<div dir="ltr">Other than the (fixed) ffmpeg false positive, I see this firing in three places.<div><br></div><div>One of them is in the libc tests for memset and bzero, where the 0 argument is intentional.</div><div>One of them is here: <a href="https://github.com/apache/xerces-c/blob/trunk/src/xercesc/util/XMLUTF16Transcoder.cpp#L114">https://github.com/apache/xerces-c/blob/trunk/src/xercesc/util/XMLUTF16Transcoder.cpp#L114</a> (note that this code is correct).</div><div>And one of them was a real bug where the second and third arguments of memset were transposed.</div><div><br></div><div>That's an extremely low false positive rate, much lower than what we'd expect for an enabled-by-default warning. I find this extremely surprising; I would have expected the ratio of true-- to false-positives to be much much higher. But ultimately data wins out over expectations.</div><div><br></div><div>How does our experience compare to other people's experiences? Are our findings abnormal? (They may well be; our corpus is very C++-heavy.) If this is indeed typical, we should reconsider whether to have these warnings enabled by default, as they do not meet our bar for false positives.</div></div><br><div class="gmail_quote"><div dir="ltr">On Mon, 23 Jul 2018 at 09:28, Erik Pilkington via cfe-commits <<a href="mailto:cfe-commits@lists.llvm.org">cfe-commits@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
  
    
  
  <div text="#000000" bgcolor="#FFFFFF">
    <p>Sure, that seems pretty reasonable. r337706. Thanks for the
      suggestion!</p>
    <br>
    <div class="m_8770740850700139232moz-cite-prefix">On 7/21/18 1:40 PM, Arthur O'Dwyer
      wrote:<br>
    </div>
    <blockquote type="cite">
      
      <div dir="ltr">
        <div>In this case Clang is complaining about</div>
        <div><br>
        </div>
        <div>    memset(complicated-expr, 0, 0);</div>
        <div><br>
        </div>
        <div>which means that transposing the last two arguments would
          not "fix" anything. Clang ought to not complain in this case.</div>
        <div>It doesn't have anything to do with coming from a macro;
          it's just that <i>both</i> arguments are zero.</div>
        <div>(I would also expect that `memset(complicated-expr,
          (unsigned char)fill, (size_t)0)` shouldn't warn, either. But
          we had some disagreement that casts to `(unsigned char)` resp.
          `(size_t)` should be the right way to shut up the warning in
          the first place...)</div>
        <div>Basically Clang should only be suggesting a swap (and thus
          complaining at all) in the case that swapping the arguments
          would actually improve the situation.</div>
        <div><br>
        </div>
        <div>–Arthur</div>
        <div><br>
        </div>
        On Sat, Jul 21, 2018 at 1:33 PM, Nico Weber via cfe-commits <span dir="ltr"><<a href="mailto:cfe-commits@lists.llvm.org" target="_blank">cfe-commits@lists.llvm.org</a>></span>
        wrote:<br>
        <div class="gmail_extra">
          <div class="gmail_quote">
            <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
              <div dir="ltr">This has a false positive on ffmpeg:<br>
                <div><br>
                </div>
                <div>
                  <div>../../third_party/ffmpeg/libavcodec/options.c:273:64:
                    error: 'size' argument to memset is '0'; did you
                    mean to transpose the last two arguments?
