[PATCH] D30312: Fix unix.Malloc analysis crasher when allocating dynamic arrays w/unbound statements (fix PR32050)

[Nico Weber via cfe-commits]

This looks pretty similar to https://reviews.llvm.org/D27849 – are you
synced to trunk?

On Thu, Feb 23, 2017 at 5:42 PM, Kevin Marshall via Phabricator via
cfe-commits <cfe-commits at lists.llvm.org> wrote:

> kmarshall created this revision.
>
> The extent calculation function had a bug which caused it to ignore if the
> size value was defined prior to casting it. As a result, size expressions
> with free variables would trigger assertion failures during the cast
> operation.
>
> This patch adds that missing check, and replaces the redundant call to
> castAs<>() with the SVar that is returned by the checked cast.
>
> Added a regression test "Malloc+NewDynamicArray" that exercises the fix.
>
>
> https://reviews.llvm.org/D30312
>
> Files:
>   lib/StaticAnalyzer/Checkers/MallocChecker.cpp
>   test/Analysis/Malloc+NewDynamicArray.cpp
>
>
> Index: test/Analysis/Malloc+NewDynamicArray.cpp
> ===================================================================
> --- test/Analysis/Malloc+NewDynamicArray.cpp
> +++ test/Analysis/Malloc+NewDynamicArray.cpp
> @@ -0,0 +1,17 @@
> +// RUN: %clang_cc1 -analyze -analyzer-checker=unix.Malloc -verify %s
> +
> +//-----------------------------------------------------------------------
> +// Check that arrays sized using expressions with free variables
> +// do not cause the unix.Malloc checker to crash.
> +//
> +// The function should not actually be called from anywhere, otherwise
> +// the compiler will optimize the length expression and replace it with
> +// with precomputed literals.
> +//-----------------------------------------------------------------------
> +
> +void AllocateExpr(int lhs, int rhs) {
> +  new int[lhs + rhs];
> +}
> +
> +// expected-no-diagnostics
> +
> Index: lib/StaticAnalyzer/Checkers/MallocChecker.cpp
> ===================================================================
> --- lib/StaticAnalyzer/Checkers/MallocChecker.cpp
> +++ lib/StaticAnalyzer/Checkers/MallocChecker.cpp
> @@ -1026,12 +1026,11 @@
>    ASTContext &AstContext = C.getASTContext();
>    CharUnits TypeSize = AstContext.getTypeSizeInChars(ElementType);
>
> -  if (Optional<DefinedOrUnknownSVal> DefinedSize =
> -          ElementCount.getAs<DefinedOrUnknownSVal>()) {
> +  if (Optional<NonLoc> DefinedSize = ElementCount.getAs<NonLoc>()) {
>      DefinedOrUnknownSVal Extent = Region->getExtent(svalBuilder);
>      // size in Bytes = ElementCount*TypeSize
>      SVal SizeInBytes = svalBuilder.evalBinOpNN(
> -        State, BO_Mul, ElementCount.castAs<NonLoc>(),
> +        State, BO_Mul, *DefinedSize,
>          svalBuilder.makeArrayIndex(TypeSize.getQuantity()),
>          svalBuilder.getArrayIndexType());
>      DefinedOrUnknownSVal extentMatchesSize = svalBuilder.evalEQ(
>
>
>
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