The Weird and The Wonderful

The Weird and The Wonderful forum is a place to post Coding Horrors, Worst Practices, and the occasional flash of brilliance.

We all come across code that simply boggles the mind. Lazy kludges, embarrassing mistakes, horrid workarounds and developers just not quite getting it. And then somedays we come across - or write - the truly sublime.

Post your Best, your worst, and your most interesting. But please - no programming questions . This forum is purely for amusement and discussions on code snippets. All actual programming questions will be removed.

Re: What the hell gcc?

Rick York18-Jun-24 4:53

Rick York

18-Jun-24 4:53

Visual C++ does not complain about anything with that code. I think this qualifies as a bug.

"They have a consciousness, they have a life, they have a soul! Damn you! Let the rabbits wear glasses! Save our brothers! Can I get an amen?"

Re: What the hell gcc?

honey the codewitch18-Jun-24 5:03

honey the codewitch

18-Jun-24 5:03

It very well could be. I've encountered this error in error before, I think?

I'm just really hesitant to file a bug against a compiler because I feel like they know a hell of a lot more about C and C++ than I do.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: What the hell gcc?

k505418-Jun-24 5:20

k5054

18-Jun-24 5:20

What machine are you targeting, and what are the sizes of float and long*?: If you compile this as 32 bit with gcc, you do not get any warnings.
Theory: you're compiling in 64 bit mode sizeof(float) = 4 and sizeof(long*) = 8. So what the compiler is trying to tell you is that long i = *(long*)&y the conversion of the float to a pointer, half the bytes are uninitialized. My theory anyway.

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Re: What the hell gcc?

honey the codewitch18-Jun-24 5:38

honey the codewitch

18-Jun-24 5:38

it's 32-bit GCC

My processor can handle 64-bit numbers, but not as a native word.

Edit: I'm not sure long isn't 64 bit on this platform, but I've always used long long for that.

My CPU will not handle 128-bit words under any circumstances.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: What the hell gcc?

k505418-Jun-24 5:47

k5054

18-Jun-24 5:47

The issue would arise if the size of a float is less than the size of a pointer. Maybe just ask the compiler to what sizeof(float) and sizeof(void*) return?

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Re: What the hell gcc?

honey the codewitch18-Jun-24 5:55

honey the codewitch

18-Jun-24 5:55

Thanks. I'll look into it as time and motivation allows. Smile | :)

Edit: Turns out i had a project open so it was easy enough to check

sizeof(float): 4
sizeof(long*): 4

I checked sizeof long* just to be certain

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: What the hell gcc?

k505418-Jun-24 6:43

k5054

18-Jun-24 6:43

Well, not that then Frown | :(

Seemed like a good answer at the time. Maybe it's just the type punning that's baffling the compiler?

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Re: What the hell gcc?

honey the codewitch18-Jun-24 6:48

honey the codewitch

18-Jun-24 6:48

That's my theory, but I'm uncomfortable with it if nothing else because

a) I hate assuming compiler bugs. So often it's some effing intricacy of the C or C++ language that is at play, rather than the compiler in error.

b) You'd think it would have been found and fixed. Like I said, this isn't the first time I've run into it. The last time was a lot more innocuous - no type aliasing or fudging like that. it was an enum struct type declared as a local variable and initialized at declaration time. Confused | :confused:

I'd dig up the old example if i could, but I ended up working around it in order to get the warnings out of my code without using compiler specific pragmas.

Edit: Duh. I am not using the latest GCC. I didn't think about that. Could easily be a bug.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

modified 18-Jun-24 13:52pm.

Re: What the hell gcc?

k505418-Jun-24 8:16

k5054

18-Jun-24 8:16

I get the same warning with gcc-14.1.0, and with x86-64 gcc-trunk over at the compiler explorer, so it's not been fixed so far.

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Re: What the hell gcc?

honey the codewitch18-Jun-24 8:21

honey the codewitch

18-Jun-24 8:21

I didn't think of trying godbolt. I'm really distracted rn on the phone w/ an old friend.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: What the hell gcc?

Rick York18-Jun-24 8:17

Rick York

18-Jun-24 8:17

As far as I am concerned, the fact that you have this line :

float y     = x;

which is clearly initializing the variable qualifies it as a bug. I can not conceive a situation where that is not a bug.

"They have a consciousness, they have a life, they have a soul! Damn you! Let the rabbits wear glasses! Save our brothers! Can I get an amen?"

Re: What the hell gcc?

0x01AA18-Jun-24 9:35

0x01AA

18-Jun-24 9:35

Quote:
I hate assuming compiler bugs

No, it is definitely not a compiler bug. It is a defined behaviour, there are lots of documents in www which explain the background.

Re: What the hell gcc?

honey the codewitch18-Jun-24 9:36

honey the codewitch

18-Jun-24 9:36

0x01AA wrote:
It is a defined behaviour

That's precisely what I was afraid of. Unsure | :~

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: What the hell gcc?

0x01AA18-Jun-24 9:45

0x01AA

18-Jun-24 9:45

In a message above, you mentioned, there is no std available. But maybe in your environement some kind of bit_cast is available?
If not, I think a similar behaviour (to inform the compiler [optimizer]) can be achived with reinterpret_cast, but at the moment I don't remember the document, from where I got this Frown | :(

Sorry, for my strange English ...

Re: What the hell gcc?

honey the codewitch18-Jun-24 9:46

honey the codewitch

18-Jun-24 9:46

It's possible I could do it with reinterpret_cast? I dunno

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: What the hell gcc?

0x01AA18-Jun-24 9:52

0x01AA

18-Jun-24 9:52

Try it

I think it simply informs the compiler 'you are aware' about a maybe not safe conversion ...

