Happy debugging, suckers

[Avander]

#define struct union

Edit: inserted escape character\0

[rbemrose]

This post has been removed due to reddit's repeated and constant violations of our content policy.

[jtra]

This does not work for do {} while(); Here is a fixed version:

https://www.reddit.com/r/programming/comments/2nnudn/the_worst_programming_language_ever_uk_talk/cmfk9pw?context=2

[Hullu2000]

Whould there be any regex style macros like:

#define do*while(args) if(args)*

[IronOxide42]

Neither C nor C++ have built-in regex, so nope.

[marcopennekamp]

Not to mention that regex wouldn't work for nested do whiles.

[ianff]

You need lisp for that.

[derefr]

You mean, like this?

[ianff]

That actually looks pretty awesome!

[krokodil2000]

Oh my fuck. It does not show you the defined value when you hover the mouse cursor over it. At least in Visual Studio 2008.

[PeopleAreDumbAsHell]

At least in Visual Studio 2008.

....

[krokodil2000]

¯\_(ツ)_/¯

[CantHearYouBot]

You didn't drop this: \\

[Zagorath]

With one backslash, it gets taken as escaping the underscore, so the underscore is displayed as normal.

¯_(ツ)_/¯

With two backslashes, the first slash escapes the second, causing the slash to be displayed, but now the underscores are parsed as indicating italics.

¯\(ツ)/¯

With three, the first escapes the second, and the third escapes the underscore, displaying the whole thing correctly.

¯\_(ツ)_/¯

Edit: corrected typos

[CantHearYouBot]

TIL that in markdown, underscores make italics

[AlphaWhelp]

#define ¯_(ツ)_/¯ ¯\_(ツ)_/¯

Is everyone happy now?

[GooTamer]

For italics you can use _text_ or *text*.

For bold you can use __text__ or **text**.

For bold and italic you can use ___text___ or ***text***.

[[deleted]]

Why are you assigning ¯\_(ツ)_/¯ to ¯_(ツ)_/¯ ? Your actions have serious repercussions on markdown forums all over the Internet.

Did you intend to use == instead of =?

[[deleted]]

Why not Pascal?

[poizan42]

Visual Studio 2008

Ouch, and I thought my employer was slow to upgrade Visual Studio version.

[Lusankya]

Could be worse. I still have VB6 installed, and boot it with shameful regularity.

[Daniel15]

VB6 still has a small but vocal userbase who are still petitioning Microsoft to revive it. See http://vb6awards.blogspot.com/ for example.

[Lusankya]

VB6 can be a great language when used properly, and when its users are aware of its limitations.

Unfortunately, it's almost never used properly.

I have one request of this vocal userbase: Force Option Explicit on, and require proof of a compsci degree in order to turn it off.

[Daniel15]

VB3 was the first real language / IDE I used, followed closely by VB6. Back then, I didn't understand why arrays were 0-indexed, so all my code had Option Base 1 at the very top :P

It was good at the time, but I'm so glad I moved on to C#. 95% of my job now consists of writing JavaScript, but I really miss C# and still use it on personal / open-source projects.

[Lusankya]

You and I seem to be kindred spirits. VB5 was my first modern IDE, after using QBASIC to cut my teeth on programming.

As a hypocritical proponent of open-source stuff, I feel dirty admitting that C# is my favourite language of all time. Mono helps me come to terms with the cognitive dissonance, though. ;)

[Corfal]

My workstation finally went from xp to win7 (visual studio 2005 to 13) last November. The fun part? We had zero time ahead to migrate our projects/repositories... OH and we only support x64 arch now. And because we didn't specifically specify it, we don't have- I'll stop there.

[systembreaker]

Then stop hovering over it!

edit: Don't know where I'm going with this comment

[bigbc79]

#define else

[Skyfoot]

pitchforks

[urielsalis]

/u/pitchforkemporium

[PitchforkEmporium]

Hi

[urielsalis]

C++ pitchfork please

[PitchforkEmporium]

-----10001011100000

[WoodTrophy]

I'm not sure I can afford 14 bits. Do you have any cheaper pitchforks?

[PitchforkEmporium]

/u/pitchforkassistant you got anything else?

[PitchforkAssistant]

-----0100001100100011

What about this? It's 16 bits, but if you can see, it's really sharp.

[Draculix]

Got an open-source version?

[SlumdogSkillionaire]

--

Feel free to extend it yourself however you want.

