[PATCH] D37478: [analyzer] Implement pointer arithmetic on constants

[Rafael Stahl via Phabricator via cfe-commits]

r.stahl created this revision.
Herald added a subscriber: eraman.

The "Multiplicand" variable in SimpleSValBuilder::evalBinOpLN was always initialized to zero, causing all pointer arithmetic on constant values to be no-ops.

This fixes two FIXMEs in existing tests. The added tests were all failing before this change.


https://reviews.llvm.org/D37478

Files:
  lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
  test/Analysis/explain-svals.cpp
  test/Analysis/inlining/inline-defensive-checks.c
  test/Analysis/pointer-arithmetic.c


Index: test/Analysis/pointer-arithmetic.c
===================================================================
--- test/Analysis/pointer-arithmetic.c
+++ test/Analysis/pointer-arithmetic.c
@@ -0,0 +1,28 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -verify %s
+
+int test1() {
+  int *p = (int *)sizeof(int);
+  p -= 1;
+  return *p; // expected-warning {{Dereference of null pointer}}
+}
+
+int test2() {
+  int *p = (int *)sizeof(int);
+  p -= 2;
+  p += 1;
+  return *p; // expected-warning {{Dereference of null pointer}}
+}
+
+int test3() {
+  int *p = (int *)sizeof(int);
+  p++;
+  p--;
+  p--;
+  return *p; // expected-warning {{Dereference of null pointer}}
+}
+
+int test4() {
+  int *p = 0;
+  p += 1;
+  return *p; // no-warning
+}
Index: test/Analysis/inlining/inline-defensive-checks.c
===================================================================
--- test/Analysis/inlining/inline-defensive-checks.c
+++ test/Analysis/inlining/inline-defensive-checks.c
@@ -159,8 +159,7 @@
 void idcTrackZeroValueThroughUnaryPointerOperatorsWithOffset2(struct S *s) {
   idc(s);
   int *x = &(s->f2) - 1;
-  // FIXME: Should not warn.
-  *x = 7; // expected-warning{{Dereference of null pointer}}
+  *x = 7; // no-warning
 }
 
 void idcTrackZeroValueThroughUnaryPointerOperatorsWithAssignment(struct S *s) {
Index: test/Analysis/explain-svals.cpp
===================================================================
--- test/Analysis/explain-svals.cpp
+++ test/Analysis/explain-svals.cpp
@@ -59,8 +59,7 @@
   clang_analyzer_explain(&s.s2[5].y[3]); // expected-warning-re{{{{^pointer to element of type 'int' with index 3 of field 'y' of base object 'S::S3' inside element of type 'struct S::S2' with index 5 of field 's2' of parameter 's'$}}}}
   if (!s.s2[7].x) {
     clang_analyzer_explain(s.s2[7].x); // expected-warning-re{{{{^concrete memory address '0'$}}}}
-    // FIXME: we need to be explaining '1' rather than '0' here; not explainer bug.
-    clang_analyzer_explain(s.s2[7].x + 1); // expected-warning-re{{{{^concrete memory address '0'$}}}}
+    clang_analyzer_explain(s.s2[7].x + 1); // expected-warning-re{{{{^concrete memory address '4'$}}}}
   }
 }
 
Index: lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
===================================================================
--- lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
+++ lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
@@ -935,6 +935,8 @@
 
       // Offset the increment by the pointer size.
       llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
+      QualType PteeTy = resultTy.getTypePtr()->castAs<PointerType>()->getPointeeType();
+      Multiplicand = getContext().getTypeSizeInChars(PteeTy).getQuantity();
       rightI *= Multiplicand;
 
       // Compute the adjusted pointer.


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