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Re: CLang wrong analysis?
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Re: CLang wrong analysis?


  • Subject: Re: CLang wrong analysis?
  • From: Roland King <email@hidden>
  • Date: Mon, 28 Mar 2011 22:41:57 +0800

Not that I can see. I'd file that exact test case as a bug. clang is not yet perfect, it's a bit new to be perfect. I've filed a couple of bugs against it so far. It's pretty damned good however. 


On 28-Mar-2011, at 10:36 PM, Jean-Denis Muys wrote:

From XCode 4.01 analyze, this line:

        for (j = i; j < (i + 3); j++) {

reports: "The left operand to '+' is always 0".

I am scratching my head as I don't think that is correct. Here is the full routine:


+ (NSString*)base64forData:(NSData*)theData {

const uint8_t* input = (const uint8_t*)[theData bytes];
NSInteger length = [theData length];

    static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    NSMutableData* data = "" style="color: #7235a9">NSMutableData dataWithLength:((length + 2) / 3) * 4];
    uint8_t* output = (uint8_t*)data.mutableBytes;

NSInteger i;
    for (i=0; i < length; i += 3) {
        NSInteger value = 0;
NSInteger j;
        for (j = i; j < (i + 3); j++) { // <------------- The left operand to '+' is always 0
            value <<= 8;

            if (j < length) {
                value |= (0xFF & input[j]);
            }
        }

        NSInteger theIndex = (i / 3) * 4;
        output[theIndex + 0] =                    table[(value >> 18) & 0x3F];
        output[theIndex + 1] =                    table[(value >> 12) & 0x3F];
        output[theIndex + 2] = (i + 1) < length ? table[(value >> 6)  & 0x3F] : '=';
        output[theIndex + 3] = (i + 2) < length ? table[(value >> 0)  & 0x3F] : '=';
    }

    return [[[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding] autorelease];
}


Am I missing something?

Jean-Denis

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References: 
 >CLang wrong analysis? (From: Jean-Denis Muys <email@hidden>)

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