Error for loop initial declarations are only allowed in c99 or c11 mode

[Error] 'for' loop initial declarations are only allowed in C99 or C11 mode
[Note] use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code

I’m giving the above problem’s solution, note that I’m using DevC++ code editor here

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I’ve just pulled in sum code i wrote a while back and i’m getting the following error:

 error: ‘for’ loop initial declarations are only allowed in C99 mode

 How do I allow «C99 mode»?

 long power (long number, long order)
{
    long result = number;
    for (unsigned int n = 0; n < (order - 1); n++)
    {
        result = result * number;
    }
    if (order == 0)
    {
        result = 1;
    }
    return (result);
}

 Thanks.

post edited by Rowlandski — 2017/06/02 04:35:41

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 03:15:38

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XC16 is a «C89» compiler, with a few C99 extensions.
I don’t think there is a C99 mode in XC16 at all. That’s an awkward way of saying «that is a C99 feature that I don’t support at all».

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 03:15:47

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project properties | compiler options
Cannot recall the exact name of the option but clicking a bit should result in success.

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 04:01:09

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I actually never felt the need for that feature. «localizing variables», yeah, oh well…

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 04:06:57

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du00000001
project properties | compiler options
Cannot recall the exact name of the option but clicking a bit should result in success.

Are you sure? There’s no mention of it in the latest XC16 User Guide.

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 04:15:52

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qhb

du00000001
project properties | compiler options
Cannot recall the exact name of the option but clicking a bit should result in success.

Are you sure? There’s no mention of it in the latest XC16 User Guide.

True, I couldn’t find it either.

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 04:25:55

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Ahem, why did’nt you read the next line the compiler outputs ?  (XC16 v1.31)

 ../main.c:1368:2: error: ‘for’ loop initial declarations are only allowed in C99 mode
../main.c:1368:2: note: use option -std=c99 or -std=gnu99 to compile your code

 Adding this option works as expected.
However this changes more than this, i.e. you then will get different warnings for other stuff etc …

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 04:29:42

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Must be a GCC option that’s not officially supported.

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 04:35:12

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Sorry, missed the info.

 using:

 -std=gnu99

 Works

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 06:20:55

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Careful when setting, «additional options», due to mplab x bugs these can get deleted.

 It has happened to me a lot.  You have to paste them back in, annoying when you have 10 projects open.

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 08:21:03

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rowlandwhiffin
-std=gnu99

 Be aware that this causes the language the compiler supports to be «GNU C 99», which is different from ISO Standard C 99.

Mark (this opinion available for hire)

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/02 08:39:04

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You’re prone to die — one or another way.

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2017/06/04 05:10:27

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Hi, I use Matlab/Simulink(R) coder for code generation for dsPIC, PIC18 and ARM Cortex M4 (using Keil).
I always put the additional option: -std=gnu99, and the code work excellent. 
With this set, implement PIDs, Transfer functions, State flow, Fuzzy Logic, Kalman filter, etc. etc. is too easy.
With this additional option, you can use: for (uint8_t i = 0; i<10; i++), for example.

 Although it is not stated in the literature of Microchip, it is always good to work with the gnu99 standard since you have access to shared libraries, for example using Matlab / Simulink coder, one gets to have the power of simulink inside the dsPIC. And for example in ARM, it is possible to use the CMSIS libraries in the generated code. GNU99 also allows programming using the MISRA-C 2012 guidelines for critical systems.

 I recommend using the new standards for numerical formats, uint8_t instead of unsigned char, int16_t instead of int, etc.

#include <stdint.h> /* Includes uint16_t definition */
#include <stdbool.h> /* Includes true/false definition */

 Regards!

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2022/03/11 12:03:22

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Project Properties > Conf > XC16 > XC16 (Global Options) > Additional Options «-std=gnu99»

I wish I’d paid attention in my high school typing class…

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Re: error: ‘for’ loop initial declarations are only allowed in C99 mode


2022/03/11 13:34:54

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5 years on, I rather think the OP has moved on.

Hi friends,

I am using GNU GCC Compiler

OS: win7 32bit

/* Program 4.2 Drawing a box */
#include <stdio.h>
int main(void)
{
printf(«n**************»); /* Draw the top of the box */
for(int count = 1 ; count <= 8 ; ++count)
printf(«n* *»); /* Draw the sides of the box */
printf(«n**************n»); /* Draw the bottom of the box */
return 0;

}

when i try to compile the code i got fallowing error.