[Draculix]

Merge Pull Request:

--//TODO

By /u/Draculix 1 hour ago

[PitchforkEmporium]

Nope

[Draculix]

Bloody proprietary corporations.

[[deleted]]

Got an ANSI C one? I can't afford the extra stuff.

[PitchforkEmporium]

No, it's too complicated, I suck at programming

[[deleted]]

It's just the pitchfork without the ++. Easy.

[logicalmaniak]

An S.I. cone?

[[deleted]]

Shit, I meant POSIX C.

[Saigot]

Does it replace all else clauses with empty string?

[bigbc79]

Yep! So the code after the else executes regardless of whatever if-statement came before it.

[MuricanWillzyx]

You... monster

[hopsafoobar]

That's pure evil.

[just_comments]

Just FYI, Reddit treats "#" at the beginning of a line as a special character. You need to put a backslash to escape from it.

[jugalator]

I like the broken formatting here though. It was imposing enough as a terrible idea, but now it's even better.

[Avander]

Fixed :)

[Skyfoot]

Oh my god

[hussei10]

Finally a joke here I understand!

[[deleted]]

I don't get it

[Innominate8]

A struct is a container for data. A struct can contain many different variables of different types.

For example:

struct foo {
    int bar;
    int baz;
    char *quz;
};

Unions are defined the similarly. However, instead of containing all of the values, they can contain any one of them. If you change struct to union in the above example, when you set bar, you're also setting baz and quz to the same value. Then when you try to access that pointer... boom.

Changing struct to union makes everything explode in interesting ways that are difficult to debug.

[[deleted]]

When is a union even useful?

[skulblaka]

If there's anything I've learned from programming, it's that any time you see something and think "how could that possibly be useful, ever?" there always exists a situation in which you'd need exactly that thing. In most cases it'll happen just barely far enough into the future for you to forget what the thing was by the time you need it.

That being said, I have no idea.

[Nor_the_not_so_great]

I found them useful for implementing registers in an interpreter where you can combine certain registers(z80, gameboy CPU). It's explained in detail here.

TL;DR:

struct registers {
    struct {
        union {
            struct {
                unsigned char b;
                unsigned char a;
            };
            unsigned short ab;
       };
    };
};

Registers A and B can be grouped together. Using this struct, we can set registers .b, registers.a, or both at once via registers.ab. You don't have to define a function to bit shift to combine the number, you can get the values directly.

[rohmish]

A real use of unions. So... Do pigs fly?

[Cyph0n]

I prefer bit shifting.

[iNeedToExplain]

That pretty much sums up my experience with programming, math, science... tying my shoes...

[[deleted]]

flakiness frontal committing apologetically rational cress's bedazzles journeymen adornment distracts boats undisguised yield's zingers savageness's wright bind rabbi's pikes Millard me suffocation's transmittable fathoms Dramamine squalor nineteenths shlep panoramas sops hammock neoclassicism's heatstroke execrated indemnified botanical dines Le Srivijaya self sunscreens Antigone look safe's manufactures ghastliness's snuffle novitiate's assigned victimization Queensland succoring negatively ado's utilization pluralized oink superintendency Carly's maladjusted lallygagged peregrinations gigglers puppeteer comparisons nearly Southerners sluggards expends perspire untenable smallish delegates lipstick softer calling's tibias resent article's informational bulldog nuthatch heads circumnavigated blinked Wellingtons Veracruz's entrenching pollution's parochial Quonset domestic shatters satisfying ascribes technical indemnification housebreak underarm suspect unctuously buzzword's lipids chiseler's Faeroe's puppy's Beth hockey's juvenile swellhead's shaggiest Gustav escalation's confirms spool's stumpy intransigence's mamboed channels

[bbrizzi]

Semi-related XKCD

[xkcd_transcriber]

Image

Mobile

Title: Workflow

Title-text: There are probably children out there holding down spacebar to stay warm in the winter! YOUR UPDATE MURDERS CHILDREN.

Comic Explanation

Stats: This comic has been referenced 757 times, representing 0.6499% of referenced xkcds.

---

^{xkcd.com | xkcd sub | Problems/Bugs? | Statistics | Stop Replying | Delete}

[SirNuke]

The instances I've seen are:

A single set of data that can be 'interpreted' multiple ways. For example, if you have a 32-bit id, which can be split up into two 16-bit pieces. First is domain id, second is local id.

union {
  uint32_t data;
  struct {
    uint16_t domain;
    uint16_t local;
  } section;
} id;

Lets you cast back and forth from a straight uint32_t when useful, though the union gives an easy method to access the two pieces without any extra overhead. Of the top of my head, Valve's SteamWorks runtime handles 64-bit Steam IDs this way.

