Boxing a primitive using the constructor ("new Integer(4)") always
creates a distinct new boxed instance. That's rarely what you need,
and in fact all of those constructors have been deprecated in Java 9.
Using the static "valueOf" method instead ("Integer.valueOf(4)") can
give better performance by reusing existing instances. You no longer
get a unique boxed object, but generally that's OK.
Avoid allocating memory using strdup() and then releasing it using
operator delete. strdup()-allocated memory should be released using
free(), not delete. But in these specific cases, there really was
never any good reason to duplicate the C-style strings in the first
place. Instead, we can safely pass those NUL-terminated char pointers
directly in calls to JNI's NewStringUTF(). NewStringUTF() does not
take ownership of its argument, but rather clones that string data
internally before returning. So using strdup() and delete was just
unnecessary memory churn.
In cases where we need to format, concatenate, or construct new
strings, don't use sprintf() into variable-sized, stack-allocated
arrays. Variable-sized arrays are not portable, and in particular are
rejected by Microsoft's Visual Studio 2017 C++ compiler. Instead, do
our string formatting and manipulations using std::ostringstream
and/or std::string. We just need to be a bit careful about the
lifetimes and ownership responsibilities of allocated data. In
brief, (1) ostringstream::str() returns a temporary string instance
that expires at the end of the enclosing statement, independent of the
lifetime of the ostringstream instance; while (2) string::c_str()
returns an pointer to internal data that remains valid as long as the
string on which it was called is valid and unmodified.
Avoid allocating memory using strdup() and then releasing it using
operator delete. strdup()-allocated memory should be released using
free(), not delete. But in these specific cases, there really was
never any good reason to duplicate the C-style strings in the first
place. Instead, we can safely pass those NUL-terminated char pointers
directly in calls to JNI's NewStringUTF(). NewStringUTF() does not
take ownership of its argument, but rather clones that string data
internally before returning. So using strdup() and delete was just
unnecessary memory churn.
In cases where we need to format, concatenate, or construct new
strings, don't use sprintf() into variable-sized, stack-allocated
arrays. Variable-sized arrays are not portable, and in particular are
rejected by Microsoft's Visual Studio 2017 C++ compiler. Instead, do
our string formatting and manipulations using std::ostringstream
and/or std::string. We just need to be a bit careful about the
lifetimes and ownership responsibilities of allocated data. In
brief, (1) ostringstream::str() returns a temporary string instance
that expires at the end of the enclosing statement, independent of the
lifetime of the ostringstream instance; while (2) string::c_str()
returns an pointer to internal data that remains valid as long as the
string on which it was called is valid and unmodified.
Eclipse's automated code clean-up tool did most of the heavy lifting
here: it specifically has a clean-up option for converting functional
interfaces to lambdas. I merely had to revert the automated changes
for a single enumeration class for which it produced invalid results,
and for a few test inputs that apparently aren't set up to be compiled
with Java 8.
Previously FilterIterator was very permissive regarding the type
relationships between the original iterator, the filtered iterator,
and the predicate used to prune the former down to the latter. Now we
enforce those relationships more strictly, including proper use of
covariant ("<? extends T>") and contravariant ("<? super T>")
polymorphic type parameters where appropriate.
This lets us get rid of seven suppressed warnings about generic types
and/or unchecked conversions. It also moves us toward being able to
use modern Java features like lambdas and streams more easily.
Each of these required careful consideration of what the original
developer *intended* as distinguished from what the developer's code
actually *does*. I believe I got each one right, and WALA's
regression tests agree. A second opinion by a core WALA developer
would be welcome, though.
We already have plenty of examples of Serializable classes with this
field, and the vast majority of those fields have generated IDs rather
than "1L". From this I infer that using proper serialVersionUID
fields is considered appropriate WALA coding style.
Ben Liblit
Julian Dolby
Julian Dolby