[LLVMbugs] [Bug 18691] New: No -Wtautological-constant-out-of-range-compare warning

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18691

            Bug ID: 18691
           Summary: No -Wtautological-constant-out-of-range-compare
                    warning
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: chengniansun at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

This should be a regression. The trunk does not emit
-Wtautological-constant-out-of-range-compare warnings, whereas, the version 3.3
and 3.4 can. 

Moreover, if I remove the for statement, then the trunk warns. 

$: cat s.c
extern char fn1(char, char);
char func_92() {
  long l_105 = 0;
  for (;; l_105++)
    ;
  return fn1(0, 0) >= 6000;
}
$: clang-trunk -c -Wtautological-constant-out-of-range-compare s.c
$: clang-3.4 -c -Wtautological-constant-out-of-range-compare s.c
s.c:6:20: warning: comparison of constant 6000 with expression of type 'char'
is always false
      [-Wtautological-constant-out-of-range-compare]
  return fn1(0, 0) >= 6000;
         ~~~~~~~~~ ^  ~~~~
1 warning generated.
$: clang-3.3 -c -Wtautological-constant-out-of-range-compare s.c
s.c:6:20: warning: comparison of constant 6000 with expression of type 'char'
is always false
      [-Wtautological-constant-out-of-range-compare]
  return fn1(0, 0) >= 6000;
         ~~~~~~~~~ ^  ~~~~
1 warning generated.
$:
$: clang-trunk -v
clang version 3.5 (trunk 200615)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.1
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.8.1
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0
Selected GCC installation: /usr/lib64/gcc/x86_64-linux-gnu/4.8

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