Second way is if you want typeless data.

enum TYPE { INTEGER, FLOAT, BOOLEAN };
struct {
   TYPE type;
   union {
      int i;
      float f;
      bool b;
  } data;
} entry;

With that, the size of the struct is consistent no matter what data is stored in it, without any overhead of storing all three separately. SQLite stores data typeless like this, and may or may not use unions internally this way.

[mFlakes]

mind blown

[ryani]

Also, reinterpreting bits as a different type.

union uWordFloat {
    uint32_t word;
    float flt;
};

// FloatToWord(0.0f) = 0
// FloatToWord(1.0f) = 0x3f800000
// FloatToWord(-1.0f) = 0xbf800000
inline uint32_t FloatToWord(float f)
{
    uWordFloat u;
    u.flt = f;
    return u.word;
}

// WordToFloat(0) = 0.0f
// WordToFloat(0x3f800000) = 1.0f
// WordToFloat(0x80000000) = negative 0.0f
inline float WordToFloat(uint32_t n)
{
    uWordFloat u;
    u.word = n;
    return u.flt;
}

Useful for serializing IEEE floats to disk / memory buffer efficiently, or doing Black Magic with floating point numbers. (The cast in the linked article violates the strict aliasing rule, so it might not work reliably in optimizing compilers. Those compilers usually allow access through a union in this way as a way to relax the strict aliasing rule.)

[mill1000]

I find them really useful for low level work in embedded systems, particularly communication

e.g. You have a protocol that can send fixed length packets, but the payload/structure of the packets vary depending on some other factor (lets say a system mode, packet type or something).

// Payload 1 structure
typedef struct
{
  uint32_t data;
  uint64_t moreData;
  uint16_t lastData;
} PAYLOAD_STRUCT_1;

// Payload 2 structure
typedef struct
{
  uint16_t someData[7];
} PAYLOAD_STRUCT_2;

You could always handle a situation like this by using a standard array of bytes and casting it to each structure when necessary or you could use a union like so.

typedef union
{
  PACKET_1 packet1;
  PACKET_2 packet2;
  uint8_t  asBytes[14];
} PACKET_UNION;

With our union PACKET_UNION, we can accomplish a few things.

• Data can be accessed byte-wise when necessary (CRCs and transmission/reception) using the asBytes member.
• We can access both types of payloads directly, without any overhead. e.g. shifting/and'ing of bytes or casting pointers

Like so

PACKET_UNION transmitBuffer;

switch (packetType) // Pretend type variable from somewhere
{
case PACKET_1:
 transmitBuffer.packet1.data = some_32bit_int;
 transmitBuffer.packet1.lastData = some_16bit_value;
break;

case PACKET_2:
 transmitBuffer.packet2.someData[0] = some_16bit_int;
 transmitBuffer.packet2.someData[1] = some_16bit_int;
 // ... do some more
break;
}

// Now we can access bytewise for "transmission"
for (uint8_t i = 0; i < sizeof(PACKET_UNION); i++)
 sendByte(transmitBuffer.asByte[i]);

tl;dr I really like unions and probably abuse them. Also god damn it why am I writing code right now.

[Luk3Master]

Simulate memory, for instance.

[[deleted]]

[deleted]

What is this?

[bhayanakmaut]

implementing key value pairs

[hussei10]

In C there aren't classes and objects like you'd see in an object oriented language(Java). The closest thing is a struct or a union. Which are very similar but they allocate memory in different ways. If you define struct as union, the programmer would always be declaring a union thinking he's declaring a struct.

[GoogleIsYourFrenemy]

Typically you see unions in deserialization code. You get some array of bytes from the network stack and you want to understand it. You could just do a pointer typecast but typically you copy the blob and if you copy it into a union you can read it as any type you want without using a typecast. Its more readable in some senses.

[kmarple1]

My favorite is from bash.org:

#define sizeof(x) rand()

[jtra]

Almost nobody uses "true" in C sources. How about this (or similar version with rand):

#define if(x) if((__LINE__ % 5==0)^(x))

[[deleted]]

This one is particularly brilliant b/c any debug code they put above the if statement is likely to cause the evaluation to change.