                    [-Werror,-Wmemset-transposed-args]</div>
                  <div>alloc_and_copy_or_fail(intra_matrix, 64 *
                    sizeof(int16_t), 0);</div>
                </div>
                <div><br>
                </div>
                <div>With:</div>
                <div><br>
                </div>
                <div>
                  <div>#define alloc_and_copy_or_fail(obj, size, pad) \</div>
                  <div>    if (src->obj && size > 0) { \</div>
                  <div>        dest->obj = av_malloc(size + pad); \</div>
                  <div>        if (!dest->obj) \</div>
                  <div>            goto fail; \</div>
                  <div>        memcpy(dest->obj, src->obj, size);
                    \</div>
                  <div>        if (pad) \</div>
                  <div>            memset(((uint8_t *) dest->obj) +
                    size, 0, pad); \</div>
                  <div>    }</div>
                </div>
                <div><br>
                </div>
                <div>(<a href="https://cs.chromium.org/chromium/src/third_party/ffmpeg/libavcodec/options.c?q=alloc_and_copy_or_fail&sq=package:chromium&g=0&l=261" target="_blank">https://cs.chromium.org/chromium/src/third_party/ffmpeg/libavcodec/options.c?q=alloc_and_copy_or_fail&sq=package:chromium&g=0&l=261</a>
                  ; <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=866202" target="_blank">https://bugs.chromium.org/p/chromium/issues/detail?id=866202</a>)</div>
                <div><br>
                </div>
                <div>Maybe the warning shouldn't fire if the memset is
                  from a macro?</div>
              </div>
              <br>
              <div class="gmail_quote">
                <div dir="ltr">On Thu, Jul 19, 2018 at 12:51 PM Erik
                  Pilkington via cfe-commits <<a href="mailto:cfe-commits@lists.llvm.org" target="_blank">cfe-commits@lists.llvm.org</a>>
                  wrote:<br>
                </div>
                <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author:
                  epilk<br>
                  Date: Thu Jul 19 09:46:15 2018<br>
                  New Revision: 337470<br>
                  <br>
                  URL: <a href="http://llvm.org/viewvc/llvm-project?rev=337470&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=337470&view=rev</a><br>
                  Log:<br>
                  [Sema] Add a new warning, -Wmemset-transposed-args<br>
                  <br>
                  This diagnoses calls to memset that have the second
                  and third arguments<br>
                  transposed, for example:<br>
                  <br>
                    memset(buf, sizeof(buf), 0);<br>
                  <br>
                  This is done by checking if the third argument is a
                  literal 0, or if the second<br>
                  is a sizeof expression (and the third isn't). The
                  first check is also done for<br>
                  calls to bzero.<br>
                  <br>
                  Differential revision: <a href="https://reviews.llvm.org/D49112" rel="noreferrer" target="_blank">https://reviews.llvm.org/D49112</a><br>
                  <br>
                  Added:<br>
                      cfe/trunk/test/Sema/transpose-memset.c<br>
                  Modified:<br>
                      cfe/trunk/include/clang/Basic/DiagnosticGroups.td<br>
                      cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td<br>
                      cfe/trunk/lib/Sema/SemaChecking.cpp<br>
                  <br>
                  Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td<br>
                  URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=337470&r1=337469&r2=337470&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=337470&r1=337469&r2=337470&view=diff</a><br>
                  ==============================================================================<br>
                  --- cfe/trunk/include/clang/Basic/DiagnosticGroups.td
                  (original)<br>
                  +++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td
                  Thu Jul 19 09:46:15 2018<br>
                  @@ -443,6 +443,13 @@ def : DiagGroup<"synth">;<br>
                   def SizeofArrayArgument : DiagGroup<"sizeof-array-argument">;<br>
                   def SizeofArrayDecay :
                  DiagGroup<"sizeof-array-decay">;<br>
                   def SizeofPointerMemaccess :
                  DiagGroup<"sizeof-pointer-memaccess">;<br>
                  +def MemsetTransposedArgs :
                  DiagGroup<"memset-transposed-args">;<br>
                  +def DynamicClassMemaccess :
                  DiagGroup<"dynamic-class-memaccess">;<br>
                  +def NonTrivialMemaccess : DiagGroup<"nontrivial-memaccess">;<br>
                  +def SuspiciousBzero :
                  DiagGroup<"suspicious-bzero">;<br>
                  +def SuspiciousMemaccess : DiagGroup<"suspicious-memaccess",<br>
