[LLVMbugs] [Bug 10444] New: False -Wunreachable-code warning in switch(typedefEnum) for default:

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10444

           Summary: False -Wunreachable-code warning in
                    switch(typedefEnum) for default:
           Product: clang
           Version: unspecified
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: john.engelhart at gmail.com
                CC: llvmbugs at cs.uiuc.edu


There is a false -Wunreachable-code warning when a switch() statement has a
`typedef enum` as its argument and all of the declared `enum` types have a
`case ...:` statement for them.

In this case, clang will give an unreachable warning if the `switch() { }`
statement contains a `default:`, which clang will incorrectly warn that the
`default:` case is not reachable.

This is on a Mac OS X 10.7 system running clang from Xcode 4.2 Build 4D75.

shell% uname -a
Darwin anonymous.local 11.0.0 Darwin Kernel Version 11.0.0: Sat Jun 18 12:56:35
PDT 2011; root:xnu-1699.22.73~1/RELEASE_X86_64 x86_64

shell% /Developer4/usr/bin/clang --version
Apple clang version 3.0 (tags/Apple/clang-210.1) (based on LLVM 3.0svn)
Target: x86_64-apple-darwin11.0.0
Thread model: posix

shell% /Developer4/usr/bin/clang -Wunreachable-code -fsyntax-only enumBug.c
enumBug.c:17:7: warning: will never be executed [-Wunreachable-code]
      printf("default, an enum value that is not defined.\n");
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.

// enumBug.c
#include <stdio.h>

typedef enum {
  XYEnumOne,
  XYEnumTwo,
} XYEnumBug;

XYEnumBug enumBug;

int main(int argc, char *argv[]) {
  switch(enumBug) {
    case XYEnumOne:
    case XYEnumTwo:
      printf("a defined enum value\n");
      break;
    default:
      printf("default, an enum value that is not defined.\n");
      break;
  }

  return(0);
}

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