[llvm-bugs] [Bug 28872] New: Missing uninitialized variable warning.

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28872

            Bug ID: 28872
           Summary: Missing uninitialized variable warning.
           Product: clang
           Version: unspecified
          Hardware: Macintosh
                OS: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
          Assignee: kremenek at apple.com
          Reporter: mathieu.bosi at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Hi

Code such as:

 int main(void)
 {
   int value = value; // value is garbage, no warning is generated
   return 0;
 }

Does not trigger any warning.

Using the uninitialized value to access an array or any STL container (e.g.
std::map) does not trigger any warnings either.

e.g.
 std::map<int> hashmap;
 int foo = hashmap[foo];


On the other hand, the proper warning appears in code like this:

 int foo(int bar)
 {
   return bar;
 }
 int main(void)
 {
   int value = foo(value); // <-- proper warning is generated
 }

I'm not even sure why C++ allows such syntax (maybe some kind of shortcut for
non plain-old-data / classes?) but it sure caused a (easy to track down) bug in
the code I was working on.

NOTE: I did not know which clang version to select from the Bugzilla spinner.

'clang --version' returns:

 Apple LLVM version 7.3.0 (clang-703.0.31)
 Target: x86_64-apple-darwin15.6.0
 Thread model: posix

Cheers

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