Wireshark · Wireshark-dev: Re: [Wireshark-dev] error: logical && with non-zero constant will always evaluate as true

[Guy Harris <guy@xxxxxxxxxxxx>]

On Jan 3, 2013, at 1:40 PM, Jeff Morriss <jeff.morriss.ws@xxxxxxxxx> wrote:

> Jeff Morriss wrote:
>> My (Fedora 10) gcc 4.3.2 was also generating this warning; it would seem that a fair spread of gcc versions seem to have the problem.
>> I added a configure check to stop using -Wlogical-op if the compiler is generating this warning in r46916.
> 
> Interestingly the Ubuntu buildbot says it would also get the warning:
> 
>> checking whether we can add -Wlogical-op to CFLAGS... yes
>> checking whether -Wlogical-op generates warnings from strchr()... yes

Which means that

	#include <string.h>
          
	int
	foo(char *sep, int c)
	{
	        if (strchr (sep, c) != NULL)
        	        return 1;
	        else
        	        return 0;
	}

	int
	main(int argc, char **argv)
	{
	        return foo(\"<\", 'a');
	}

fails to compile with the CFLAGS value at the time the test is done, plus -Werror; it could be failing for some other reason.  To quote the comment when I finally got it working for -Wshadow:

	Declare foo() before defining it - if we configure with
	--enable-extra-gcc-checks, given that we're building with -Werror (so
	that we find out whether the compiler issues a warning for a particular
	construct), we have to avoid constructs that will provoke *other*
	warnings.

so the code in question has to avoid whatever other warnings are being used, and the Ubuntu buildbot builds with --enable-extra-gcc-checks, so it warns about functions not declared with prototypes before they're defined.  I've checked in a change to declare foo() before it's defined; we'll see whether that fixes it.