[llvm-bugs] [Bug 35418] New: Analyzer: false-positives about unintialized value

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35418

            Bug ID: 35418
           Summary: Analyzer: false-positives about unintialized value
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Static Analyzer
          Assignee: dcoughlin at apple.com
          Reporter: lebedev.ri at gmail.com
                CC: llvm-bugs at lists.llvm.org

https://godbolt.org/g/5ipje4

Hand-reduced code:
#include <cassert>
void decode(unsigned width) {
  assert(width > 0);

  int base;
  bool inited = false;

  int i = 0;

  if (i % width == 0) {
    base = 512;
    inited = true;
  }

  // assert(inited); // <- if i uncomment this, the warning is gone.
  base+=1;

  if (base >> 10)
    assert(false);
}


I think it should be obvious from the code that `assert(inited);` will always
be reached with `inited == true`.

Also, problem 2: if i replace `base+=1;` with `base++;`, it would no longer
warn there.

For the reference, this is the full original code:
https://github.com/darktable-org/rawspeed/blob/ec958b8550d526ae8904691e96fb34959f69835b/src/librawspeed/decompressors/CrwDecompressor.cpp#L275

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