A blog post that shows some of the warnings of the Clang compiler:
http://blog.llvm.org/2013/09/clang-warnings.html
Below I copy from the blog post some of the most interesting of
them, with quotations.
---------------------------------
enum SortType {
unknown = 0,
min_invalid = 3,
bubble = 1,
quick,
insert
};
In this enum, a few non-valid values are defined, then the valid
enums listed. Valid enums use the auto increment to get their
values. However, min_invalid and insert both have value 3.
Luckily, -Wduplicate-enum will identify enums in this situation
and point them out. GCC will not warn on this.
D doesn't warn on this. Perhaps it's good to accept duplicated
enum values only when the user adds some kind of annotation that
denotes a desire for a duplicated value.
---------------------------------
On to sort.cc
Class constructor:
Sort::Sort(int vec[], int size, bool sorted)
: sorted_(sorted_), vec_(vec), size_(size) {
Members from sort.h:
int* vec_;
bool sorted_;
int &size_;
Checking the only constructor of the class, numerous problems can
be seen here. [...] sorted_ is initialized with itself instead of
with sorted. This leads to uninitialized value in sorted_, which
is caught by the aptly named -Wuninitialized. For this case, GCC
has -Wself-assign and -Wself-init.
In bugzilla I have asked for similar tests, like (that is closed):
http://d.puremagic.com/issues/show_bug.cgi?id=4407
Self-assignment is a common mistake that I'd like the D compiler
to catch.
---------------------------------
for (int i = 0; i < size_; ++i) {
for (int j = 1; j < size_; ++i) {
...
}
}
This double nested loop gives bubble sort its n2 running time.
Rather, in this case, an infinite running time. Note the
increment in both of the loops happen on i, even in the inner
loop. j is never touched, either here or inside the loop.
-Wloop-analysis will give a warning when all the variables inside
a for loop conditional does not change during the loop iteration.
Only in Clang.
D has foreach that avoids this bug, but sometimes in D you have
to use for loops (like when the increment is not 1)
void main() {
enum size_ = 5;
for (int i = 0; i < size_; i += 2) {
for (int j = 1; j < size_; i += 2) {}
}
}
See:
http://d.puremagic.com/issues/show_bug.cgi?id=11018
Bye,
bearophile