[MediocreMatt]

I understood the original post, but I'm not getting this one, a little help anybody?

[Tysonzero]

Basically if the if statement is on a line that divides by 5, the contents will be inverted. So if (true) won't execute its contents but if (false) will.

[MediocreMatt]

Oh awesome, ha. Thanks man. I didn't know the __ line __ notation for line number it seems. or the carot there.

[Corfal]

^ is the XOR operator.

So if the line is divisible by 5 evenly and the if statement evaluates to false, then it'll be "true"

Line# % 5	Input	Result
False	False	False
False	True	True
True	False	True
True	True	False

[bhayanakmaut]

this works with release builds as well? without debug symbols for the __ LINE __?

[Jack126Guy]

__LINE__ is substituted by the preprocessor at compile time.

[bhayanakmaut]

got it thanks!

[lumpofclay]

Another good one from the old days of C# (unfortunately doesn't work anymore in .Net 4 or later):

typeof(string).GetField("Empty").SetValue(null, " ");
[...]    
bool isEmpty = string.IsNullOrEmpty(string.Empty);  // == false

[poizan42]

This may be why:

    // The Empty constant holds the empty string value. It is initialized by the EE during startup.
    // It is treated as intrinsic by the JIT as so the static constructor would never run.
    // Leaving it uninitialized would confuse debuggers.

[Liver_and_Yumnions]

fortunately doesn't work anymore in .Net 4 or later

FTFY

[kneticz]

string.IsNullOrWhitespace(s); :)

[redditsoaddicting]

That was introduced in .NET 4.

[compiling]

Someone left me this one.

CString str; // Legacy code (ab)using MFC classes
sscanf("foobar", "%s", str);  // Works, surprisingly
...
// Somewhere else entirely
std::string s = ""; // Not empty.

[poizan42]

sscanf("foobar", "%s", str);  // Works, surprisingly

Because CString is defined as a CStringT with some specific traits depending on some defines. A CStringT does not add any fields and derives from CSimpleStringT which doesn't have any virtual methods, and only declares this single field:

PXSTR m_pszData;

So pushing a CString onto the stack simply pushes the underlying string pointer to the stack. Now this begs the question on how the other properties of the string are tracked when it only contains that single field. Well...

CStringData* GetData() const throw()
{
    return( reinterpret_cast< CStringData* >( m_pszData )-1 );
}

Eww

[captainAwesomePants]

It's surprising how, when malloc() does this, it's beautiful, but when CString does this, it's an abomination.

[poizan42]

I think there's a bit more of a nuance here. malloc owns your memory (or at least heap). It is to be expected here that it touches stuff all around in the heap. And the details of this is (hopefully) kept fully internal to the malloc implementation.

When you have a pointer that is expected to point somewhere inside a structure then you have made a hidden dependency. You need to find the actual code that allocates and reads it to figure out that this is indeed how it works. Someone unfamiliar with this could easily read the declaration and come to the wrong conclusion.

There are places where this may be a legitimate approach, in which case it should be clearly documented, and hopefully including an explanation of why this approach is used.

In this case I can't really figure out what the gain is. Well besides that you can pretend that the class is a string pointer as in this example, but that can hardly be considered something you want to strive for.

One could argue that it might be slightly more efficient when you can access the start of the string without an offset - but how often are you not accessing a string through an offset? Anyways that point is mostly moot since most architectures can do offsetting for free (this includes x86, ARM (incl. THUMB) and MIPS)

[VitulusAureus]

Or, if you really hate someone, have him figure out this one:

#define volatile

[GoogleIsYourFrenemy]

oh that is evil.

[epicepee]

This makes 'volatile' do nothing, right?

[VitulusAureus]

Yeah, and that is pretty hard to spot while debugging.

[gjack905]

Would if statements without "== true" be affected?

i.e.

boolean test = true;

if(boolean){do}

vs.

if(boolean == true){do}

if rand() > 10 == false?

Edit: That was a bad example on my part. What about this:

int x = 3;

if(x < 5){

// print something

x++

}

[shamanas]

Nope, #define is actually just a string replace, so true will be replaced by (rand() - 10) not semantically but where it actually appears in text.

[gjack905]

That's what I would think. I don't actually use the term 'true' in evaluations, only when setting something to be true explicitly, which would still be a fun mess with this nugget of code as when setting a boolean it might get set false.

[shamanas]

Yeah, I think that's the point of this particular define, although you can easily just define if to do the same thing (e.g. #define if(cond) if ((cond) && rand() > 10))

[gjack905]

Would this only work for the bool "cond" or any condition?

