r248021 - [analyzer] A fix for substraction of an integer from a pointer.

[Gabor Horvath via cfe-commits]

Author: xazax
Date: Fri Sep 18 14:13:22 2015
New Revision: 248021

URL: http://llvm.org/viewvc/llvm-project?rev=248021&view=rev
Log:
[analyzer] A fix for substraction of an integer from a pointer.

Patch by Artem Dergachev!

Differential Revision: http://reviews.llvm.org/D12725


Modified:
    cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
    cfe/trunk/test/Analysis/ptr-arith.c

Modified: cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp?rev=248021&r1=248020&r2=248021&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp Fri Sep 18 14:13:22 2015
@@ -911,8 +911,9 @@ SVal SimpleSValBuilder::evalBinOpLN(Prog
       elementType = elemReg->getElementType();
     }
     else if (isa<SubRegion>(region)) {
+      assert(op == BO_Add || op == BO_Sub);
+      index = (op == BO_Add) ? rhs : evalMinus(rhs);
       superR = region;
-      index = rhs;
       if (resultTy->isAnyPointerType())
         elementType = resultTy->getPointeeType();
     }

Modified: cfe/trunk/test/Analysis/ptr-arith.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/ptr-arith.c?rev=248021&r1=248020&r2=248021&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/ptr-arith.c (original)
+++ cfe/trunk/test/Analysis/ptr-arith.c Fri Sep 18 14:13:22 2015
@@ -296,3 +296,20 @@ void symbolicFieldRegion(struct Point *p
   clang_analyzer_eval(&points[i].x < &points[i].y);// expected-warning{{TRUE}}
 }
 
+void negativeIndex(char *str) {
+  *(str + 1) = 'a';
+  clang_analyzer_eval(*(str + 1) == 'a'); // expected-warning{{TRUE}}
+  clang_analyzer_eval(*(str - 1) == 'a'); // expected-warning{{UNKNOWN}}
+
+  char *ptr1 = str - 1;
+  clang_analyzer_eval(*ptr1 == 'a'); // expected-warning{{UNKNOWN}}
+
+  char *ptr2 = str;
+  ptr2 -= 1;
+  clang_analyzer_eval(*ptr2 == 'a'); // expected-warning{{UNKNOWN}}
+
+  char *ptr3 = str;
+  --ptr3;
+  clang_analyzer_eval(*ptr3 == 'a'); // expected-warning{{UNKNOWN}}
+}
+