[LLVMbugs] [Bug 19494] New: Incorrect diagnostic issued by -Wunreachable-code for switch case on enums

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Apr 20 08:21:17 PDT 2014


            Bug ID: 19494
           Summary: Incorrect diagnostic issued by -Wunreachable-code for
                    switch case on enums
           Product: clang
           Version: 3.2
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: eyal.lotem at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 12414
  --> http://llvm.org/bugs/attachment.cgi?id=12414&action=edit
Small test case

A comprehensive switch(enum_value) that has a case for each named enum value,
all of which have a "return" confuses clang. It believes that no possible
runtime value is possible besides the named enum values, however this is
incorrect. C (and clang) allow enum-typed variables to be assigned from
non-named values of the enum.

The test case compiles into a correct executable, but if compiled with
-Wunreachable-code, issues an incorrect warning like:

clang -Wunreachable-code -o testclangunreachable testclangunreachable.c &&
testclangunreachable.c:11:12: warning: will never be executed
    printf("Unreachable code reached!\n");
1 warning generated.
Unreachable code reached!

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