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As per Jeff's suggestion in this comment:

You can use this question as a formatting sandbox. You can

  • edit this question itself (Community Wiki questions such as this one require 100 reputation to edit)
  • post answers to this question (Since this question is protected, this requires earning 10 reputation on this site)
  • post comments to this question or its answers
  • test suspected bugs with the editor

Beware that since the changes to syntax highlighting in December 2010, and the inline hints added March 2011, no syntax highlighting is applied unless the question's tags or an inline hint enable it. So, to test highlighting here in the sandbox:

  1. On the start of a line, specify a language inline using <!-- language: lang --> hints, and indent the code 4 spaces as usual. There is a full list of hints (scroll down a little).

    <!-- language: lang-html -->
        While not hinted otherwise: <html></html> source <b>goes</b> "here".
    <!-- language: lang-js -->
        var a = 3;
        while (not (a > 0)) {
            alert("JavaScript code <b>goes</b> here.");
  2. Or:

    • Save your post.

    • Use something like Firebug (Firefox), Web Inspector (Safari, Chrome) or Developer Tools (Internet Explorer 8) to edit the resulting HTML. To open Chrome Dev Tools, press F12

    • Find the <pre> element and add the attribute class="prettyprint", or change it into something more specific, like class="lang-vb prettyprint".

    • Run the following in the location bar: javascript:prettyPrint();

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Please provide an MCVE. – Kevin Jul 24 '15 at 13:41
Questions about underwater basket weaving are off-topic for this site. – Kevin Jul 24 '15 at 14:42
@humn instead of a rollback, you can perform an edit with the exact same contents as before your edit (title, in your case) and assuming you do it within the 5 minutes grace period, it will show only a single revision with "[Edit removed during grace period]" - instead of having two revisions. – Shadow Wizard Apr 10 at 10:12

394 Answers 394

Test for edit comment within first grace period.

Edit 1, with edit summary
Edit 2, with edit summary
Edit 3, no edit summary
Edit 4, with edit summary
Edit 5, with edit summary
Edit 6, after 9 minutes, with edit summary
Edit 7, after 9 minutes, with edit summary, overwriting previous summary
Edit 8, after 10 minutes, no edit summary

Editing within grace period no longer remembers previous edit reason?

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Tabs FTW

And this is just some padding text so I can actually answer.

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This is a test of a broken hyperlink:

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Testing to see if equations (TeX) are supported using any of the longhand environments:

[ x^2 ]

$$ x^2 $$

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Trying to figure out the proper way to format italic_NONITALICFORWARDSLASH_italic with no spaces:

*macro*/*conditional* - macro/conditional
*macro*\/*conditional* - macro/*conditional*
*macro*//*conditional* - macro//conditional
**macro*/*conditional** - macro*/*conditional

This is already done here:
You need HTML-formatting <i></i> or <b></b>
<i>macro</i>/<i>conditional</i> - macro/conditional

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<table>attempting to inject a *not supported tag</table>

<p>or an allowed one?</p>


edit: it is pointless, they are escaping &lt; and &gt; correctly

but well, I managed to find a way to prevent them to stripe off non supported tags :)

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On my E8200 box this doesn't occur, but on my Atom N450 netbook (both running OpenSuse 11.2), whenever I read the CPU's TSC, the returned value is mod 10 == 0, i. e. it is without remainder divisible by 10. I'm using the RDTSC value for measuring times that interesting pieces of code take, but for the purpose of demonstration I've made up this little program:

        .global _start

_start: xorl    %ebx,%ebx
        xorl    %ecx,%ecx
        xorl    %r14d,%r14d
        movb    $10,%cl
loop:   xchgq   %rcx,%r15          # save to reg
        shlq    $32,%rdx
        xorq    %rax,%rdx          # full 64 but of RDTSC
        movq    %r14,%r13          # save the old value
        movq    %rdx,%r14          # copy current
        movq    %r14,%rsi          #  argv[1] of printf()
        subq    %r13,%rdx          #  argv[2] (delta)
        leaq    format(%rip),%rdi  #  argv[0]
        xorl    %eax,%eax          #  no stack varargs
        call    printf
        xchgq   %rcx,%r15
        loop    loop

0:      xorl    %eax,%eax
        movb    $0x3c,%al

        .size   _start, .-_start

format: .asciz     "rdtsc: %#018llx = %1$llu -- delta: %llu\n"

(I usually use my own routines for converting, but to prevent readers from suggesting that the error might be there, I'm just using printf() here.)

With the above code, the output is (for example):

rdtsc: 0x000b88ef933ffd06 = 3246787292822790 -- delta: 3246787292822790
rdtsc: 0x000b88ef9342fcf4 = 3246787293019380 -- delta: 196590
rdtsc: 0x000b88ef93435dca = 3246787293044170 -- delta: 24790
rdtsc: 0x000b88ef9343b43c = 3246787293066300 -- delta: 22130
rdtsc: 0x000b88ef93440c34 = 3246787293088820 -- delta: 22520
rdtsc: 0x000b88ef9344604e = 3246787293110350 -- delta: 21530
rdtsc: 0x000b88ef9344b4d6 = 3246787293131990 -- delta: 21640
rdtsc: 0x000b88ef9345085a = 3246787293153370 -- delta: 21380
rdtsc: 0x000b88ef93455d96 = 3246787293175190 -- delta: 21820
rdtsc: 0x000b88ef9345b16a = 3246787293196650 -- delta: 21460

As can be easily seen, the delta varies in reasonable amounts. But conspicuous (not to say conspired ;-) is that the least significant decimal digit is always 0.

