[LLVMbugs] [Bug 2279] New: Conformance problems with pp expressions

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=2279

           Summary: Conformance problems with pp expressions
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: preprocessor
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: neil at daikokuya.co.uk
                CC: llvmbugs at cs.uiuc.edu


These are conformance problems I'm aware of regarding PP expressions.  If you
need a testcase I can provide, but they should be obvious from the
descriptions:

a) Comma subexpressions are permitted in C99 as long as they are unevaluated. 
Clang rejects them, which is correct behaviour for C90 but not C99 (see 6.6).
b) Clang doesn't follow the grammar for the 2nd operand of the conditional
operator.
c) Clang doesn't follow the rules for the signedness of the result of the shift
operators (no UAC).
d) Clang seems to have issues with unevaluated subexpressions.  Here are two
examples:

#if 0 ? 1/0: 2
#else
#error
#endif

#if 1 || 1/0
#else
#error
#endif


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