                  +  [SizeofPointerMemaccess, DynamicClassMemaccess,<br>
                  +   NonTrivialMemaccess, MemsetTransposedArgs,
                  SuspiciousBzero]>;<br>
                   def StaticInInline :
                  DiagGroup<"static-in-inline">;<br>
                   def StaticLocalInInline :
                  DiagGroup<"static-local-in-inline">;<br>
                   def GNUStaticFloatInit :
                  DiagGroup<"gnu-static-float-init">;<br>
                  <br>
                  Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td<br>
                  URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=337470&r1=337469&r2=337470&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=337470&r1=337469&r2=337470&view=diff</a><br>
                  ==============================================================================<br>
                  --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
                  (original)<br>
                  +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
                  Thu Jul 19 09:46:15 2018<br>
                  @@ -619,14 +619,14 @@ def warn_cstruct_memaccess :
                  Warning<<br>
                     "%select{destination for|source of|first operand
                  of|second operand of}0 this "<br>
                     "%1 call is a pointer to record %2 that is not
                  trivial to "<br>
                     "%select{primitive-default-initialize|primitive-copy}3">,<br>
                  -  InGroup<DiagGroup<"nontrivial-memaccess">>;<br>
                  +  InGroup<NonTrivialMemaccess>;<br>
                   def note_nontrivial_field : Note<<br>
                     "field is non-trivial to %select{copy|default-initialize}0">;<br>
                   def warn_dyn_class_memaccess : Warning<<br>
                     "%select{destination for|source of|first operand
                  of|second operand of}0 this "<br>
                     "%1 call is a pointer to %select{|class containing
                  a }2dynamic class %3; "<br>
                     "vtable pointer will be %select{overwritten|copied|moved|compared}4">,<br>
                  -  InGroup<DiagGroup<"dynamic-class-memaccess">>;<br>
                  +  InGroup<DynamicClassMemaccess>;<br>
                   def note_bad_memaccess_silence : Note<<br>
                     "explicitly cast the pointer to silence this
                  warning">;<br>
                   def warn_sizeof_pointer_expr_memaccess :
                  Warning<<br>
                  @@ -655,7 +655,19 @@ def note_memsize_comparison_paren
                  : Note<br>
                     "did you mean to compare the result of %0
                  instead?">;<br>
                   def note_memsize_comparison_cast_silence :
                  Note<<br>
                     "explicitly cast the argument to size_t to silence
                  this warning">;<br>
                  -  <br>
                  +def warn_suspicious_sizeof_memset : Warning<<br>
                  +  "%select{'size' argument to memset is '0'|"<br>
                  +  "setting buffer to a 'sizeof' expression}0"<br>
                  +  "; did you mean to transpose the last two
                  arguments?">,<br>
                  +  InGroup<MemsetTransposedArgs>;<br>
                  +def note_suspicious_sizeof_memset_silence :
                  Note<<br>
                  +  "%select{parenthesize the third argument|"<br>
                  +  "cast the second argument to 'int'}0 to
                  silence">;<br>
                  +def warn_suspicious_bzero_size : Warning<"'size'
                  argument to bzero is '0'">,<br>
                  +  InGroup<SuspiciousBzero>;<br>
                  +def note_suspicious_bzero_size_silence :
                  Note<<br>
                  +  "parenthesize the second argument to silence">;<br>
                  +<br>
                   def warn_strncat_large_size : Warning<<br>
                     "the value of the size argument in 'strncat' is too
                  large, might lead to a " <br>
                     "buffer overflow">, InGroup<StrncatSize>;<br>
                  <br>
                  Modified: cfe/trunk/lib/Sema/SemaChecking.cpp<br>
                  URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=337470&r1=337469&r2=337470&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=337470&r1=337469&r2=337470&view=diff</a><br>
                  ==============================================================================<br>
                  --- cfe/trunk/lib/Sema/SemaChecking.cpp
                  (original)<br>
                  +++ cfe/trunk/lib/Sema/SemaChecking.cpp Thu Jul
                  19 09:46:15 2018<br>
                  @@ -8629,24 +8629,26 @@ static const CXXRecordDecl
                  *getContained<br>
                     return nullptr;<br>
                   }<br>
                  <br>
