[LLVMbugs] [Bug 19020] New: -Wunreachable-code should not complain about unreachable declarations.

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=19020

            Bug ID: 19020
           Summary: -Wunreachable-code should not complain about
                    unreachable declarations.
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: scshunt at csclub.uwaterloo.ca
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Consider the following example:

scshunt at orolo:~$ clang -x c -Wunreachable-code -
void foo(int i) {
  switch(i) {
    int j;
  case 1:
    j = 4; 
    j *= 6;
  default:
    return;
  }
}
<stdin>:3:5: warning: will never be executed [-Wunreachable-code]
    int j;
    ^~~~~~
1 warning generated.

In this case, the fact that the declaration is never reached is not a problem,
because the declaration doesn't actually execute any code, and the compiler
still needs to ensure that when it jumps to the label, the stack pointer is
updated correctly.

If the variable is initialized, then the initializer will be skipped, and this
should perhaps be a separate warning, but that's a different issue.

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