[PATCH] D80903: [analyzer] Ignore calculated indices of <= 0 in VLASizeChecker

[Vince Bridgers via Phabricator via cfe-commits]

vabridgers updated this revision to Diff 267882.
vabridgers added a comment.

Address comments from Artem and Balazs. This change just avoids the crash for now until a proper fix can be made.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80903/new/

https://reviews.llvm.org/D80903

Files:
  clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
  clang/test/Analysis/vla.c


Index: clang/test/Analysis/vla.c
===================================================================
--- clang/test/Analysis/vla.c
+++ clang/test/Analysis/vla.c
@@ -137,3 +137,17 @@
   clang_analyzer_eval(clang_analyzer_getExtent(&vla3m) == 2 * x * 4 * sizeof(int));
   // expected-warning at -1{{TRUE}}
 }
+
+// https://bugs.llvm.org/show_bug.cgi?id=46128
+// analyzer doesn't handle more than simple symbolic expressions.
+// Just don't crash.
+extern void foo(void);
+int a;
+void b() {
+  int c = a + 1;
+  for (;;) {
+    int d[c];
+    for (; 0 < c;)
+      foo();
+  }
+} // no-crash
Index: clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp
@@ -126,7 +126,12 @@
       // Size overflow check does not work with symbolic expressions because a
       // overflow situation can not be detected easily.
       uint64_t IndexL = IndexLVal->getZExtValue();
-      assert(IndexL > 0 && "Index length should have been checked for zero.");
+      // FIXME: See https://reviews.llvm.org/D80903 for discussion of
+      // some difference in assume and getKnownValue that leads to
+      // unexpected behavior. Just bail on IndexL == 0 at this point.
+      if (IndexL == 0)
+        return nullptr;
+
       if (KnownSize <= SizeMax / IndexL) {
         KnownSize *= IndexL;
       } else {


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