[clang] c98d98b - [analyzer] Fix handle leak false positive when the handle dies too early

[Gabor Horvath via cfe-commits]

Author: Gabor Horvath
Date: 2020-01-27T09:52:06-08:00
New Revision: c98d98ba9b0f917385c753becec4ddfef51bc47c

URL: https://github.com/llvm/llvm-project/commit/c98d98ba9b0f917385c753becec4ddfef51bc47c
DIFF: https://github.com/llvm/llvm-project/commit/c98d98ba9b0f917385c753becec4ddfef51bc47c.diff

LOG: [analyzer] Fix handle leak false positive when the handle dies too early

Differential Revision: https://reviews.llvm.org/D73151

Added: 
    

Modified: 
    clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
    clang/test/Analysis/fuchsia_handle.cpp

Removed: 
    


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diff  --git a/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
index 36d4f489214e..3a56a941ff31 100644
--- a/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp
@@ -149,6 +149,10 @@ class HandleState {
       CASE(Kind::Released)
       CASE(Kind::Escaped)
     }
+    if (ErrorSym) {
+      OS << " ErrorSym: ";
+      ErrorSym->dumpToStream(OS);
+    }
   }
 
   LLVM_DUMP_METHOD void dump() const { dump(llvm::errs()); }
@@ -401,7 +405,13 @@ void FuchsiaHandleChecker::checkDeadSymbols(SymbolReaper &SymReaper,
   SmallVector<SymbolRef, 2> LeakedSyms;
   HStateMapTy TrackedHandles = State->get<HStateMap>();
   for (auto &CurItem : TrackedHandles) {
-    if (!SymReaper.isDead(CurItem.first))
+    SymbolRef ErrorSym = CurItem.second.getErrorSym();
+    // Keeping zombie handle symbols. In case the error symbol is dying later
+    // than the handle symbol we might produce spurious leak warnings (in case
+    // we find out later from the status code that the handle allocation failed
+    // in the first place).
+    if (!SymReaper.isDead(CurItem.first) ||
+        (ErrorSym && !SymReaper.isDead(ErrorSym)))
       continue;
     if (CurItem.second.isAllocated() || CurItem.second.maybeAllocated())
       LeakedSyms.push_back(CurItem.first);

diff  --git a/clang/test/Analysis/fuchsia_handle.cpp b/clang/test/Analysis/fuchsia_handle.cpp
index ed8b695a1915..c20622be543f 100644
--- a/clang/test/Analysis/fuchsia_handle.cpp
+++ b/clang/test/Analysis/fuchsia_handle.cpp
@@ -66,6 +66,26 @@ void checkInvalidHandle2() {
     zx_handle_close(sa);
 }
 
+void handleDieBeforeErrorSymbol01() {
+  zx_handle_t sa, sb;
+  zx_status_t status = zx_channel_create(0, &sa, &sb);
+  if (status < 0)
+    return;
+  __builtin_trap();
+}
+
+void handleDieBeforeErrorSymbol02() {
+  zx_handle_t sa, sb;
+  zx_status_t status = zx_channel_create(0, &sa, &sb);
+  // expected-note at -1 {{Handle allocated through 2nd parameter}}
+  if (status == 0) { // expected-note {{Assuming 'status' is equal to 0}}
+                     // expected-note at -1 {{Taking true branch}}
+    return; // expected-warning {{Potential leak of handle}}
+            // expected-note at -1 {{Potential leak of handle}}
+  }
+  __builtin_trap();
+}
+
 void checkNoCrash01() {
   zx_handle_t sa, sb;
   zx_channel_create(0, &sa, &sb);