void QTimer::start(std::chrono::milliseconds interval) Starts or restarts the timer with a timeout of duration interval milliseconds.
This is equivalent to:
timer.setInterval(interval); timer.start();
If the timer is already running, it will be stopped and restarted. This will also change its id().
If singleShot is true, the timer will be activated only once.
Starting from Qt 6.10, setting a negative interval will result in a run-time warning and the value being reset to 1ms. Before Qt 6.10 a Qt Timer would let you set a negative interval but behave in surprising ways (for example stop the timer if it was running or not start it at all).
It is very convenient to use this function because you do not need to bother with a timerEvent or create a local QTimer object.
If context is specified, then the functor will be called only if the context object has not been destroyed before the interval occurs. The functor will then be run the thread of context. The context's thread must have a running Qt event loop.
If functor is a member function of context, then the function will be called on the object.
The interval parameter can be an int (interpreted as a millisecond count) or a std::chrono type that implicitly converts to nanoseconds.
Starting from Qt 6.10, setting a negative interval will result in a run-time warning and the value being reset to 1ms. Before Qt 6.10 a Qt Timer would let you set a negative interval but behave in surprising ways (for example stop the timer if it was running or not start it at all).
// Note. The Q_OBJECT macro starts a private section. // To declare public members, use the 'public:' access modifier. public: Counter() { m_value = 0; }
This property holds the index position of the widget that is visible The current index is -1 if there is no current widget. By default, this property contains a value of -1 because the stack is initially empty.
sx1276 예제를 보다보니 mbed쪽(?) 드라이버 소스에 함수인데 "= 0"를 해둔게 있어서 이게 머야 하고 검색해보니
순수 가상 함수라는 이상한(?) 이름이 붙은 녀석이 발견되었다.
어떻게 보면 java에서 interface 로 선언되는 녀석과 비슷하게 실 구현체가 없이 선언되고
무조건 구현해서 사용해야 하는 녀석 같은데.. 참 난해한 문법형태구만..
그런데 cpp에 원래 virtual 키워드가 있었던..가?
/*! * @brief Checks if the given RF frequency is supported by the hardware * * @param [IN] frequency RF frequency to be checked * @retval isSupported [true: supported, false: unsupported] */ virtual bool CheckRfFrequency( uint32_t frequency ) = 0;
class Base { public: virtual void NameOf(); // Virtual function. void InvokingClass(); // Nonvirtual function. };
// Implement the two functions. void Base::NameOf() { cout << "Base::NameOf\n"; }
void Base::InvokingClass() { cout << "Invoked by Base\n"; }
class Derived : public Base { public: void NameOf(); // Virtual function. void InvokingClass(); // Nonvirtual function. };
// Implement the two functions. void Derived::NameOf() { cout << "Derived::NameOf\n"; }
void Derived::InvokingClass() { cout << "Invoked by Derived\n"; }
int main() { // Declare an object of type Derived. Derived aDerived;
// Declare two pointers, one of type Derived * and the other // of type Base *, and initialize them to point to aDerived. Derived *pDerived = &aDerived; Base *pBase = &aDerived;
특이한게 배열 loop 돌다 터지는게 아니라 다 돌고 나서 free 가려다가 터진다. 신기하네
$ gcc t2.c -g -fsanitize=address $ ./a.out ================================================================= ==2713847==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x504000000038 at pc 0x609d568b42e0 bp 0x7ffdaa34e820 sp 0x7ffdaa34e810 WRITE of size 4 at 0x504000000038 thread T0 #0 0x609d568b42df in main /home/minimonk/work/src/malloc/t2.c:9 #1 0x7cc2e8429d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58 #2 0x7cc2e8429e3f in __libc_start_main_impl ../csu/libc-start.c:392 #3 0x609d568b41a4 in _start (/home/minimonk/work/src/malloc/a.out+0x11a4)
0x504000000038 is located 0 bytes to the right of 40-byte region [0x504000000010,0x504000000038) allocated by thread T0 here: #0 0x7cc2e88b4887 in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145 #1 0x609d568b4286 in main /home/minimonk/work/src/malloc/t2.c:7 #2 0x7cc2e8429d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
SUMMARY: AddressSanitizer: heap-buffer-overflow /home/minimonk/work/src/malloc/t2.c:9 in main Shadow bytes around the buggy address: 0x0a087fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0a087fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0a087fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0a087fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0a087fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0x0a087fff8000: fa fa 00 00 00 00 00[fa]fa fa fa fa fa fa fa fa 0x0a087fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0a087fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0a087fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0a087fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0a087fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb Shadow gap: cc ==2713847==ABORTING
idx 값을 보면 10000번 돌았는데
printf 하려고 하면 바로 malloc(): corrupted top size 하면서 터진다.
$ gdb ./a.out GNU gdb (Ubuntu 12.1-0ubuntu1~22.04.2) 12.1 Copyright (C) 2022 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <https://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>.
For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from ./a.out... (gdb) l 1 #include <stdio.h> 2 #include <stdlib.h> 3 4 void main() 5 { 6 int *arr = NULL; 7 arr = (int*)malloc(10 * sizeof(int)); 8 int idx = 0; 9 for(idx = 0; idx < 10000; idx++) 10 arr[idx] = idx; (gdb) l 11 6 int *arr = NULL; 7 arr = (int*)malloc(10 * sizeof(int)); 8 int idx = 0; 9 for(idx = 0; idx < 10000; idx++) 10 arr[idx] = idx; 11 12printf("before\n"); 13 fflush(stdout); 14 15 free(arr); (gdb) b 12 Breakpoint 1 at 0x1201: file t2.c, line 12. (gdb) r Starting program: /home/minimonk/work/src/malloc/a.out [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Breakpoint 1, main () at t2.c:12 12 printf("before\n"); (gdb) print idx $1 = 10000 (gdb) n malloc(): corrupted top size
Program received signal SIGABRT, Aborted. __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737353705280) at ./nptl/pthread_kill.c:44 44 ./nptl/pthread_kill.c: 그런 파일이나 디렉터리가 없습니다.
그래서 printf / fflush 주석처리하고 free를 바로 브레이크 포인트 잡아서 해도 동일하게
루프 종료되면서 바로 에러가 나는 것 같기도...
15 free(arr); (gdb) c Continuing. malloc(): corrupted top size
Program received signal SIGABRT, Aborted. __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737353705280) at ./nptl/pthread_kill.c:44 44 ./nptl/pthread_kill.c: 그런 파일이나 디렉터리가 없습니다. (gdb)