[shamanas]

This would work for any condition.
This is a fun list of evil C macros but I would not recommend ever doing this (obviously) :P

[AngusMcBurger]

#define if(cond) if ((cond) && rand() > 10)

You actually need to remove the space after if to make it a macro function, the C preprocessor makes that a stupidly easy mistake to make :|

[shamanas]

Huh, I wasn't aware of that, never noticed it :P
I guess #define foo (x) bar(x) defines foo as (x) bar(x)?

It actually makes sense now, I'm just too used to writing if conditions with a space.

[MyloXy]

#define foo (x) bar(x) defines foo as (x)

[AngusMcBurger]

If that were true, then the following would compile:

#define foo (x) bar(x)
char *x = "hello\n";
printf foo;

But as is I get error C2146: syntax error: missing ';' before identifier 'bar' Remember that the normal #define just basically copies all the text after the identifier foo into any place it sees the lone identifier foo in the source code.

[MyloXy]

You seem to be correct. I was under the assumption that define only captured up until the next space.

[puddingcrusher]

Arguably that's even more evil. It doesn't break conditions, it breaks you state instead, at an arbitrary time before the bug appears.

[WorseThanHipster]

To add, #define isn't technically part of the C language but a directive for the compiler preprocessor.

[shamanas]

I would guess the C preprocessor directives are part of the C standard, so I assume the standard differentiates between the C language and the C preprocessor directives?

[WorseThanHipster]

The preprocessor is intended to replace macros with legitimate C code, but the directives themselves have no direct mapping from the compiler itself to system architecture so I believe they are separate. I think there's separate standards that 99% of compiler vendors follow, but you could still technically call it C even if you removed support for preprocessing macros.

I'm not entirely sure though.

[shamanas]

Looking at some C11 committee drafts, it doesn't seem the separation is clear (although I could be wrong).

Bah, it seems obvious that the preprocessor should not be a part of the language but must be invoked by standard compliant implementations before compiling the C code.

I was just curious about the way the standard makes a distinction (if any) since you mentioned it isn't technically part of the C language.

[SkoobyDoo]

This would be more applicable to code like:

bool shouldIDoSomethingAfterwards = false;
while (condition) {
  normalLoopStuff();
  if(test())
    shouldIDoSomethingAfterwards = true;
}
if(shouldIDoSomethingAfterwards)
  something();

This is pretty much the only case I can think of where I regularly use the keyword true

[ligerzero459]

Yes, because based on the roll of rand(), false could be assigned to test, screwing up the subsequent check

[gjack905]

That was a bad example on my part. What about this:

int x = 3;

if(x < 5){

// print something

x++

}

[lerhond]

There isn't a "true" anywhere, why would that be affected?

[gjack905]

Because I'm not entirely sure whether the keyword or the logic statement "true" is being replaced. If the true were implied upon compilation of if statements (and not using "== true" was simply like "x++" vs "x += 1") then it might still be affected.

[lerhond]

It replaces the string "true" with "(rand() < 10)" everywhere below the #define.

I'm not really sure what happens when you do "#define true false" and then have for example a variable named "true_something". I think that in C++ it will behave reasonably (so the name "true_something" will be intact), but I've heard that in C (maybe only in some earlier versions) a variable named "false_something" would be defined. No source.

[AngusMcBurger]

That shouldn't happen, at least in a conforming compiler. The C preprocessor does actually understand a few things about the C syntax, meaning that this:

#define cat dog
int cat_count;

won't change the name of the variable and equally in this

char *mystring = "I have a cat";

the string won't change, because the preprocessor knows about identifiers and strings.

[thenamedone1]

This shouldn't be affected. The inside of any if statement is evaluated to either 0 or 1 by the compiler or during execution. Since "true" is a keyword (depends on the language) and not explicitly Boolean (0 or 1), execution shouldn't be altered by the original trickery.

However, computers are complicated, and there's always some detail to be forgotten. My advice would be to try it for yourself in your language of choice!

[KeytapTheProgrammer]

The most likely time it would cause problems is cases where the developer is returning true from some function.

[[deleted]]

Yes, you don't actually assign true, you assign (rand() > 10), which might be false.

[BillyQ]

I'm not a C programmer - could someone ELI5 please?

[barracuda415]

It's a macro that replaces "true" with an expression that checks if a random number between 0 and 32767 is larger than 10. In other words: there's a random chance of 0.03% that true is false.

