[PATCH] D144780: Explicit cast on customized offsetof should not be ignored when evaluating as const

[Ding Fei via Phabricator via cfe-commits]

danix800 created this revision.
danix800 added a project: clang.
Herald added subscribers: steakhal, martong.
Herald added a reviewer: NoQ.
Herald added a project: All.
danix800 requested review of this revision.
Herald added a subscriber: cfe-commits.

If ignored, the subexpr is a UnaryOperator (&) which cannot be evaluated (assertion failed).

`#define offsetof(type,memb) ((unsigned long)&((type*)0)->memb)`


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D144780

Files:
  clang/lib/StaticAnalyzer/Core/BugReporter.cpp
  clang/test/Analysis/bitwise-ops-nocrash.c


Index: clang/test/Analysis/bitwise-ops-nocrash.c
===================================================================
--- /dev/null
+++ clang/test/Analysis/bitwise-ops-nocrash.c
@@ -0,0 +1,22 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-output=text -triple x86_64-linux-gnu -Wno-shift-count-overflow -verify %s
+
+#define offsetof(type,memb) ((unsigned long)&((type*)0)->memb)
+
+typedef struct {
+  unsigned long guest_counter;
+  unsigned int guest_fpc;
+} S;
+
+// no crash
+int left_shift_overflow_no_crash(unsigned int i) {
+  unsigned shift = 323U; // expected-note{{'shift' initialized to 323}}
+  switch (i) { // expected-note{{Control jumps to 'case 8:'  at line 13}}
+  case offsetof(S, guest_fpc):
+    return 3 << shift; // expected-warning{{The result of the left shift is undefined due to shifting by '323', which is greater or equal to the width of type 'int'}}
+    // expected-note at -1{{The result of the left shift is undefined due to shifting by '323', which is greater or equal to the width of type 'int'}}
+  default:
+    break;
+  }
+
+  return 0;
+}
Index: clang/lib/StaticAnalyzer/Core/BugReporter.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Core/BugReporter.cpp
+++ clang/lib/StaticAnalyzer/Core/BugReporter.cpp
@@ -766,7 +766,7 @@
     case Stmt::CaseStmtClass: {
       os << "Control jumps to 'case ";
       const auto *Case = cast<CaseStmt>(S);
-      const Expr *LHS = Case->getLHS()->IgnoreParenCasts();
+      const Expr *LHS = Case->getLHS()->IgnoreParenImpCasts();
 
       // Determine if it is an enum.
       bool GetRawInt = true;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D144780.500385.patch
Type: text/x-patch
Size: 1645 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20230225/af898353/attachment.bin>