[llvm-bugs] [Bug 25875] New: differing results between clang-cl and MSVC when preprocessing

Thu Dec 17 14:41:56 PST 2015

https://llvm.org/bugs/show_bug.cgi?id=25875

            Bug ID: 25875
           Summary: differing results between clang-cl and MSVC when
                    preprocessing
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: froydnj at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following test case, reduced from real-world code in Firefox, generates
valid C++ source code when preprocessed with MSVC 2013 (and gcc/clang on Linux)
and produces errors with clang-cl:

/* from configure */
# define JS_CODEGEN_X86 1

/* from mozilla/MacroArgs.h */
#define MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) \
  MOZ_MACROARGS_ARG_COUNT_HELPER((__VA_ARGS__, \
    aPrefix##50, aPrefix##49, aPrefix##48, aPrefix##47, aPrefix##46, \
    aPrefix##45, aPrefix##44, aPrefix##43, aPrefix##42, aPrefix##41, \
    aPrefix##40, aPrefix##39, aPrefix##38, aPrefix##37, aPrefix##36, \
    aPrefix##35, aPrefix##34, aPrefix##33, aPrefix##32, aPrefix##31, \
    aPrefix##30, aPrefix##29, aPrefix##28, aPrefix##27, aPrefix##26, \
    aPrefix##25, aPrefix##24, aPrefix##23, aPrefix##22, aPrefix##21, \
    aPrefix##20, aPrefix##19, aPrefix##18, aPrefix##17, aPrefix##16, \
    aPrefix##15, aPrefix##14, aPrefix##13, aPrefix##12, aPrefix##11, \
    aPrefix##10, aPrefix##9,  aPrefix##8,  aPrefix##7,  aPrefix##6,  \
    aPrefix##5,  aPrefix##4,  aPrefix##3,  aPrefix##2,  aPrefix##1,
aPrefix##0))

#define MOZ_MACROARGS_ARG_COUNT_HELPER(aArgs) \
  MOZ_MACROARGS_ARG_COUNT_HELPER2 aArgs

#define MOZ_MACROARGS_ARG_COUNT_HELPER2( \
   a1,  a2,  a3,  a4,  a5,  a6,  a7,  a8,  a9, a10, \
  a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, \
  a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, \
  a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, \
  a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, \
  a51, ...) a51

/*
 * MOZ_ARGS_AFTER_N expands to its arguments excluding the first |N|
 * arguments. For example:
 *
 *   MOZ_ARGS_AFTER_2(a, b, c, d) expands to: c, d
 */
#define MOZ_ARGS_AFTER_1(a1, ...) __VA_ARGS__
#define MOZ_ARGS_AFTER_2(a1, a2, ...) __VA_ARGS__

/*
 * MOZ_ARG_N expands to its |N|th argument.
 */
#define MOZ_ARG_1(a1, ...) a1
#define MOZ_ARG_2(a1, a2, ...) a2

/* from mozilla/MacroForEach.h */
#define MOZ_FOR_EACH_EXPAND_HELPER(...) __VA_ARGS__
#define MOZ_FOR_EACH_GLUE(a, b) a b
#define MOZ_FOR_EACH(aMacro, aFixedArgs, aArgs) \
  MOZ_FOR_EACH_GLUE( \
    MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_FOR_EACH_, \
                                   MOZ_FOR_EACH_EXPAND_HELPER aArgs), \
    (aMacro, aFixedArgs, aArgs))

#define MOZ_FOR_EACH_HELPER_GLUE(a, b) a b
#define MOZ_FOR_EACH_HELPER(aMacro, aFixedArgs, aArgs) \
  MOZ_FOR_EACH_HELPER_GLUE( \
    aMacro, \
    (MOZ_FOR_EACH_EXPAND_HELPER aFixedArgs MOZ_ARG_1 aArgs))

