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Home » Developing U++ » U++ Developers corner » AString::Compare missing explicit return value (q will = 0 if the loop isn't broken. This value should be returned explicitly.)

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AString::Compare missing explicit return value [message #44081]

Tue, 23 December 2014 10:56

rainbowsally
Messages: 29
Registered: December 2014

Promising Member

For x86-based C/C++, the eax/rax register is usually returned by default (for int types) and this is probably the register holding 'q' below, but it can't be counted on.

File: uppsrc/Core/AString.hpp

template <class B>
int AString<B>::Compare(const tchar *b) const
{
	const tchar *a = B::Begin();
	const tchar *ae = End();
	for(;;) {
		if(a >= ae)
			return *b == 0 ? 0 : -1;
		if(*b == 0)
			return 1;
		int q = cmpval__(*a++) - cmpval__(*b++);
		if(q)
			return q;
	}
	// -rs added 1 line to explicitly return q(=0)
	return 0;
}

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Re: AString::Compare missing explicit return value [message #44085 is a reply to message #44081]

Tue, 23 December 2014 14:53

dolik.rce
Messages: 1793
Registered: August 2008
Location: Czech Republic

Ultimate Contributor

Hi rainbowsally,

There was nothing wrong with the function. If you look carefully, you'll find out that the line you added will actually never be called Wink

There is no way the code evaluation could get out of the infinite for-loop, other than one of the first three return statements.

So even though some compilers might warn about missing return statement, there is actually no problem or undefined behavior in this function.

Best regards,
Honza

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Re: AString::Compare missing explicit return value [message #44088 is a reply to message #44085]

Wed, 24 December 2014 04:42

rainbowsally
Messages: 29
Registered: December 2014

Promising Member

Hi Honza.

Yer right. Thanks. Smile

I'll un-fix my version.

dolik.rce wrote on Tue, 23 December 2014 14:53

Hi rainbowsally,

There was nothing wrong with the function. If you look carefully, you'll find out that the line you added will actually never be called There is no way the code evaluation could get out of the infinite for-loop, other than one of the first three return statements.

So even though some compilers might warn about missing return statement, there is actually no problem or undefined behavior in this function.

Best regards,
Honza

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