[clang][analyzer] Fix crash in loop unrolling

[huang-me]

StaticAnalyzer didn't check if the variable is declared in CompoundStmt under SwitchStmt, which make static analyzer reach root without finding the declaration.

Fixes #68819

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[llvmbot]

@llvm/pr-subscribers-clang

Author: None (huang-me)

Changes

StaticAnalyzer didn't check if the variable is declared in CompoundStmt under SwitchStmt, which make static analyzer reach root without finding the declaration.

Fixes #68819

---

Full diff: https://github.com/llvm/llvm-project/pull/82089.diff

1 Files Affected:

• (modified) clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp (+11)

diff --git a/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp b/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
index a80352816be613..b91dfa26774aa4 100644
--- a/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
+++ b/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
@@ -226,6 +226,17 @@ static bool isPossiblyEscaped(ExplodedNode *N, const DeclRefExpr *DR) {
           return false;
       }
     }
+
+    if (const SwitchStmt *SS = dyn_cast<SwitchStmt>(S)) {
+      for(const Stmt *CB: dyn_cast<CompoundStmt>(SS->getBody())->body()) {
+        for (const Decl *D : dyn_cast<DeclStmt>(CB)->decls()) {
+          // Once we reach the declaration of the VD we can return.
+          if (D->getCanonicalDecl() == VD)
+            return false;
+        }
+      }
+    }
+
     // Check the usage of the pass-by-ref function calls and adress-of operator
     // on VD and reference initialized by VD.
     ASTContext &ASTCtx =

[llvmbot]

@llvm/pr-subscribers-clang-static-analyzer-1

Author: None (huang-me)

Changes

StaticAnalyzer didn't check if the variable is declared in CompoundStmt under SwitchStmt, which make static analyzer reach root without finding the declaration.

Fixes #68819

---

Full diff: https://github.com/llvm/llvm-project/pull/82089.diff

1 Files Affected:

• (modified) clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp (+11)

diff --git a/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp b/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
index a80352816be613..b91dfa26774aa4 100644
--- a/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
+++ b/clang/lib/StaticAnalyzer/Core/LoopUnrolling.cpp
@@ -226,6 +226,17 @@ static bool isPossiblyEscaped(ExplodedNode *N, const DeclRefExpr *DR) {
           return false;
       }
     }
+
+    if (const SwitchStmt *SS = dyn_cast<SwitchStmt>(S)) {
+      for(const Stmt *CB: dyn_cast<CompoundStmt>(SS->getBody())->body()) {
+        for (const Decl *D : dyn_cast<DeclStmt>(CB)->decls()) {
+          // Once we reach the declaration of the VD we can return.
+          if (D->getCanonicalDecl() == VD)
+            return false;
+        }
+      }
+    }
+
     // Check the usage of the pass-by-ref function calls and adress-of operator
     // on VD and reference initialized by VD.
     ASTContext &ASTCtx =

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[NagyDonat]

If I understand it correctly, your change doesn't handle declarations that are in inner statements, e.g. the variable "x" in the following code:

switch (get_value()) {
case 42:
  do {
    int x;
    // ...
  } while (running);
//...
}

Is this compatible with the goals of your commit, or would the original crash remain in a situation like this?

[huang-me]

If I understand it correctly, your change doesn't handle declarations that are in inner statements, e.g. the variable "x" in the following code:

switch (get_value()) {
case 42:
  do {
    int x;
    // ...
  } while (running);
//...
}

Is this compatible with the goals of your commit, or would the original crash remain in a situation like this?

As far as I understand it, the declaration within the CaseStmt would be found before reaching SwitchStmt so I don't think we need to consider this situation.

[NagyDonat]

That sounds reasonable. Unfortunately I don't know much about the context of this change, so let's wait for a review from @danix800 (or somebody else who's knows enough) before merging this change.

Also, perhaps it would be a good idea to add a testcase (or a few of them) in the directory clang/test/Analysis to prevent regressions and illustrate the goals of this change. (As far as I know our test system is just a heap of random C/C++ files with a "how to compile/analyze this" header and "what warnings/errors should appear" markers in comments. I usually add testcases by following the example of older analogous cases.)

[huang-me]

I've added the test case to illustrate the goal of this change.

[steakhal]

Thanks for working on this.
I think iterating the direct child nodes of the switch is fine. I can't think of a better way.

[steakhal]

LGTM

EDIT: Sorry for my late reply.

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