At an interview I was asked how to by a given vector of integers build resulting vector containing the products of all the elements except current. Below I provided my solution in C++:
#include <vector>
#include <iostream>
using V = std::vector<int>;
V func(const V& v)
{
V result;
result.resize(v.size());
int product = 1;
for (size_t pos = 0; pos != v.size(); ++pos)
{
result[pos] = product;
int a = v[pos];
product *= a;
}
Its Windows client simply crashes with the following message:
My device model number is ZR08WN HDD:2TB and the device QR code ends with 111A:
My Russian registration service provider has stopped working, but PublicDomainRegistry.com sent me the codes and I was able to transfer my domains to some ResellerClub prvider:
It is possible to iterate over std::vector with &&:
#include <vector>
class A {};
int main()
{
std::vector<A> vec;
for (auto&& v : vec)
{
static_cast<void>(v);
}
return 0;
}
I was recently asked during a C++ job interview what are the types of riN variables in the code below:
int val = 25;
int foo() { return val; }
int& foo1() { return val; }
//warning: type qualifiers ignored on function return type
/*const*/ int foo2() { return val; }
const int& foo3() { return val; }
int main()
{
auto ri = foo();
auto ri1 = foo1();
auto ri2 = foo2();
auto ri3 = foo3();
//cannot bind non-const lvalue reference of type 'int&' to an rvalue of type 'int'
//auto& ri4 = foo();
auto& ri5 = foo1();
//cannot bind non-const lvalue reference of type 'int&' to an rvalue of type 'int'
//auto& ri6 = foo2();
auto& ri7 = foo3();
auto&& ri8 = foo();
auto&& ri9 = foo1();
auto&& ri10 = foo2();
auto&& ri11 = foo3();
return 0;
}
auto ignores the type qualifiers and references, so looks like the types are simply int, int& and int&&.
The call stack is:
#00 pc 00000000000097a8 /system/lib/libutils.so (android::RefBase::incStrong(void const*) const+4)
#00 pc 0000000000022145 /vendor/lib/libIMGegl.so
#00 pc 000000000000ab79 /vendor/lib/libIMGegl.so (KEGLGetDrawableParameters+252)
#00 pc 0000000000041c53 /vendor/lib/egl/libGLESv2_mtk.so
#00 pc 000000000001663d /vendor/lib/egl/libGLESv2_mtk.so
#00 pc 0000000000016b01 /vendor/lib/egl/libGLESv2_mtk.so (glClear+440)
#00 pc 000000000008acaf /data/app/net.geographx.LinesGame-9_pUex92-tGEqE4iIbRCCw==/lib/arm/libLinesGameQt_armeabi-v7a.so (LinesGame::Squircle::beforeRendering()+270)
#00 pc 000000000017d5b9 /data/app/net.geographx.LinesGame-9_pUex92-tGEqE4iIbRCCw==/lib/arm/libQt5Core_armeabi-v7a.so
#00 pc 0000000000176f4d /data/app/net.geographx.LinesGame-9_pUex92-tGEqE4iIbRCCw==/lib/arm/libQt5Quick_armeabi-v7a.so (QQuickWindowPrivate::renderSceneGraph(QSize const&, QSize const&)+172)
It is a QT bug that is not fixed yet.
Also my app crashes at the destructor of std::thread and this also a QT bug that is not fixed yet.