#define MOZ_FOR_EACH_1(m, fa, a) \
  MOZ_FOR_EACH_HELPER(m, fa, a)
#define MOZ_FOR_EACH_2(m, fa, a) \
  MOZ_FOR_EACH_HELPER(m, fa, a) MOZ_FOR_EACH_1(m, fa, (MOZ_ARGS_AFTER_1 a))

/* from MacroAssembler.h */
# define DEFINED_ON_x86
# define DEFINED_ON_x64
# define DEFINED_ON_x86_shared
# define DEFINED_ON_arm
# define DEFINED_ON_arm64
# define DEFINED_ON_mips32
# define DEFINED_ON_mips64
# define DEFINED_ON_mips_shared
# define DEFINED_ON_none

// Specialize for each architecture.
#if defined(JS_CODEGEN_X86)
# undef DEFINED_ON_x86
# define DEFINED_ON_x86 define
# undef DEFINED_ON_x86_shared
# define DEFINED_ON_x86_shared define
#elif defined(JS_CODEGEN_X64)
# undef DEFINED_ON_x64
# define DEFINED_ON_x64 define
# undef DEFINED_ON_x86_shared
# define DEFINED_ON_x86_shared define
#elif defined(JS_CODEGEN_ARM)
# undef DEFINED_ON_arm
# define DEFINED_ON_arm define
#elif defined(JS_CODEGEN_ARM64)
# undef DEFINED_ON_arm64
# define DEFINED_ON_arm64 define
#elif defined(JS_CODEGEN_MIPS32)
# undef DEFINED_ON_mips32
# define DEFINED_ON_mips32 define
# undef DEFINED_ON_mips_shared
# define DEFINED_ON_mips_shared define
#elif defined(JS_CODEGEN_MIPS64)
# undef DEFINED_ON_mips64
# define DEFINED_ON_mips64 define
# undef DEFINED_ON_mips_shared
# define DEFINED_ON_mips_shared define
#elif defined(JS_CODEGEN_NONE)
# undef DEFINED_ON_none
# define DEFINED_ON_none crash
#else
# error "Unknown architecture!"
#endif

# define DEFINED_ON_RESULT_crash   { MOZ_CRASH(); }
# define DEFINED_ON_RESULT_define
# define DEFINED_ON_RESULT_        = delete

# define DEFINED_ON_DISPATCH_RESULT_2(Macro, Result) \
    Macro ## Result
# define DEFINED_ON_DISPATCH_RESULT(...)     \
    DEFINED_ON_DISPATCH_RESULT_2(DEFINED_ON_RESULT_, __VA_ARGS__)

// We need to let the evaluation of MOZ_FOR_EACH terminate.
# define DEFINED_ON_EXPAND_ARCH_RESULTS_3(ParenResult)  \
    DEFINED_ON_DISPATCH_RESULT ParenResult
# define DEFINED_ON_EXPAND_ARCH_RESULTS_2(ParenResult)  \
    DEFINED_ON_EXPAND_ARCH_RESULTS_3 (ParenResult)
# define DEFINED_ON_EXPAND_ARCH_RESULTS(ParenResult)    \
    DEFINED_ON_EXPAND_ARCH_RESULTS_2 (ParenResult)

# define DEFINED_ON_FWDARCH(Arch) DEFINED_ON_ ## Arch
# define DEFINED_ON_MAP_ON_ARCHS(ArchList)              \
    DEFINED_ON_EXPAND_ARCH_RESULTS(                     \
      (MOZ_FOR_EACH(DEFINED_ON_FWDARCH, (), ArchList)))

# define DEFINED_ON(...)                                \
    DEFINED_ON_MAP_ON_ARCHS((none, __VA_ARGS__))

# define PER_ARCH DEFINED_ON(ALL_ARCH)
# define PER_SHARED_ARCH DEFINED_ON(ALL_SHARED_ARCH)

class Example
{
public:
  Example();

  void arm_only_function() DEFINED_ON(arm);
  void arm64_only_function() DEFINED_ON(arm64);
  void x86_only_function() DEFINED_ON(x86);
};

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