I've observed this phenomenon for more than two years now, and is not the first address where I make this issue public. But nowhere I got a reasonable answer yet. The ideas we (me and other people out there) came up with, are that

  • the TSC is incremented only every 10th cycle, but then by 10, or
  • the TSC is internally updated correctly, but reflected to the outside only every 10th cycle, or
  • the TSC is incremented by 10 each cycle.

None of these points really make sense, however. I should have actually run a program like that on the E8200 (which is currently out of order) to see if the order of magnitude of the deltas is the same or only a tenth of those in the above output. (Any volunteers?)

Googling didn't help, Intel's manuals did neither.

When discussing with other people, there was no-one else who experienced the same behaviour. If it had to do with the kernel, then at least 3 versions were affected, but then... what does the kernel have to do with it?

I've also had the netbook in service, and it came back with a new motherboard — implied a new CPU, so at least two individual entities of N450 must be affected.

I've also took measures against clock frequency changes (and no matter what frequency I fixed the clock to, the values varied only in the expected range (the same as shown)), and switched off HT, though these should actually help to get some other least significand digits, rather than preventing them. But just to be sure.

Well, if anyone wants to run the program on their machine, the command line is (provided you save the source in a file rdtsc.s):

as rdtsc.s -o rdtsc.o
ld --dynamic-linker=/lib64/ rdtsc.o -L /lib64 -l c -o rdtsc

In order to build it with the gcc frontend, i. e.

gcc -l c rdtsc.s -o rdtsc

you must add (or replace the _start: label with) a main: label and make it global.

share|improve this answer
#include <unordered_map>

int main() {
    std::unordered_map<int,int> m;

Testing two edits without a second edit summary. This is the first edit. This is the second edit. A third unsummarised edit.

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Bold text = Bold text and Italic text = Italic text or Italic text = Italic text – TheLQ Jun 30 '10 at 19:15

And this is a...


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Multi-line spoiler:

Spoiler line 1 (note the two spaces at the end of this line and the next)

Spoiler line 2

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URLs cannot contain parentheses?

Is it the space?

It works with urlencode though

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testing slashes escaping in backticks code in answers \, \\ and \a, \\a

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this is
a test


this is a test

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Testing markdown. Thanks Arjan

valid XHTML



Oh gee look, you can so too underline in Stack Exchange sites:

 ̲u̲n̲d̲e̲r̲l̲i̲n̲e̲ ̲


 ̳u̳n̳d̳e̳r̳l̳i̳n̳e̳ ̳

  ̲̅M̲̅C̲̅M̲̅X̲̅C̲̅I̲̅X̲̅ ̲̅

  ̲̅m̲̅c̲̅m̲̅x̲̅c̲̅i̲̅x̲̅ ̲̅
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share|improve this answer
​​​​​​​​​​​​​​​ – brasofilo Sep 10 '13 at 23:29

Mouse over the left of the tower of hello

Yay you can follow instructions hello

Apparently <kbd> is immune to spoilers


hi again

hi yet again


why is this text drifting out


! spoilers don't work now?

! hey that's messed up

now they do?!?!

share|improve this answer

I've always wondered how to put a backtick in a backtick, now I know. Use 2 backticks as delimiters. ``.

SELECT `a` from `table` where `b`=`c`;

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Documented here, Rocket. – Arjan Feb 4 '13 at 17:52
starts with codez

w00t woot

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<pre><code> has highlighting too:

Look ma, <em style="xyz">highlighting<em>!
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what is this magic dust that causes things to appear

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Some code formatting for testing of the problem outlined here: What is Wrong with Code Formatting.

asyncTask.ContinueWith(task =>
    // Check task status.
    switch (task.Status)
        // Handle any exceptions to prevent UnobservedTaskException.             
        case TaskStatus.RanToCompletion:
            if (asyncTask.Result)
                // Do stuff...
        case TaskStatus.Faulted:
            if (task.Exception != null)
                mainForm.progressRightLabelText = task.Exception.InnerException.Message;
                mainForm.progressRightLabelText = "Operation failed!";

This does not format correctly.

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Just testing:

Code formatting doesn't work well with NO-BREAK SPACE

-38 y1  +  35 y2  +  31 y3  = -3047

  11 y1 + -13 y2 + -34 y3 = 784

  34 y1 + -21 y2 + 19 y3 = 2949

But works with space (ASCII 32)

-38 y1  +  35 y2  +  31 y3  = -3047

11 y1  + -13 y2  + -34 y3  = 784

34 y1  + -21 y2  +  19 y3  = 2949
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protected by Oded Nov 17 '14 at 15:36

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