C Program Won't Compile in Visual Studio 2010

Question

I have a simple C program that I can compile via command line on Linux easily enough but want to use Visual Studio to debug the program so that I can more easily see what it's doing but I cannot get it to compile.

I have created a new cpp Win32 console application. Added my .c and .h file but I cannot get it to compile. I get 100+ errors that primarily seem to be red herrings. For instance I have an error saying a variable isn't declared when I can see it declared on the line immediately before. For instance:

int i;
for (i = 0; i < unpacked_length; i++)
{

on the "for" line I get an error: "error C2065: 'i' : undeclared identifier"

So something else is obviously going on. One error that seems legit is this one:

static unsigned char* Base64_Charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

IntelliSense: a value of type "const char *" cannot be used to initialize an entity of type "unsigned char *"

Since this works when compiling via command line I don't know why the intellisense would be giving this error here unless this compiler has different rules than the other one I used via command line. I haven't done any C for about 15 years and don't know if this could be a difference in compiler or if there is something else going on here.

The only includes in the source are:

#include "dtcrypt.h"
#include <string.h>
#include <stdlib.h>

Appreciate any help!

Can you edit your post to include the smallest complete code that exhibits the problem? — Oliver Charlesworth
– Oliver Charlesworth, Commented Jul 6, 2012 at 19:33
I will see what I can do. This code is an encryption program that a 3rd party has written for us so I can't post the program. I will reduce it to a size that repro's the problem if indeed the answer doesn't pop to someone by seeing the details of my situation above. — omatase
– omatase, Commented Jul 6, 2012 at 19:34

Adam Rosenfield · Accepted Answer · 2012-07-06 19:35:04Z

3

Visual Studio 2010 only supports ANSI C (aka C89), it does not support the more modern C99 or C11 language standards. ANSI C requires you to declare all of your variables at the top of a function, you cannot define them in the middle of a function just before they are used. So try rewriting your code like this:

void my_function()
{
    /* Variable declarations go here */
    int i;
    ...

    /* Now teh codez */
    for (i = 0; i < unpacked_length; i++)
    {
        ...
    }
}

For the second error, Intellisense complaining that it can't convert a pointer to const char to a pointer to const unsigned char. String literals have type char[] (array of characters), and char is signed by default. So, you should declare your variable as type const char * instead of const unsigned char *. Or, you can ignore it, since it's not a compiler error, but it is a warning at certain warning levels.

answered Jul 6, 2012 at 19:35

Adam Rosenfield

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1 Comment

omatase Over a year ago

I would have never figured this out. Thanks so much!

Seva Alekseyev · Accepted Answer · 2012-07-06 19:33:22Z

1

Whether char is signed or not is a compiler setting in Visual C++. Change it to unsigned to match the expected GCC environment. Project properties, C/C++, Language.

As for i in the loop, there must be some extra info that you're not showing. The two pasted lines look kosher to me.

That said, I have ample experience porting code between VC++ and GCC - it's hardly ever pretty.

answered Jul 6, 2012 at 19:33

Seva Alekseyev

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1 Comment

user1342784 Over a year ago

You can also just remove the 'unsigned' from the line. If the compiler defaults 'char*' to 'unsigned', it's redundant, otherwise it's wrong.

vikramjitSingh · Accepted Answer · 2012-07-07 17:21:16Z

0

Instead of messing up with compiler settings typecast it to "unsigned char *"

E.g. : unsigned char* Base64_Charset = (unsigned char *)"ABCDEFG";

answered Jul 7, 2012 at 17:21

vikramjitSingh

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