Re: [PATCH 5/7] vcs-svn: fix cppcheck warning

From: Jonathan Nieder <jrnieder@gmail.com>
Date: May 24, 2012, 14:20 UTC
Message-ID: <20120524142058.GA3732@burratino>
In-Reply-To: <1337868259-45626-6-git-send-email-davidbarr@google.com>

Hi,

First, thanks much for this series!  I especially like patch #4.

David Barr wrote:

> [vcs-svn/fast_export.c:211]: (warning) Using sizeof with a numeric constant
> as function argument might not be what you intended.

[...]

> -		assert(!signed_add_overflows(preimage.max_off, 1));
> +		assert(!signed_add_overflows(preimage.max_off, (off_t) 1));

I think this is due to a typo in the compat-util.h compatibility layer you are using. In git.git there is

	#define signed_add_overflows(a, b) \
	    ((b) > maximum_signed_value_of_type(a) - (a))

so the sizeof() operator is applied to preimage.max_off and all is well. By contrast, in svn-dump-fast-export.git it says

	#define signed_add_overflows(a, b) \
		((a) > maximum_signed_value_of_type(b) - (b))

Though the comment describing signed_add_overflows() does say that "a" and "b" should have the same type, I like being able to ask if signed_add_overflows(n, 1) in a non-fussy way that does not introduce subtle bugs when the type of "n" changes, so I'd prefer not to take this patch.

Hope that helps, Jonathan