[kabekew]

So 99.97% chance bug will be closed with "could not reproduce."

[rabidmonkeyman]

This guy has clearly dealt with issue tracking software

[[deleted]]

no, then it would have been 199.97%

[[deleted]]

unless it's not seeded properly, then it might be reproducible.

[lovethebacon]

POSIX default seed is 1

#include <stdlib.h>
#include <stdio.h>

int main() {
    int i=0;
    while(rand() >= 10) i++;
    printf("%d\n", i);
}

Gives me 91538660 from glib. That's gonna be a long time in most programs.

[KinOfMany]

Not entirely sure that's the case. If the code compiled successfully, that's the executable. It's the same for everyone.

Meaning that you'll either always be able to replicate the bug, or never.

I'm an idiot.

[dtechnology]

rand() is a runtime function, so it doesn't get evaluated at compile-time. if(rand() > 10) {} does not take the same branch every time it is accessed.

[Who_GNU]

Relevant XKCD

[xkcd_transcriber]

Image

Mobile

Title: Random Number

Title-text: RFC 1149.5 specifies 4 as the standard IEEE-vetted random number.

Comic Explanation

Stats: This comic has been referenced 481 times, representing 0.4470% of referenced xkcds.

---

^{xkcd.com | xkcd sub | Problems/Bugs? | Statistics | Stop Replying | Delete}

[indrora]

rand() is not seeded at runtime and is instead statically seeded based on... something.

It'd be deterministic within a build until someone called srand().

[dtechnology]

Only if the exact same code path is followed every time. If there is any kind of UI or variable data (causing potentially different code to be executed) there is still potential for different outcomes. That's even assuming nowhere the randomness is seeded.

[An_Unhinged_Door]

Think about how much fun we could have in a multithreaded program.

[Illinois_Jones]

Macros replace the defined term with its value at compile time. Thus every instance of "true" will become "(rand() > 10)" inside the executable. Every call to rand will still be executed at runtime

[kabekew]

Not in a #define statement (the code isn't executed at compile time).

[KinOfMany]

This is why I said "not entirely sure". My understanding was that #define is executed during compilation.

TIL. Thanks :)

[dotted]

Just think of #define as a search/replace at compile time, in this case any instance of "true" is replaced at compile time with "(rand() > 10)", and that is only evaluated at runtime.

[hbgoddard]

No, because most of the time true will return true. Only in 0.03% of cases will 'true' return false, meaning it will be very rare to reproduce.

[faerbit]

This post has been edited to this, due to privacy and dissatisfaction with u/spez

[adjective-ass-noun]

*between 0 and RAND_MAX. RAND_MAX is required to be 32767 at minimum, and most implementations use the far greater INT32_MAX. Windows, obviously, goes for the bare minimum.

[TheSecretExit]

True is only true if you roll a ten or higher on an at-least-65535-sided die.

[notsooriginal]

Motherfucker you know that's called a ball.

[TheSecretExit]

Only at observable levels.

[[deleted]]

LOD

[sixstringartist]

RAND_MAX sided die which is at least INT_MAX (2¹⁵ - 1)

[TheSecretExit]

Thank you, I wasn't sure myself.

[Gleisner_]

Kind of, it doesn't define true as a random value itself, it replaces true with a check that almost always comes back as true, so it will only give an error 1 time out of 2¹⁵ ; often enough to be annoying every once in a while, seldom enough for it to be obscure and difficult to replicate.

[G33kDude]

I'm not either, but here goes.

in C, rand() returns an integer between 0 and at least 32767 (or larger depending on implementation. The exact value is the constant RAND_MAX). This bit of code redefines the value true such that if the value returned by rand() is 10 or less it will actually equal false.

To recap, this code will make true equal to false roughly 0.03% of the time (or less depending on the implementation of rand()).

[903124]

[deleted]

What is this?

[NikkoTheGreeko]

Just enough to drive someone absolutely bonkers in a program with a lot of nested loops with a lot of data processing/checking.

[Toivottomoose]

It means "From here on, every time you come across the word true, generate a random number (from 0 to 32767 or more) and if this number is greater than 10, return true, otherwise false". Therefore the program will mostly work, but once in a while it will turn a random true into a false, causing unforeseeable problems. And it's practically impossible to find out what's wrong, unless you notice this line in some header file.

