[aur-dev] [PATCH] Fix: FS#13189, infinite variable replacement cycle

[Gergely Imreh]

Hi,

 Bug report FS#13189 brought to light a situation when certain lines
in the PKGBUILD would cause the pkgbuild.php end up in an infinite
cycle.
 Example is a line such as:
 foo=$foo
 or as in the bug report:
 CXXFLAGS=$CXXFLAGS' -fpic'

 In the first case, e.g. $foo would be recognized as a call for
replacement for "foo", and then replaced with "$foo", then checked
again for values to replace.... you can guess how well it goes...

 This patch removes this situation by setting the variable value to
empty (to ""), if it recognizes that there would be such a cycle. This
behaviour is not exactly what bash would do, since e.g. if there are
two lines in the PKGBUILD such as:
 foo=something
 foo=$foo
 then in bash in the end foo would have a proper value ("something"),
while in our case it would be empty. In my opinion this is not a
problem, since generally these kind of PKGBUILDs could be considered
malformed.....

 The eval type parameter substitution is not changed at the moment,
since even if does not give the same value as bash, it does not cause
such cycle as the normal substitution.

 Cheers,
        Greg