C48.c|6|error: ‘for’ loop initial declarations are only allowed in C99 mode|
C48.c|6|note: use option -std=c99 or -std=gnu99 to compile your code|

If anybody know how to change it to c99mode please help me.

Thanks & Regards,

Deva

Hi, I changed to -std=c99 mode is this way correct ?

Please see picture
Untitled.png:

Hi friends,

My problem solved. many of them adviced me to change settings to -std=c99 But its not worked because my compiler is GNU GCC Compiler.

Here is see how the problem is fixed.

In the Compiler and Debugger settings. Compiler settings tab — Other Options. I added there -std=gnu99

So Problem solved.

Friends thanks very much for your advices & time.

Thanks & Regards,

Deva

« Last Edit: November 10, 2011, 04:24:57 pm by deva »

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zabzonk

Go to the Project menu, then Build Options…, then Compiler Settings|Other options tab, then enter -std=c99 and hit OK.

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Hi,

Thanks for your reply. In the projecet menu build options is disable I mean its not highlited. How can we enable it?.

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zabzonk

CB is project based. Before you write any code, create a project from Create New Project on the CB startup screen, and select Console Application — the Build Options will be enabled after you create a project.

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CB is project based. Before you write any code, create a project from Create New Project on the CB startup screen, and select Console Application — the Build Options will be enabled after you create a project.

Wrong, C::B supports single file compilation, too.
For the compilation it uses the default compiler,
so you can set the option in the settings,
but this is not a good practice in the long run.
No, debugging is supported in single file mode.

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(most of the time I ignore long posts)
[strangers don’t send me private messages, I’ll ignore them; post a topic in the forum, but first read the rules!]

zabzonk

> Wrong, C::B supports single file compilation, too.

What is «wrong»? Do you deny that that CB is project based? Can you use Build Options without a project, which is what the OP needs to do, without using what you yourself say is «bad practice»? No, you can’t.

« Last Edit: November 10, 2011, 10:34:52 am by Neil Butterworth »

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I gues you use a *.c file.
The easiest way would be to rename it to *.cpp, so it is compiled with the c++-compiler.

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zabzonk

> The easiest way would be to rename it to *.cpp, so it is compiled with the c++-compiler.

But then he runs into problems if he uses C99 features not supported by C++.

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IMO, Jens is correct. You problem consists in «for( int count = 1 ; …» This kind of declaring local variables in a loop statement (or other statements) is usual in C++ for a long time. Perhaps, a norm is it starting from C99. GCC is over strict sometimes …

(1) Either switch to C++ by renaming 48.c to 48.cpp or selecting C++ compiler explicitely.
(2) Or declare «int count» like a normal variable declaration at the beginning of main().

When you opt for (1) you can get a similar paranoid message. When you opt for (2), you should pass even with a  C compiler.

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zabzonk

@Radek. It is perfectly legal (and good)  C99  code, and the OP obviously wants to use C99. Telling him to switch to C++, a completely different language, is IMHO very bad advice.

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Hi friends,

Non of the your advices working. Is there any way still fix the problem. Actually I am newbie to programming. I am just teaching my self from book «C-FromNoviceToProfessional4thEd(2006)» by Ivor Horton,  Apress. 

I tried to compile the same code in Borland Turboo C++ compiler. Its work fine.

But i really like to use CB because its highlight the syntax in colors. So, code looks clean & good.

Any help greately appreciated.

Thanks & Regards,

Deva

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zabzonk

@Deva The code will definitely compile if you rename the file to a  .cpp extension, but if you are trying to learn C rather than C++ this is not the best solution, as it means things that are mistakes in C but not in C++ will not be caught. My solution of creating a console application project and supplying the -std=c99 option should definitely work — it did when I tried it myself — and is the correct way to go if you want to learn C99. Did you actually try it?

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The following does not work?

#include <stdio.h>
int main(void)
{
  int count;
  printf("n**************");        
  for( count = 1 ; count <= 8 ; ++count ) printf("n* *");
  printf("n**************n");
  return 0;
}

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