[clang-tools-extra] r298421 - Prevent cppcoreguidelines-pro-bounds-array-to-pointer-decay from diagnosing array to pointer decay stemming from system macros.

[Richard Smith via cfe-commits]

On 21 March 2017 at 12:01, Aaron Ballman via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Author: aaronballman
> Date: Tue Mar 21 14:01:17 2017
> New Revision: 298421
>
> URL: http://llvm.org/viewvc/llvm-project?rev=298421&view=rev
> Log:
> Prevent cppcoreguidelines-pro-bounds-array-to-pointer-decay from
> diagnosing array to pointer decay stemming from system macros.
>
> Patch by Breno Rodrigues Guimaraes.
>
> Modified:
>     clang-tools-extra/trunk/clang-tidy/cppcoreguidelines/
> ProBoundsArrayToPointerDecayCheck.cpp
>     clang-tools-extra/trunk/test/clang-tidy/cppcoreguidelines-
> pro-bounds-array-to-pointer-decay.cpp
>
> Modified: clang-tools-extra/trunk/clang-tidy/cppcoreguidelines/
> ProBoundsArrayToPointerDecayCheck.cpp
> URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/
> trunk/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCh
> eck.cpp?rev=298421&r1=298420&r2=298421&view=diff
> ============================================================
> ==================
> --- clang-tools-extra/trunk/clang-tidy/cppcoreguidelines/
> ProBoundsArrayToPointerDecayCheck.cpp (original)
> +++ clang-tools-extra/trunk/clang-tidy/cppcoreguidelines/
> ProBoundsArrayToPointerDecayCheck.cpp Tue Mar 21 14:01:17 2017
> @@ -47,6 +47,25 @@ AST_MATCHER_P(Expr, hasParentIgnoringImp
>    return InnerMatcher.matches(*E, Finder, Builder);
>  }
>
> +AST_MATCHER(ImplicitCastExpr, isArrayToPointerDecay) {
> +  return Node.getCastKind() == CK_ArrayToPointerDecay;
> +}
> +
> +AST_MATCHER(ImplicitCastExpr, sysSymbolDecayInSysHeader) {
> +  auto &SM = Finder->getASTContext().getSourceManager();
> +  if (SM.isInSystemMacro(Node.getLocStart())) {
> +    if (isa<PredefinedExpr>(Node.getSubExpr()))
> +      return true;
> +
> +    if (const auto *SymbolDeclRef = dyn_cast<DeclRefExpr>(Node.getSubExpr()))
> {
> +      const ValueDecl *SymbolDecl = SymbolDeclRef->getDecl();
> +      if (SymbolDecl && SM.isInSystemHeader(SymbolDecl->getLocation()))
> +        return true;
> +    }
> +  }
> +  return false;
> +}
> +
>  void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder
> *Finder) {
>    if (!getLangOpts().CPlusPlus)
>      return;
> @@ -56,10 +75,12 @@ void ProBoundsArrayToPointerDecayCheck::
>    // 2) inside a range-for over an array
>    // 3) if it converts a string literal to a pointer
>    Finder->addMatcher(
> -      implicitCastExpr(unless(hasParent(arraySubscriptExpr())),
> +      implicitCastExpr(isArrayToPointerDecay(),
> +                       unless(hasParent(arraySubscriptExpr())),
>                         unless(hasParentIgnoringImpCasts(
> explicitCastExpr())),
>                         unless(isInsideOfRangeBeginEndStmt()),
> -                       unless(hasSourceExpression(stringLiteral())))
> +                       unless(hasSourceExpression(stringLiteral())),
> +                       unless(sysSymbolDecayInSysHeader()))
>            .bind("cast"),
>        this);
>  }
> @@ -67,8 +88,6 @@ void ProBoundsArrayToPointerDecayCheck::
>  void ProBoundsArrayToPointerDecayCheck::check(
>      const MatchFinder::MatchResult &Result) {
>    const auto *MatchedCast = Result.Nodes.getNodeAs<
> ImplicitCastExpr>("cast");
> -  if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
> -    return;
>
>    diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into
> a "
>                                    "pointer; consider using
> gsl::array_view or "
>
> Modified: clang-tools-extra/trunk/test/clang-tidy/cppcoreguidelines-
> pro-bounds-array-to-pointer-decay.cpp
> URL: http://llvm.org/viewvc/llvm-project/clang-tools-extra/
> trunk/test/clang-tidy/cppcoreguidelines-pro-bounds-
> array-to-pointer-decay.cpp?rev=298421&r1=298420&r2=298421&view=diff
> ============================================================
> ==================
> --- clang-tools-extra/trunk/test/clang-tidy/cppcoreguidelines-
> pro-bounds-array-to-pointer-decay.cpp (original)
> +++ clang-tools-extra/trunk/test/clang-tidy/cppcoreguidelines-
> pro-bounds-array-to-pointer-decay.cpp Tue Mar 21 14:01:17 2017
> @@ -1,4 +1,5 @@
>  // RUN: %check_clang_tidy %s cppcoreguidelines-pro-bounds-array-to-pointer-decay
> %t
> +#include <assert.h>
>

This test is using a header that we do not supply (unlike stddef.h which
Clang provides itself). That does not seem especially reasonable to me;
this test is failing for us as a result. Can you supply a fake <assert.h>
system header as an input to this test?


>  #include <stddef.h>
>
>  namespace gsl {
> @@ -34,6 +35,11 @@ void f() {
>
>    for (auto &e : a) // OK, iteration internally decays array to pointer
>      e = 1;
> +
> +  assert(false); // OK, array decay inside system header macro
>

Huh? What decay is this referring to?

+
> +  assert(a);
> +  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: do not implicitly decay an
> array into a pointer; consider using gsl::array_view or an explicit cast
> instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay]
>  }
>
>  const char *g() {
>
>
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