Merge pull request #1702 from mgrettondann/cpp-add-thread_local-support-external

C++: add thread_local support

Author: nickrolfe

change-notes/1.22/analysis-cpp.md

@@ -27,3 +27,4 @@
 - The `semmle.code.cpp.security.TaintTracking` library now considers a pointer difference calculation as blocking taint flow.
 - Fixed the `LocalScopeVariableReachability.qll` library's handling of loops with an entry condition is both always true upon first entry, and where there is more than one control flow path through the loop condition.  This change increases the accuracy of the `LocalScopeVariableReachability.qll` library and queries which depend on it.
 - The `semmle.code.cpp.models` library now models data flow through `std::swap`.
+- There is a new `Variable.isThreadLocal()` predicate. It can be used to tell whether a variable is `thread_local`.

cpp/ql/src/Likely Bugs/Memory Management/ReturnStackAllocatedMemory.ql

@@ -45,6 +45,7 @@ predicate hasNontrivialConversion(Expr e) {
 from LocalScopeVariable var, VariableAccess va, ReturnStmt r
 where
   not var.isStatic() and
+  not var.isThreadLocal() and
   not var.getUnspecifiedType() instanceof ReferenceType and
   not r.isFromUninstantiatedTemplate(_) and
   va = var.getAnAccess() and

cpp/ql/src/semmle/code/cpp/Variable.qll

@@ -139,6 +139,13 @@ class Variable extends Declaration, @variable {
     this.hasSpecifier("is_constexpr")
   }
 
+  /**
+   * Holds if this variable is `thread_local`.
+   */
+  predicate isThreadLocal() {
+    this.hasSpecifier("is_thread_local")
+  }
+
   /**
    * Holds if this variable is constructed from `v` as a result
    * of template instantiation. If so, it originates either from a template

cpp/ql/test/library-tests/clang_ms/element.expected

@@ -88,6 +88,7 @@
 | file://:0:0:0:0 | inline |
 | file://:0:0:0:0 | int |
 | file://:0:0:0:0 | is_constexpr |
+| file://:0:0:0:0 | is_thread_local |
 | file://:0:0:0:0 | long |
 | file://:0:0:0:0 | long double |
 | file://:0:0:0:0 | long long |

cpp/ql/test/library-tests/conditions/elements.expected

@@ -65,6 +65,7 @@
 | file://:0:0:0:0 | inline |
 | file://:0:0:0:0 | int |
 | file://:0:0:0:0 | is_constexpr |
+| file://:0:0:0:0 | is_thread_local |
 | file://:0:0:0:0 | long |
 | file://:0:0:0:0 | long double |
 | file://:0:0:0:0 | long long |

cpp/ql/test/library-tests/templates/instantiations_functions/elements.expected

@@ -113,6 +113,7 @@
 | file://:0:0:0:0 | int & |
 | file://:0:0:0:0 | int * |
 | file://:0:0:0:0 | is_constexpr |
+| file://:0:0:0:0 | is_thread_local |
 | file://:0:0:0:0 | long |
 | file://:0:0:0:0 | long double |
 | file://:0:0:0:0 | long long |

cpp/ql/test/library-tests/unnamed/elements.expected

@@ -58,6 +58,7 @@
 | file://:0:0:0:0 | int * | Other |
 | file://:0:0:0:0 | int[0] | Other |
 | file://:0:0:0:0 | is_constexpr | Other |
+| file://:0:0:0:0 | is_thread_local | Other |
 | file://:0:0:0:0 | long | Other |
 | file://:0:0:0:0 | long double | Other |
 | file://:0:0:0:0 | long long | Other |

cpp/ql/test/library-tests/variables/thread_local/thread_local.cpp

@@ -0,0 +1,7 @@
+
+void returnThreadLocal() {
+  thread_local int threadLocal;
+  int not_threadLocal;
+  static thread_local int threadLocalStatic;
+  extern thread_local int threadLocalExtern;
+}

cpp/ql/test/library-tests/variables/thread_local/thread_local.expected

@@ -0,0 +1,10 @@
+| file://:0:0:0:0 | fp_offset | false |
+| file://:0:0:0:0 | gp_offset | false |
+| file://:0:0:0:0 | overflow_arg_area | false |
+| file://:0:0:0:0 | p#0 | false |
+| file://:0:0:0:0 | p#0 | false |
+| file://:0:0:0:0 | reg_save_area | false |
+| thread_local.cpp:3:20:3:30 | threadLocal | true |
+| thread_local.cpp:4:7:4:21 | not_threadLocal | false |
+| thread_local.cpp:5:27:5:43 | threadLocalStatic | true |
+| thread_local.cpp:6:27:6:43 | threadLocalExtern | true |

cpp/ql/test/library-tests/variables/thread_local/thread_local.ql

@@ -0,0 +1,6 @@
+import cpp
+
+from Variable v
+select v,
+       any(boolean b | if v.isThreadLocal() then b = true else b = false)
+