[PATCH] D44606: [analyzer] Fix the crash in `IteratorChecker.cpp` when `SymbolConjured` has a null Stmt.

[Henry Wong via Phabricator via cfe-commits]

MTC created this revision.
MTC added reviewers: NoQ, baloghadamsoftware, szepet, dcoughlin.
Herald added subscribers: cfe-commits, a.sidorin, rnkovacs, xazax.hun.
Herald added a reviewer: george.karpenkov.

When the loop has a null terminator statement and sets `widen-loops=true`, `invalidateRegions()` will constructs the
`SymbolConjured` with null `Stmt`. And this will lead to a crash in `IteratorChecker.cpp`.

Given the code below:

  void null_terminator_loop_widen(int *a) {
    int c;
    for (;;) {
      c = *a;
      a++;
    }
  }

I haven't found any problems with `SymbolConjured` containing null `Stmt` for the time being. So I just use 
`dyn_cast_or_null<>` instead of `dyn_cast<>` in `IteratorChecker.cpp`, and didn't delve into the widen loop part.


Repository:
  rC Clang

https://reviews.llvm.org/D44606

Files:
  lib/StaticAnalyzer/Checkers/IteratorChecker.cpp
  test/Analysis/loop-widening.c


Index: test/Analysis/loop-widening.c
===================================================================
--- test/Analysis/loop-widening.c
+++ test/Analysis/loop-widening.c
@@ -1,4 +1,5 @@
 // RUN: %clang_analyze_cc1 -analyzer-checker=core,unix.Malloc,debug.ExprInspection -analyzer-max-loop 4 -analyzer-config widen-loops=true -verify %s
+// RUN: %clang_analyze_cc1 -DTEST_NULL_TERM -analyzer-checker=core,unix.Malloc,debug.ExprInspection,alpha.cplusplus.IteratorRange -analyzer-max-loop 4 -analyzer-config widen-loops=true -verify %s
 
 void clang_analyzer_eval(int);
 void clang_analyzer_warnIfReached();
@@ -188,3 +189,13 @@
   }
   clang_analyzer_eval(i >= 2); // expected-warning {{TRUE}}
 }
+
+#ifdef TEST_NULL_TERM
+void null_terminator_loop_widen(int *a) {
+  int c;
+  for (;;) {
+    c = *a; // no-crash
+    a++;
+  }
+}
+#endif
Index: lib/StaticAnalyzer/Checkers/IteratorChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/IteratorChecker.cpp
+++ lib/StaticAnalyzer/Checkers/IteratorChecker.cpp
@@ -604,7 +604,7 @@
   if (const auto *BSE = dyn_cast<BinarySymExpr>(SE)) {
     return BSE->getOpcode();
   } else if (const auto *SC = dyn_cast<SymbolConjured>(SE)) {
-    const auto *COE = dyn_cast<CXXOperatorCallExpr>(SC->getStmt());
+    const auto *COE = dyn_cast_or_null<CXXOperatorCallExpr>(SC->getStmt());
     if (!COE)
       return BO_Comma; // Extremal value, neither EQ nor NE
     if (COE->getOperator() == OO_EqualEqual) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D44606.138843.patch
Type: text/x-patch
Size: 1507 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20180318/8d7e988f/attachment.bin>