Jeremiah Mahler <jmmahler@xxxxxxxxx> writes:
> On Sat, May 17, 2014 at 06:00:14AM -0400, Jeff King wrote:
>>
>> If you wanted to know whether it was set, I guess you'd have to compare
>> it to the default, like:
>>
>> if (signature_file) {
>> if (signature && signature != git_version_string)
>> die("you cannot specify both a signature and a signature-file");
>> ... read signature file ...
>> }
>>
>
> That works until someone changes the default value.
> But if they did that then some tests should fail.
>
> I like the address comparision which avoids a string comparision.
Well, "avoids" is not quite a correct phrasing, because !strcmp()
would be wrong there. You cannot tell "the user did not set
anything and the variable stayed as the default" and "the user
explicitly gave us a string but it happened to be the same as the
default" apart with !strcmp(). Address comparison is not just
"avoids" but is the right thing to do in this case.
>> though it's a bit ugly that this code has to know what the default is.
Avoiding that is easy with an indirection, no? Something like this
at the top:
static const char *the_default_signature = git_version_string;
static const char *signature = the_default_signature;
and comparing to see if signature points at the same address as
the_default_signature would give you what you want, I think.
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