                  +static const UnaryExprOrTypeTraitExpr
                  *getAsSizeOfExpr(const Expr *E) {<br>
                  +  if (const auto *Unary = dyn_cast<UnaryExprOrTypeTraitExpr>(E))<br>
                  +    if (Unary->getKind() == UETT_SizeOf)<br>
                  +      return Unary;<br>
                  +  return nullptr;<br>
                  +}<br>
                  +<br>
                   /// If E is a sizeof expression, returns its argument
                  expression,<br>
                   /// otherwise returns NULL.<br>
                   static const Expr *getSizeOfExprArg(const Expr *E) {<br>
                  -  if (const UnaryExprOrTypeTraitExpr *SizeOf =<br>
                  -      dyn_cast<UnaryExprOrTypeTraitExpr>(E))<br>
                  -    if (SizeOf->getKind() == UETT_SizeOf
                  && !SizeOf->isArgumentType())<br>
                  +  if (const UnaryExprOrTypeTraitExpr *SizeOf =
                  getAsSizeOfExpr(E))<br>
                  +    if (!SizeOf->isArgumentType())<br>
                         return SizeOf->getArgumentExpr()->IgnoreParenImpCasts();<br>
                  -<br>
                     return nullptr;<br>
                   }<br>
                  <br>
                   /// If E is a sizeof expression, returns its argument
                  type.<br>
                   static QualType getSizeOfArgType(const Expr *E) {<br>
                  -  if (const UnaryExprOrTypeTraitExpr *SizeOf =<br>
                  -      dyn_cast<UnaryExprOrTypeTraitExpr>(E))<br>
                  -    if (SizeOf->getKind() == UETT_SizeOf)<br>
                  -      return SizeOf->getTypeOfArgument();<br>
                  -<br>
                  +  if (const UnaryExprOrTypeTraitExpr *SizeOf =
                  getAsSizeOfExpr(E))<br>
                  +    return SizeOf->getTypeOfArgument();<br>
                     return QualType();<br>
                   }<br>
                  <br>
                  @@ -8742,6 +8744,86 @@ struct
                  SearchNonTrivialToCopyField<br>
                  <br>
                   }<br>
                  <br>
                  +/// Detect if \c SizeofExpr is likely to calculate
                  the sizeof an object.<br>
                  +static bool doesExprLikelyComputeSize(const Expr
                  *SizeofExpr) {<br>
                  +  SizeofExpr = SizeofExpr->IgnoreParenImpCasts();<br>
                  +<br>
                  +  if (const auto *BO =
                  dyn_cast<BinaryOperator>(SizeofExpr)) {<br>
                  +    if (BO->getOpcode() != BO_Mul &&
                  BO->getOpcode() != BO_Add)<br>
                  +      return false;<br>
                  +<br>
                  +    return doesExprLikelyComputeSize(BO->getLHS())
                  ||<br>
                  +           doesExprLikelyComputeSize(BO->getRHS());<br>
                  +  }<br>
                  +<br>
                  +  return getAsSizeOfExpr(SizeofExpr) != nullptr;<br>
                  +}<br>
                  +<br>
                  +/// Check if the ArgLoc originated from a macro
                  passed to the call at CallLoc.<br>
                  +///<br>
                  +/// \code<br>
                  +///   #define MACRO 0<br>
                  +///   foo(MACRO);<br>
                  +///   foo(0);<br>
                  +/// \endcode<br>
                  +///<br>
                  +/// This should return true for the first call to
                  foo, but not for the second<br>
                  +/// (regardless of whether foo is a macro or
                  function).<br>
                  +static bool isArgumentExpandedFromMacro(SourceManager
                  &SM,<br>
                  +                                       
                  SourceLocation CallLoc,<br>
                  +                                       
                  SourceLocation ArgLoc) {<br>
                  +  if (!CallLoc.isMacroID())<br>
                  +    return SM.getFileID(CallLoc) !=
                  SM.getFileID(ArgLoc);<br>
                  +<br>
                  +  return SM.getFileID(SM.getImmediateMacroCallerLoc(CallLoc))
                  !=<br>
                  +         SM.getFileID(SM.getImmediateMacroCallerLoc(ArgLoc));<br>
                  +}<br>
                  +<br>
                  +/// Diagnose cases like 'memset(buf, sizeof(buf),
                  0)', which should have the<br>
                  +/// last two arguments transposed.<br>
                  +static void CheckMemaccessSize(Sema &S, unsigned
                  BId, const CallExpr *Call) {<br>
                  +  if (BId != Builtin::BImemset && BId !=
                  Builtin::BIbzero)<br>
                  +    return;<br>
                  +<br>
                  +  const Expr *SizeArg =<br>
                  +    Call->getArg(BId == Builtin::BImemset ? 2 :
                  1)->IgnoreImpCasts();<br>
                  +<br>
