On Wed, Mar 05, 2014 at 08:58:26AM +0100, Johannes Sixt wrote:
> Here is a patch that I'm carrying around since... a while.
> What do you think?
>
> The pattern I chose also catches variable definition, not just
> functions. That is what I need, but it hurts grep --function-context
> That's the reason I didn't forward the patch, yet.
If by variable definition you mean:
struct foo bar = {
- old
+ new
};
I'd think that would be covered by the existing "struct|class|enum".
Though I think we'd want to also allow keywords in front of it, like
"static". I suspect the original was more meant to find:
struct foo {
-old
+new
};
> The parts of the pattern have the following flaws:
>
> - The first part matches an identifier followed immediately by a colon and
> arbitrary text and is intended to reject goto labels and C++ access
> specifiers (public, private, protected). But this pattern also rejects
> C++ constructs, which look like this:
>
> MyClass::MyClass()
> MyClass::~MyClass()
> MyClass::Item MyClass::Find(...
Makes sense. I noticed your fix is to look for end-of-line or comments
afterwards. Would it be simpler to just check for a non-colon, like:
!^[ \t]*[A-Za-z_][A-Za-z_0-9]*:($|[^:])
> - The second part matches an identifier followed by a list of qualified
> names (i.e. identifiers separated by the C++ scope operator '::')
> [...]
A tried to keep the "looks like a function definition" bit in mine, and
yours loosens this quite a bit more. I think that may be OK. That is, I
do not think there is any reason for somebody to do:
void foo() {
call_to_bar();
-old
+new
}
That is, nobody would put a function _call_ without indentation. If
something has alphanumerics at the left-most column, then it is probably
interesting no matter what.
> - The third part of the pattern finally matches compound definitions. But
> it forgets about unions and namespaces, and also skips single-line
> definitions
>
> struct random_iterator_tag {};
>
> because no semicolon can occur on the line.
I don't see how that is an interesting line. The point is to find a
block that is surrounding the changes, but that is not surrounding
the lines below.
> Notice that all interesting anchor points begin with an identifier or
> keyword. But since there is a large variety of syntactical constructs after
> the first "word", the simplest is to require only this word and accept
> everything else. Therefore, this boils down to a line that begins with a
> letter or underscore (optionally preceded by the C++ scope operator '::'
> to accept functions returning a type anchored at the global namespace).
> Replace the second and third part by a single pattern that picks such a
> line.
Yeah, this bit makes sense to me.
Both yours and mine will find the first line here in things like:
void foo(void);
-void bar(void);
+void bar(int arg);
but I think that is OK. There _isn't_ any interesting surrounding
context here. The current code will sometimes come up with an empty
funcline (which is good), but it may just as easily come up with a
totally bogus funcline in a case like:
void unrelated(void)
{
}
void foo(void);
-void bar(void);
+void bar(int arg);
So trying to be very restrictive and say "that doesn't look like a
function" does not really buy us anything (and it creates tons of false
negatives, as you documented, because C++ syntax has all kinds of crazy
stuff).
_If_ the backwards search learned to terminate (e.g., seeing the "^}"
line and saying "well, we can't be inside a function"), then such
negative lines might be useful for coming up with an empty funcname
rather than the bogus "void foo(void);". But we do not do that
currently, and I do not think it is that useful (the funcname above is
arguably just as or more useful than an empty one).
-Peff
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