Error assignment to cast is illegal lvalue casts are not supported - Исправление ошибок и поиск оптимальных решений проблем

After a clean checkout of the latest code I ran the following on my Macbook with OSX High Sierra:

GCMDiskHeader.c:191:18: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->unknown1 = *((u32*)rawHeader)++;
                       ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:199:28: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->debugMonitorOffset = *((u32*)rawHeader)++;
                                 ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:202:29: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->debugMonitorAddress = *((u32*)rawHeader)++;
                                  ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:207:19: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->dolOffset    = *((u32*)rawHeader)++;
                           ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:210:19: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->fstOffset    = *((u32*)rawHeader)++;
                           ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:213:18: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->fstSize              = *((u32*)rawHeader)++;
                                   ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:216:22: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->fstSizeMax   = *((u32*)rawHeader)++;
                           ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:219:22: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->userPosition = *((u32*)rawHeader)++;
                           ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:222:22: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->userLength   = *((u32*)rawHeader)++;
                           ~^~~~~~~~~~~~~~~~~~
GCMDiskHeader.c:225:19: error: assignment to cast is illegal, lvalue casts are
      not supported
        h->unknown2             = *((u32*)rawHeader)++;
                                   ~^~~~~~~~~~~~~~~~~~

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Looks like no one’s replied in a while. To start the conversation again, simply

ask a new question.

hi…….Every one….

1…..i have another problem with JSON Parsing

2…i read .json file , store in Dictionary ,Array & then pirnt on Console.

3….. Now i try to print this text on Label by using…..

(UILabel*)[self.view viewWithTag:1].text = [firstEmployee valueForKey:@»EmployeeName»];

….at this time raises 1 error like……..

Error: Property ‘text’ not found on object of type ‘UIView *’.

Please help me

iPhone 5,

Mac OS X (10.7.5),

XCode 4.6

Posted on Mar 29, 2013 5:11 AM

I put the opening parenthesis in the wrong place. If you want to use one line, parentheses should be as follows. Two lines per xnax post is easier to debug.

((UILabel*)[self.view viewWithTag:1]).text = [firstEmployee valueForKey:@»EmployeeName»];

Error #2 is a separate problem, it seems like your device is not provisioned for development.

Posted on Mar 30, 2013 10:41 AM

problem With typecasting at JSONParsing?

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Я пытаюсь реализовать оператор mod на двойное число, которое временно преобразуется в целое число (округлено), но компилятор (clang), похоже, не так и возвращает ошибку: assignment to cast is illegal, lvalue casts are not supported,
Например, в этом фрагменте

double a;
int b;
(int)a %= b;

Есть ли способ обойти это ограничение?

Решение

То, что вы делаете, незаконно. поговорка (int)a = ... незаконно, потому что вы не можете разыграть a в целое число таким образом. Вы должны разыграть его справа от задания.

Если вы действительно хотите сделать это, вы можете сказать:

double a;
int b;
a = (double)((int)a % b); /* Casting to a double at this point is useless, but because a is a double-type, the result of the modulus it will be implicitly casted to a double if you leave out the explicit cast. */

Я бы посоветовал присваивать результат модуля новой переменной int, но это ваш выбор.

редактироватьВот пример этого: http://ideone.com/tidngT

Кроме того, стоит отметить, что приведение двойного числа к целому не округляет его, а просто усекает его. И, если значение вашего двойника выше, чем диапазон intтогда это может привести к неопределенному поведению.

Другие решения

Других решений пока нет …

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Description

Nickolay V. Shmyrev

2007-05-21 15:29:40 UTC

The following program doesn't compile due to invalid lvalue in increment. The most strange thing is that gcc somehow ignores type coercion

int main ()
{
int **a;
void **b;

*b++;            /* works fine */
*((void **)a)++; / gives error */

return 0;
}

Comment 1

Andreas Schwab

2007-05-21 15:45:19 UTC

A cast is not an lvalue.

Comment 2

Nickolay V. Shmyrev

2007-05-22 18:16:37 UTC

Ok, I understand it. Gcc dropped support for cast in lvalues. But can the message be more specific about the problem itself. It's really hard to understand the reason from the current one.

Comment 3

Andrew Pinski

2007-05-22 18:27:16 UTC

t.c:9: error: lvalue required as increment operand


I don't see what the problem is, the error message is clear, a lvalue is required for the increment operand.

Comment 4

Nickolay V. Shmyrev

2007-05-22 18:33:38 UTC

gcc can explain why ((void **)a) is not lvalue, it's really not that clear.

Comment 5

Andreas Schwab

2007-05-22 21:32:56 UTC

Because the standard says so?

Comment 6

Nickolay V. Shmyrev

2007-05-22 21:36:01 UTC

Ok, add a line:

"According to standard cast is not lvalue"

I'll be happy.

Comment 7

Andreas Schwab

2007-05-22 21:51:01 UTC

Everything is "according to the standard".  That's where C is defined.

Comment 8

Nickolay V. Shmyrev

2007-05-23 00:12:52 UTC

The point I'm trying to express is that it's useful for user to have more precise explanation.

gcc dropped a lot of features which weren't included in standard recently and thus many of us wondering why the code which compiled before doesn't compile now. It's fine for me to have strict compiler but it's also useful to get at least an idea what compiler doesn't like without reading whole standard.

Comment 9

Andrew Pinski

2007-05-23 00:27:25 UTC

(In reply to comment #8)
> gcc dropped a lot of features which weren't included in standard recently and
> thus many of us wondering why the code which compiled before doesn't compile
> now. It's fine for me to have strict compiler but it's also useful to get at
> least an idea what compiler doesn't like without reading whole standard.

And that is exactly why GCC has changes page to describe these changes.  Yes this specific change is documented on that page.

Comment 10

Manuel López-Ibáñez

2007-05-23 16:57:17 UTC

(In reply to comment #8)
> The point I'm trying to express is that it's useful for user to have more
> precise explanation.
> 

Would you be happy with something like?

t.c:9: error: lvalue required as increment operand
t.c:9: note: a cast is not a lvalue

Perhaps we could even pack it in a single line.

The feasibility of this depends on whether we can get this information when we emit the diagnostic. I think if someone wants to pursue it, it shouldn't be difficult. So why not keep it open? Low-hanging fruit like this is ideal for newbies.

Comment 11

Nickolay V. Shmyrev

2007-05-23 17:06:13 UTC

Exactly :) Thanks Manuel

Comment 12

Andrew Pinski

2021-09-28 08:51:12 UTC

Clang gives a decent error message:

<source>:7:3: error: assignment to cast is illegal, lvalue casts are not supported
*((void **)a)++; /* gives error */
 ~^~~~~~~~~~~~~

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