                  +  // If we're memsetting or bzeroing 0 bytes, then
                  this is likely an error.<br>
                  +  SourceLocation CallLoc = Call->getRParenLoc();<br>
                  +  SourceManager &SM = S.getSourceManager();<br>
                  +  if (isa<IntegerLiteral>(SizeArg) &&<br>
                  +      cast<IntegerLiteral>(SizeArg)->getValue()
                  == 0 &&<br>
                  +      !isArgumentExpandedFromMacro(SM, CallLoc,
                  SizeArg->getExprLoc())) {<br>
                  +<br>
                  +    SourceLocation DiagLoc =
                  SizeArg->getExprLoc();<br>
                  +<br>
                  +    // Some platforms #define bzero to
                  __builtin_memset. See if this is the<br>
                  +    // case, and if so, emit a better diagnostic.<br>
                  +    if (BId == Builtin::BIbzero ||<br>
                  +        (CallLoc.isMacroID() &&
                  Lexer::getImmediateMacroName(<br>
                  +                                    CallLoc, SM,
                  S.getLangOpts()) == "bzero")) {<br>
                  +      S.Diag(DiagLoc, diag::warn_suspicious_bzero_size);<br>
                  +      S.Diag(DiagLoc, diag::note_suspicious_bzero_size_silence);<br>
                  +    } else {<br>
                  +      S.Diag(DiagLoc, diag::warn_suspicious_sizeof_memset)
                  << 0;<br>
                  +      S.Diag(DiagLoc, diag::note_suspicious_sizeof_memset_silence)
                  << 0;<br>
                  +    }<br>
                  +    return;<br>
                  +  }<br>
                  +<br>
                  +  // If the second argument to a memset is a sizeof
                  expression and the third<br>
                  +  // isn't, this is also likely an error. This should
                  catch<br>
                  +  // 'memset(buf, sizeof(buf), 0xff)'.<br>
                  +  if (BId == Builtin::BImemset &&<br>
                  +      doesExprLikelyComputeSize(Call->getArg(1))
                  &&<br>
                  +      !doesExprLikelyComputeSize(Call->getArg(2)))
                  {<br>
                  +    SourceLocation DiagLoc =
                  Call->getArg(1)->getExprLoc();<br>
                  +    S.Diag(DiagLoc, diag::warn_suspicious_sizeof_memset)
                  << 1;<br>
                  +    S.Diag(DiagLoc, diag::note_suspicious_sizeof_memset_silence)
                  << 1;<br>
                  +    return;<br>
                  +  }<br>
                  +}<br>
                  +<br>
                   /// Check for dangerous or invalid arguments to
                  memset().<br>
                   ///<br>
                   /// This issues warnings on known problematic,
                  dangerous or unspecified<br>
                  @@ -8771,6 +8853,9 @@ void
                  Sema::CheckMemaccessArguments(const<br>
                                                       
                  Call->getLocStart(), Call->getRParenLoc()))<br>
                       return;<br>
                  <br>
                  +  // Catch cases like 'memset(buf, sizeof(buf), 0)'.<br>
                  +  CheckMemaccessSize(*this, BId, Call);<br>
                  +<br>
                     // We have special checking when the length is a
                  sizeof expression.<br>
                     QualType SizeOfArgTy = getSizeOfArgType(LenExpr);<br>
                     const Expr *SizeOfArg = getSizeOfExprArg(LenExpr);<br>
                  <br>
                  Added: cfe/trunk/test/Sema/transpose-memset.c<br>
                  URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/transpose-memset.c?rev=337470&view=auto" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/transpose-memset.c?rev=337470&view=auto</a><br>
                  ==============================================================================<br>
                  --- cfe/trunk/test/Sema/transpose-memset.c
                  (added)<br>
                  +++ cfe/trunk/test/Sema/transpose-memset.c Thu
                  Jul 19 09:46:15 2018<br>
                  @@ -0,0 +1,60 @@<br>
                  +// RUN: %clang_cc1       -Wmemset-transposed-args
                  -verify %s<br>
                  +// RUN: %clang_cc1 -xc++ -Wmemset-transposed-args
                  -verify %s<br>
                  +<br>
                  +#define memset(...) __builtin_memset(__VA_ARGS__)<br>
                  +#define bzero(x,y) __builtin_memset(x, 0, y)<br>
                  +#define real_bzero(x,y) __builtin_bzero(x,y)<br>
                  +<br>
                  +int array[10];<br>
                  +int *ptr;<br>
                  +<br>
                  +int main() {<br>
                  +  memset(array, sizeof(array), 0); //
                  expected-warning{{'size' argument to memset is '0';
                  did you mean to transpose the last two arguments?}}
