CLANG Pass-By-Value Warning?

Question

The following code compiles fine ...

int main (int argc, const char * argv[]) {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    // VARIABLES
    MDD *MDD_structure;
    NSString *mddFile = @"/Users/Gary/Code/Mdd/xTest.mdd";
    NSFileHandle *inFile;
    NSData *inBuffer;
    int MDD_fCount;
    int MDD_vCount;

    // OPEN FILE ON DISK
    inFile = [NSFileHandle fileHandleForReadingAtPath:mddFile];
    if(inFile == nil) NSLog(@"FILE: Open ... ERROR");
    else NSLog(@"FILE: Open ... OK");

    // READ FRAME COUNT
    inBuffer = [inFile readDataOfLength:sizeof(int)];
    [inBuffer getBytes:&MDD_fCount length:sizeof(int)];
    MDD_fCount = CFSwapInt32BigToHost(MDD_fCount);
    NSLog(@"FC: %d", MDD_fCount);

But when I run it through the static analyzer "CLANG LLVM 1.0" I get the following ...

warning: Pass-by-value argument in function call is undefined.
         MDD_fCount = CFSwapInt32BigToHost(MDD_fCount);
                      ^                    ~~~~~~~~~~
1 diagnostic generated.

Can anyone tell me what I am missing?

gary

Answer 1

You're getting an error because clang isn't convinced that simply passing the address of your variable to a function is the same as giving it a value. You could probably initialize MDD_fCount to 0 to start with to get rid of the error.

Answer 2

It means that you haven't initialized MDD_fCount. See this blog post and this other question for additional info.