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How to automatically generate a stacktrace when my program crashes
...nclude <unistd.h>
void handler(int sig) {
void *array[10];
size_t size;
// get void*'s for all entries on the stack
size = backtrace(array, 10);
// print out all the frames to stderr
fprintf(stderr, "Error: signal %d:\n", sig);
backtrace_symbols_fd(array, size, STDERR_FILENO)...
Does C have a “foreach” loop construct?
...ave a foreach, but macros are frequently used to emulate that:
#define for_each_item(item, list) \
for(T * item = list->head; item != NULL; item = item->next)
And can be used like
for_each_item(i, processes) {
i->wakeup();
}
Iteration over an array is also possible:
#define f...
Header files for x86 SIMD intrinsics
.../x86-64 use x86intrin.h
For gcc/clang/armcc targeting ARM with NEON use arm_neon.h
For gcc/clang/armcc targeting ARM with WMMX use mmintrin.h
For gcc/clang/xlcc targeting PowerPC with VMX (aka Altivec) and/or VSX use altivec.h
For gcc/clang targeting PowerPC with SPE use spe.h
You can handle all t...
PHP function overloading
...c function that takes in a variable number of arguments. You would use func_num_args() and func_get_arg() to get the arguments passed, and use them normally.
For example:
function myFunc() {
for ($i = 0; $i < func_num_args(); $i++) {
printf("Argument %d: %s\n", $i, func_get_arg($i))...
How to validate an e-mail address in swift?
...
I would use NSPredicate:
func isValidEmail(_ email: String) -> Bool {
let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"
let emailPred = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
return emailPred.evaluate(with: email)
...
mongodb group values by multiple fields
...tems to $push to an array.
db.books.aggregate([
{ "$group": {
"_id": {
"addr": "$addr",
"book": "$book"
},
"bookCount": { "$sum": 1 }
}},
{ "$group": {
"_id": "$_id.addr",
"books": {
"$push": {
...
How to find the size of localStorage
...
Execute this snippet in JavaScript console (one line version):
var _lsTotal=0,_xLen,_x;for(_x in localStorage){ if(!localStorage.hasOwnProperty(_x)){continue;} _xLen= ((localStorage[_x].length + _x.length)* 2);_lsTotal+=_xLen; console.log(_x.substr(0,50)+" = "+ (_xLen/1024).toFixed(2)+" KB")...
Lua简明教程 - 脚本技术 - 清泛IT论坛，有思想、有深度
...ble来管理全局变量的，Lua把这些全局变量放在了一个叫“_G”的Table里。我们可以用如下的方式来访问一个全局变量（假设我们这个全局变量名叫globalVar）：_G.globalVar
_G["globalVar"]复制代码
我们可以通过下面的方式来遍历...
How do I detect a click outside an element?
...')
.find('a:first')
.focus();
e.preventDefault();
}
$('.menu__link').on({
click: function (e) {
$(this.hash)
.toggleClass('submenu--active')
.find('a:first')
.focus();
e.preventDefault();
},
focusout: function () {
$(this.hash).data('submenuTimer', ...
Python, creating objects
... ""
# The class "constructor" - It's actually an initializer
def __init__(self, name, age, major):
self.name = name
self.age = age
self.major = major
def make_student(name, age, major):
student = Student(name, age, major)
return student
Note that even tho...