Given the source code listed at the end of this message, and a tags file
generated from that source, I will demonstrate that a bug in the operation
of the :tag command has been introduced after Vim 6.3, and persists today.
When navigating the tag stack with the :tag and :pop commands, Vim is
supposed to remember which one of many matching tags I previously
selected, so that as I climb and descend the tag stack, I return to the
same location I originally jumped to.
The helpfile states that the tag match number won't change when using :pop
or :tag. (tagsrch.txt for Vim version 7.1, line 130)
However, I find that when I use the :tag command without arguments to
climb the tag stack, the cursor jumps to the first tag entry in the match
list instead of the one I selected. The tag stack is updated so that the
current entry points to the first matching tag instead of the one I chose.
The relevant documentation is located at
:help :pop
:help :tag
:help :tags
I have reproduced this bug in several Vim versions ranging from 7.0 to a
fully-patched 7.2, on both Windows XP and Linux.
Steps to reproduce:
1. Generate a tags file from the source code below.
2. Open the file with `vim -u NONE main.c`
3. Position the cursor on the call to func1() in main() on line 32.
Press 'g Ctrl-]' and choose to jump to the definition of func1() that
takes an integer argument. From there, jump to the definition of
func2() that also takes an integer. Finally, jump into the definition
of func3().
At this point, the output of :tags should look like this:
# TO tag FROM line in file/text
1 2 func1 32 func1(i);
2 2 func2 5 func2(i);
3 1 func3 15 func3(i);
>
4. :3pop your way back to the bottom of the tag stack.
At this point, the output of :tags should look like this:
# TO tag FROM line in file/text
> 1 2 func1 32 func1(i);
2 2 func2 5 func2(i);
3 1 func3 15 func3(i);
Notice that the tag number from the match list (the number beneath the
heading "TO") hasn't changed.
5. If you are following these steps in Vim version <= 6.3, the :tag command
will return you to the same definition of func1() that you had
selected earlier, that is, your cursor will jump to the definition of
func1(int i).
If you are following along in a version of Vim > 6.3, the :tag command
will instead jump the cursor to the first definition of func1() found
in the tags file, func1(double d).
In Vim > 6.3, the output of :tags now looks like this:
# TO tag FROM line in file/text
1 1 func1 32 func1(i);
> 2 2 func2 5 func2(i);
3 1 func3 15 func3(i);
As I have stated before, this is incorrect because the :tag command
should not modify the match number, and should return the cursor to
the definition of func1(int)
/* main.c */
/* vim:set nofoldenable filetype=c: */
void func1(int i) /* i want to come here FIRST */
{
func2(i);
}
void func1(double d)
{
func2(d);
}
void func2(int i) /* i want to come here SECOND */
{
func3(i);
}
void func2(double d)
{
int i;
func3(i);
}
void func3(int i)
{
i++;
}
int main(void)
{
int i;
func1(i);
}
/* EOF */
--
Erik Falor
Registered Linux User #445632 http://counter.li.org
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