[analyzer] NFC: Forbid array elements of void type.

Represent the symbolic value for results of pointer arithmetic on void pointers
in a different way: instead of making void-typed element regions, make
char-typed element regions.

Add an assertion that ensures that no void-typed regions are ever constructed.

This is a refactoring of internals that should not immediately affect
the analyzer's (default) behavior.

Differential Revision: https://reviews.llvm.org/D40939

llvm-svn: 322775

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp b/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
index 94d29d5a6ba..0ec4a81af3e 100644
--- a/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
@@ -988,6 +988,12 @@ SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
         elementType = resultTy->getPointeeType();
     }
 
+    // Represent arithmetic on void pointers as arithmetic on char pointers.
+    // It is fine when a TypedValueRegion of char value type represents
+    // a void pointer. Note that arithmetic on void pointers is a GCC extension.
+    if (elementType->isVoidType())
+      elementType = getContext().CharTy;
+
     if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
       return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
                                                        superR, getContext()));