Convert Integer to Hex in an array of chars

Hey there,

I want to know if there is a routine that can take in an array of char, and an integer, convert the integer to hex and store the hex representation as text in the char array.

For example, if integer is 123, its hex representation is 0x7B, so it can return 7 and B in the char array.

Any routine/code/function would be helpful.

Thanks

Code:

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int main( void )
{
        const int len = 1024;
        char buf[ len + 1 ];
        int val = 123;
        sprintf( buf, "%x", val ); // or if avaliable: snprintf( buf, len, "%x", val );
        puts( buf );
        return 0;
}

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Quote:

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const int len = 1024;
char buf[ len + 1 ];

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Every time I try initializing an array with a const in Visual Studio , I get an error saying
Expected constant expression.
Cannot allocate array of size 0.
This only happens in C and not C++. Although, it works if I use a macro -

Code:

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#define LEN 1024
char buf[ LEN  + 1 ];

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Does anyone know why that is ? I thought the const keyword was added to the C standard.

C recognizes the const keyword, but regardless if the value used to create the array is const or not, in C it is still considered a variable length array. In other words you can only do that if you are using C99; it is illegal in C90.

Ah, I see. So Visual Studio supports C90 then.

Quote:

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Originally Posted by Spidey

Ah, I see. So Visual Studio supports C90 then.

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Most compilers still only support C90. Even though C99 is almost a decade old, there are very few compilers which are fully C99 compliant.

I did try writing a quick code to check this scenario on Dev-C++. It turned out to be compiling with no warning. Which I guess I’m running C90 complaint compiler. But surely there should be somewhere in the IDE where I can find this information. Any ideas where?

~ssharish

Many popular compilers can have C99 compliance explicitly turned on, actually. Usually the website of the developers of your compiler can field questions about compliance.

Ah, I see. I never noticed that. I found one called lcc, I guess I'll try it out now :D

>> I did try writing a quick code to check this scenario on Dev-C++. It turned out to be compiling with no warning. Which I guess I’m running C90 complaint compiler. But surely there should be somewhere in the IDE where I can find this information. Any ideas where?

Not really. The IDE is just a front end for whatever compiler you set it up to use, and as such it doesn't know the particulars of the compiler (VS is probably an exception, but then there isn't such a clear distinction between compiler and IDE there).

Yeah, usually a compiler won't warn about the parts of C99 that it supports. For instance, it will compile fine in GCC if you do:

Code:

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gcc -Wall file.c

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But it will warn you if you do:

Code:

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gcc -Wall -pedantic file.c

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I have used lcc for embedded projects. I would highly recommend against using it for something you don't absolutely have to use it on. It is not the best compiler in the world.

Quote:

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I have used lcc for embedded projects. I would highly recommend against using it for something you don't absolutely have to use it on. It is not the best compiler in the world.

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Yeah, I'm fine with Visual Studio. Just trying out some C99!