lib/x86_64-linux-gnu/libkritaimage.so.15.0.0)