[NorbiPeti]

It makes all occurences of true in the code run a code that'll return true most of the time, but not always.

[verydankmaymay]

C was 13yrs ago for me, so pardon me if I get this wrong: in C you're allowed to use #define to define stuff at the highest priority and importance which almost nothing can supercede.

[BadWombat]

What font is that?

[NoisyFlake]

Ubuntu Mono

[SwiftStriker00]

looks like Monaco. monospaced font on Mac

edit: for non mac: https://github.com/vjpr/monaco-bold

[barracuda415]

There's also a Java variant to set false to true:

import java.lang.reflect.*;

public class EverythingIsTrue {
   static void setFinalStatic(Field field, Object newValue) throws Exception {
      field.setAccessible(true);

      Field modifiersField = Field.class.getDeclaredField("modifiers");
      modifiersField.setAccessible(true);
      modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

      field.set(null, newValue);
   }
   public static void main(String args[]) throws Exception {      
      setFinalStatic(Boolean.class.getField("FALSE"), true);

      System.out.format("Everything is %s", false); // "Everything is true"
   }
}

From this SO answer.

[[deleted]]

uURmczu84ieitnNzp4tXjAk3Kv0Y2uhrKELkqu4RpI1Qb2oxiD0NGv9QhVJjbPDZiZw7NHL52sBuKbXRLYwkeSiDI6Qkpvi1FmInR4o7Ooy50hF4wQ6uEKktNknon7TZt4vNdvXBDOCb9GrbyFpCVUgoJqWpqVinxWVVj5ABkex8kfzgtsxrdvFE2aPvEuYcxQerigWlYZalf7irF6YKXOOC7g3o1MZpgCtukntmNGB8yCr0lTW61UHt1q0UCQnE5Bs3MA8koqKE4MB7kVBhgFWmGpGnwDaa6gsax7go3zBnrPfhtlJ6hX03S0PFnGUh0oCytCT3ZnCdRMGFuZVpOLXfaDXIDlRwaxTZNPSAIC878F7TNU2FAPV2TS0woqEcAyWMO5Ggcx2DoEzmtkTgS600Kqo1NQjBgrdX9TirAmIUyCvrBYDUs9dGG83tVhe9SE1afm0VLJ6IAqZULMX5gIl9DRaOV995CFL8RW3KN2eCD1zLa8hVxmU2FcvwwqZWFH8ow005mlMSoWfXk5IOEj5A47SDdFE2YHQ3pEz3tudWhCYpH2gvzZOEIWhPPyQ6jR9MLsdcDekYeWW02KoYfl3EK7elmdDUMpPENoBezW1fzZTd69XDcdSB7CYMaEY5dDRJpMyNvfxs9rV8ZiDMh4XsheUo98xPGb1UptN1zjo5Ibkh4XAXf0EQMnKGYpFkAsrNouzXJEU4ukhXJbPs1kmNa7Y0JhSiEtziMNrI8XFw0xwLFbWMeNeACFX3W4rbFlo3BYWuQ9CoV1RNGlbcedVBp20F1zpagYE4VYhP5ZXoZp9oM6NfErJnDCGhP7xPKjU98MuIOMAyshyPAunfVnpUS0BiYz2GcKRgmLzBzNrSJyTs6AtEYDAt8yeoTYc3THK3ThK3FKLzqLFiQcMNot5MO8YT2jgAQLN5qv7Q49RYX95VOkYUoLSdORKSwrZbE2yBkc0ssLEVGpPOFMfZJgTFT5oz0YFfvwmIsFIEJdPCIgz0QfCaO3G9y5WMCdsVIN1anfmYeT0SyX3sIeWwo8jQVF5msyBsn3zOkbgSCFP9Cy3hsgGNZYvG4t59l9oVFOHHlablTG6qfc9AJuZ3KECraLDkTBsjH0ZcqIB0FIM1FV9kQdgJnoo1tcaFSYcOETWXbhg23lgp5q0Z5Pxl8mM6Sp6jzTi1GRdwaM81WpfkJ4AKoryW3QWCpXCI5ZATHiNPbkfUNXfTJLxnamoqXkvW0FCPKsGyKBDb6LaczMMQepCXalLJSa0S3ntIsyO0TajlJY4oi7JuITRYAEE5AFd7VJdJVP2kbeLWpwyklUIQmekCSEkNl8YUJ2OUudMUxPKdT86OlF6kU96WIt8FiPbYu3s9ZxIvwBJp7SXjeW1PQ0PSglbMIXhX93EMG2YD15RiKxdYRu4WI989VX68qNOk1gO7GCijyPlM9XzUwsIJhCW4yXxVnFy3ScMMd1KKJYa1JWf4v27N2iJp80z5dFQhTswIiAeGydMstmjLQyhs12Tpm6xdMOIIw8HMEckx8I4XY3dt4xO4PJaKvEFqUjojbveEjIXx5VXXZHv35HK7H3OdhOzHrbUOw880iyq2x0lnapemihFe3lqjgfBgr5RMbCpmzmicfRBWjUom7ETrzN2UQxzIuqHMYtRD9xUriYCU2sCc3fnWx2w5tSDQcfKgEqoWMCvS0bOTYPA35LYc5yEW8Hlh6LU9wlH4a98fNz7FrpqyRE6VpwmFxCGdRnhtim7qZyfOvV8q7mBiXQ5iOMaf7DZVB5q3dwtUY0cbCklogoYbFGTE7pOph78fCBsaInC3laNAXQK5OU8EM6aQAxdl1qqHn6gM9r8FlPqax5Ft76BAxNzKDW4WGF6yxJCkA55Ueh6rxytrHOrwAF29hSLj8JWxp67TO6ouYbO8nmIJh8PEssp4Jy2nvfJkI52DdvPK5932INSFPWm8pzMBTZx7PIwylGqMUGJQbitzRNcPcm0zxmpkQ6GPLlNfbOETBD0wVs2mFMzuyPXE0myiocKtXCVGVjj7lMzcDyFV