WTF-8

PIEBALDconsult17-Jun-24 18:40

PIEBALDconsult

17-Jun-24 18:40

Reviewing a CSV file today (which already has inconsistent quotes and such), I noticed it has a few characters (e.g. non-breaking space) encoded as UTF-8 -- fine, no big deal. But they still look odd after decoding... ah, they're encoded as UTF-8 twice... double-UTF-8. D'Oh! | :doh:

So now I have to write a recursive UTF-8 decoder... Sigh | :sigh:

Why doesn't .net simply do that to begin with? Mad | :mad:

<<== That's a rhetorical question.

It'll be breakfast at Milliways again.

Edit: 4/20 -- I have a working recursive UTF-8 decoding algorithm, in a custom decoder for a custom encoding (derived from the built-in UTF-8 encoding, so encoding should be as per normal).

What was unexpected was that the GetString method of the encoding didn't call the custom Decoder.
I just had a look at the refercence code GetString and I see:

// Returns a string containing the decoded representation of a range of
// bytes in a byte array.
//
// Internally we override this for performance
//
[Pure]
public virtual String GetString(byte[] bytes, int index, int count)
{
    return new String(GetChars(bytes, index, count));
}

Does that mean that it doesn't actually use my decoder?
Shouldn't it call GetDecoder() and use that decoder?
(I'm not experienced at reading the reference source.)
I'll get back to it on Monday.

Edit: 4/21 -- Reading some more about UTF-8 on the 'pedia, I see:

The Unicode Standard requires decoders to
"... treat any ill-formed code unit sequence as an error condition. This guarantees that it will neither interpret nor emit an ill-formed code unit sequence."

and

The standard also recommends replacing each error with the replacement character "�" (U+FFFD).

Which I choose not to do...

These recommendations are not often followed.

But it makes me think that the few U+FFFD characters I see in the file may have begun as unencoded characters which were errantly read with a UTF-8 decoder. Which means that the file I have is in even worse condition than I thought.
Anyway, my current decoder is quite permissive in what it accepts -- preferring not to throw exceptions, but rather pass any errant bytes along to the caller. I will likely alter that next week.

Edit: 4/22 -- A rough logic diagram of my algorithm.

         --------------------------------------------------------------------
         | My custom Decoder                                                |
         |                                                                  |
bytes ---------> Is UTF-8 encoded multi-byte?---NO----------------------------- chars -->
         |   ^                              |                               |
         |   |                              |    --------------------       |
         |   |                              |    |                  |       |
         |   |                              YES----> UTF-8 decoder ----V    |
         |   |                                   |__________________|  |    |
         |   |                                                         |    |
         |   ^---------------------------------------------------------<    |
         |                                                                  |
         |__________________________________________________________________|

The thing to remember is that the UTF-8 Decoder will only ever be presented with byte sequences which are (or appear to be) valid UTF-8 encoded multi-byte characters. Anything else is passed along unchanged, this includes single-byte UTF-8 encoded characters.

I may need to implement a UTF-8 Encoder which won't double-encode UTF-8 characters.

modified 22-Jun-24 13:46pm.

Re: WTF-8

Peter_in_278017-Jun-24 19:09

Peter_in_2780

17-Jun-24 19:09

I got a phishing email the other day.
Embedded HTML to imitate a Micro$oft login form (posting credentials to evil.org of course).
Inline base-64 encoded, easy peasy.
%-encoded inside that. One and a half times....
The outer decode works, but still got %'s in there.
Decode again and *barf*, it's broken (but only in some places).
Wasn't game to see what a browser would make of it.
Given browsers' general tolerance of coding errors, I suspect it might just have worked.

Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

Re: WTF-8

honey the codewitch17-Jun-24 21:16

honey the codewitch

17-Jun-24 21:16

.NET doesn't do that to begin with because it wouldn't make any sense.

The problem is your CSV has bad encoding.

What you wrote is a workaround for a poorly encoded file.

That's not .NET's business, and frankly, if it did that, it would be a Bad Thing(TM)

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: WTF-8

PIEBALDconsult18-Jun-24 3:01

PIEBALDconsult

18-Jun-24 3:01

Oh, I know. Yet why not have an option? As when getting a directory listing, you can specify TopDirectoryOnly or AllDirectories. Not that they would have expected this to be needed twenty years ago.

What I have so far will deal with double-encoding, but I can imagine the rabbit hole going deeper. All the way to the turtles I'm sure.
Anyway, it's a good exercise.

Re: WTF-8

honey the codewitch18-Jun-24 4:15

honey the codewitch

18-Jun-24 4:15

Because in the decades that UTF-8 is available you're the second person to need the feature.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: WTF-8

PIEBALDconsult18-Jun-24 14:07

PIEBALDconsult

18-Jun-24 14:07

Probably the first. The other guy on the team hadn't noticed the issue.

Re: WTF-8

honey the codewitch18-Jun-24 6:01

honey the codewitch

18-Jun-24 6:01

Adding, there's another issue.

What if your intent was to embed control characters into UTF-8?

.NET cannot do this for you without breaking the UTF-8 spec.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

Re: WTF-8

PIEBALDconsult18-Jun-24 14:10

PIEBALDconsult

18-Jun-24 14:10

For instance?

honey the codewitch wrote:
.NET cannot do this for you

Bet it can. Cool | :cool:

Re: WTF-8

honey the codewitch18-Jun-24 15:01

honey the codewitch

18-Jun-24 15:01

Yeah Microsoft could break UTF8 to make you happy and make everyone else mad.

And make .NET broken.

I'll get back to you when someone besides you thinks this is a good idea.

Check out my IoT graphics library here:
https://honeythecodewitch.com/gfx
And my IoT UI/User Experience library here:
https://honeythecodewitch.com/uix

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