                  expected-note{{parenthesize the third argument to
                  silence}}<br>
                  +  memset(array, sizeof(array), 0xff); //
                  expected-warning{{setting buffer to a 'sizeof'
                  expression; did you mean to transpose the last two
                  arguments?}} expected-note{{cast the second argument
                  to 'int' to silence}}<br>
                  +  memset(ptr, sizeof(ptr), 0); //
                  expected-warning{{'size' argument to memset is '0';
                  did you mean to transpose the last two arguments?}}
                  expected-note{{parenthesize the third argument to
                  silence}}<br>
                  +  memset(ptr, sizeof(*ptr) * 10, 1); //
                  expected-warning{{setting buffer to a 'sizeof'
                  expression; did you mean to transpose the last two
                  arguments?}} expected-note{{cast the second argument
                  to 'int' to silence}}<br>
                  +  memset(ptr, 10 * sizeof(int *), 1); //
                  expected-warning{{setting buffer to a 'sizeof'
                  expression; did you mean to transpose the last two
                  arguments?}} expected-note{{cast the second argument
                  to 'int' to silence}}<br>
                  +  memset(ptr, 10 * sizeof(int *) + 10, 0xff); //
                  expected-warning{{setting buffer to a 'sizeof'
                  expression; did you mean to transpose the last two
                  arguments?}} expected-note{{cast the second argument
                  to 'int' to silence}}<br>
                  +  memset(ptr, sizeof(char) * sizeof(int *), 0xff); //
                  expected-warning{{setting buffer to a 'sizeof'
                  expression; did you mean to transpose the last two
                  arguments?}} expected-note{{cast the second argument
                  to 'int' to silence}}<br>
                  +  memset(array, sizeof(array), sizeof(array)); //
                  Uh... fine I guess.<br>
                  +  memset(array, 0, sizeof(array));<br>
                  +  memset(ptr, 0, sizeof(int *) * 10);<br>
                  +  memset(array, (int)sizeof(array), (0)); // no
                  warning<br>
                  +  memset(array, (int)sizeof(array), 32); // no
                  warning<br>
                  +  memset(array, 32, (0)); // no warning<br>
                  +<br>
                  +  bzero(ptr, 0); // expected-warning{{'size' argument
                  to bzero is '0'}} expected-note{{parenthesize the
                  second argument to silence}}<br>
                  +  real_bzero(ptr, 0); // expected-warning{{'size'
                  argument to bzero is '0'}} expected-note{{parenthesize
                  the second argument to silence}}<br>
                  +}<br>
                  +<br>
                  +void macros() {<br>
                  +#define ZERO 0<br>
                  +  int array[10];<br>
                  +  memset(array, 0xff, ZERO); // no warning<br>
                  +  // Still emit a diagnostic for memsetting a sizeof
                  expression:<br>
                  +  memset(array, sizeof(array), ZERO); //
                  expected-warning{{'sizeof'}} expected-note{{cast}}<br>
                  +  bzero(array, ZERO); // no warning<br>
                  +  real_bzero(array, ZERO); // no warning<br>
                  +#define NESTED_DONT_DIAG                        \<br>
                  +  memset(array, 0xff, ZERO);                    \<br>
                  +  real_bzero(array, ZERO);<br>
                  +<br>
                  +  NESTED_DONT_DIAG;<br>
                  +<br>
                  +#define NESTED_DO_DIAG                          \<br>
                  +  memset(array, 0xff, 0);                       \<br>
                  +  real_bzero(array, 0)<br>
                  +<br>
                  +  NESTED_DO_DIAG; // expected-warning{{'size'
                  argument to memset}} expected-warning{{'size' argument
                  to bzero}} expected-note2{{parenthesize}}<br>
                  +<br>
                  +#define FN_MACRO(p)                             \<br>
                  +  memset(array, 0xff, p)<br>
                  +<br>
                  +  FN_MACRO(ZERO);<br>
                  +  FN_MACRO(0); // FIXME: should we diagnose this?<br>
                  +<br>
                  +  __builtin_memset(array, 0, ZERO); // no warning<br>
                  +  __builtin_bzero(array, ZERO);<br>
                  +  __builtin_memset(array, 0, 0); //
                  expected-warning{{'size' argument to memset}} //
                  expected-note{{parenthesize}}<br>
                  +  __builtin_bzero(array, 0); //
                  expected-warning{{'size' argument to bzero}} //
                  expected-note{{parenthesize}}<br>
                  +}<br>
                  <br>
                  <br>
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