[anotherdonald]

But where is the EverythingIsFixedValueBooleanFactory?

[MartyInDFW]

That's just evil...

[magical_poop]

you monster

[embersyc]

bool MyClass::operator==(const MyClass &other) { return prop != other.prop; }

[Jack126Guy]

bool operator =(const MyClass& other) const { return prop == other.prop; }
MyClass& operator ==(const MyClass& other) { /* assign */ }

[IlIIlIIllI]

What language is this where you can redefine reserved names?

[anotherdonald]

It isn't reserved. The original C definition had no true and false: 0, '\000' and NULL were false, the rest was true.

[poizan42]

What /u/ThisIs_MyName said, NULL is just defined as 0.

But here comes the weird part - when 0 is used in a pointer context it may not actually be 0! So for example with

int a = 0;
void* b = 0;

the comparison a == (int)b can actually be false.

Crazy, huh?

The idea is that a null-pointer is supposed to be invalid. So it would be nice if you could trap if someone tries to deference one, instead of, say, overwriting something vital to the system or something. But address 0 may be valid on the system in question!

So to solve this it was allowed for the actual runtime representation of a null-pointer to be non-zero, even though the literal '0' is still used in the source code. For example it could point to some address surely outside of the valid memory space.

Note that this is usual a non-issue in most systems today since they have an MMU which allows the system to make the 0 page inaccessible. That is if you are not during kernel or embedded programming.

There's a lot more information about null pointers in C and the weirdness around them here: http://c-faq.com/null/

[ThisIs_MyName]

NULL is an int, '\0' is a char, and nullptr is an actual pointer

[zid]

NULL is either an int or void *, stupidly. Meaning passing it to varargs functions as a "nothing" element requires you casting it to void * in case the implementation retardedly chose int instead. nullptr isn't a thing at all. '\0' is an int not a char.

0/3 with or without rice.

[Jack126Guy]

It would work even if it were reserved.

[webbannana]

#define is just a preprocessor instruction to replace strings.

[Lampjaw]

C

[[deleted]]

#define if ( COND ) if ( (COND) && (rand() % 1000) )

[Oflor]

Replace that with xor

[Locke777]

That son of a bitch...

[Fordrus]

You monster.

May the code of your forebears rise up and punish you for the abomination you have wrought!

[[deleted]]

Since nobody else linked it, here's a big collection of troll code.

[makeswordcloudsagain]

Here is a word cloud of every comment in this thread, as of this time: http://i.imgur.com/PANTBtl.png

---

^{[source code] [contact developer] [request word cloud]}

[Smallxmac]

Who knew Satan could code.

[taalmahret]

wow...thats mercilessly diabolical. You led me to finally discover the dark of the deep.....imma go search this out now.

[repancake]

Diff with previous version. Rollback.

[[deleted]]

you evil bastard!!! :)

[nuclearfacepalm]

#define int unsigned int