Below I proved the results of speed tests of my 500 GB SSD M.2 Kingston NV1 [SNVS/500G] and 500 GB SSD M.2 Seagate BarraCuda Q5 [ZP500CV3A001]:
------------------------------------------------------------------------------
CrystalDiskMark 8.0.1 x64 (UWP) (C) 2007-2021 hiyohiyo
Crystal Dew World: https://crystalmark.info/
------------------------------------------------------------------------------
* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes
[Read]
SEQ 1MiB (Q= 8, T= 1): 2546.163 MB/s [ 2428.2 IOPS] < 3291.40 us>
SEQ 1MiB (Q= 1, T= 1): 0.000 MB/s [ 0.0 IOPS] < 0.00 us>
RND 4KiB (Q= 32, T= 1): 449.897 MB/s [ 109838.1 IOPS] < 281.99 us>
RND 4KiB (Q= 1, T= 1): 0.000 MB/s [ 0.0 IOPS] < 0.00 us>
[Write]
SEQ 1MiB (Q= 8, T= 1): 1970.445 MB/s [ 1879.2 IOPS] < 4243.49 us>
SEQ 1MiB (Q= 1, T= 1): 0.000 MB/s [ 0.0 IOPS] < 0.00 us>
RND 4KiB (Q= 32, T= 1): 310.284 MB/s [ 75752.9 IOPS] < 417.44 us>
RND 4KiB (Q= 1, T= 1): 0.000 MB/s [ 0.0 IOPS] < 0.00 us>
Profile: Default
Test: 1 GiB (x5) [D: 18% (85/466GiB)]
Mode:
Time: Measure 5 sec / Interval 5 sec
Date: 2021/05/16 13:23:57
OS: Windows 10 Professional [10.0 Build 19041] (x64)
There was a bug in QT 5.15.2 that results in app crash on Android 5.1 and a patch:
Submodule qtbase contains modified content
diff --git a/qtbase/src/corelib/plugin/qlibrary_unix.cpp b/qtbase/src/corelib/plugin/qlibrary_unix.cpp
index a5c72f81d9..5cd21b67a4 100644
--- a/qtbase/src/corelib/plugin/qlibrary_unix.cpp
+++ b/qtbase/src/corelib/plugin/qlibrary_unix.cpp
@@ -243,10 +243,10 @@ bool QLibraryPrivate::load_sys()
}
if (hnd) {
using JniOnLoadPtr = jint (*)(JavaVM *vm, void *reserved);
- JniOnLoadPtr jniOnLoad = reinterpret_cast<JniOnLoadPtr>(dlsym(pHnd, "JNI_OnLoad"));
+ JniOnLoadPtr jniOnLoad = reinterpret_cast<JniOnLoadPtr>(dlsym(hnd, "JNI_OnLoad"));
if (jniOnLoad && jniOnLoad(QtAndroidPrivate::javaVM(), nullptr) == JNI_ERR) {
dlclose(hnd);
- pHnd = nullptr;
+ hnd = nullptr;
}
}
#endif
Looks like it was simply a typo and pHnd was replaced with hnd.
QT 5.15.3 where the bug was fixed is commercial so I applied the patch by myself (thanks to danilabagroff from stackoverflow.com):
Theoretically it can be:
git clone --recursive https://code.qt.io/qt/qt5.git --branch v6.1.0
or alternatively:
git clone https://code.qt.io/qt/qt5.git --branch v6.1.0
./init-repository --branch --module-subset=essential,qtandroidextras,qtsvg,qtquickcontrols2,qtgraphicaleffects,qtwebsockets,qtmultimedia
or
./init-repository --module-subset=all
My QT 5.15.2 app crashes on Android 5.1 with the following call stack:
*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
Build fingerprint: 'Android/sdk_google_phone_x86_64/generic_x86_64:5.1.1/LMY48X/6402608:userdebug/test-keys'
Revision: '0'
ABI: 'x86_64'
pid: 3954, tid: 3998, name: qtMainLoopThrea >>> net.geographx.LinesGame <<<
signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
Abort message: 'art/runtime/mirror/art_method.cc:356] Check failed: !IsFastNative() int java.lang.Character.digitImpl!(int, int)'
rax 0000000000000000 rbx 0000000000000f9e rcx ffffffffffffffff rdx 0000000000000006
rsi 0000000000000f9e rdi 0000000000000f72
r8 0000000000000022 r9 0000000000000002 r10 0000000000000008 r11 0000000000000206
r12 000000000000000b r13 0000000000000006 r14 00007f747b51a000 r15 0000000000000051
cs 0000000000000033 ss 000000000000002b
rip 00007f7488099e37 rbp 00007f7467007b70 rsp 00007f74670063e8 eflags 0000000000000206
