[PATCH] D26159: [analyzer] MacOSXAPIChecker: Improve warning messages for __block vars in dispatch_once().

Artem Dergachev via cfe-commits cfe-commits at lists.llvm.org
Mon Oct 31 11:51:43 PDT 2016


NoQ created this revision.
NoQ added reviewers: zaks.anna, dcoughlin.
NoQ added a subscriber: cfe-commits.

The checker already warns for `__block`-storage variables being used as a `dispatch_once()` predicate, however it refers to them as local which is not quite accurate, so we fix that.

Also add tests to make sure it works.

FIXME: The analyzer sets stack memory space for `__block` variables when they are referenced outside the block (eg. `test_block_var_from_outside_block()` line 108). Will try to fix in a separate patch; i'm not relying on the memory space in this patch.


https://reviews.llvm.org/D26159

Files:
  lib/StaticAnalyzer/Checkers/MacOSXAPIChecker.cpp
  test/Analysis/dispatch-once.m


Index: test/Analysis/dispatch-once.m
===================================================================
--- test/Analysis/dispatch-once.m
+++ test/Analysis/dispatch-once.m
@@ -90,3 +90,20 @@
 void test_ivar_array_from_external_obj(Object *o) {
   dispatch_once(&o->once_array[1], ^{}); // expected-warning{{Call to 'dispatch_once' uses memory within the instance variable 'once_array' for the predicate value.}}
 }
+
+void test_block_var_from_block() {
+  __block dispatch_once_t once;
+  ^{
+    dispatch_once(&once, ^{}); // expected-warning{{Call to 'dispatch_once' uses the block variable 'once' for the predicate value.}}
+  };
+}
+
+void use_block_var(dispatch_once_t *once);
+
+void test_block_var_from_outside_block() {
+  __block dispatch_once_t once;
+  ^{
+    use_block_var(&once);
+  };
+  dispatch_once(&once, ^{}); // expected-warning{{Call to 'dispatch_once' uses the block variable 'once' for the predicate value.}}
+}
Index: lib/StaticAnalyzer/Checkers/MacOSXAPIChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/MacOSXAPIChecker.cpp
+++ lib/StaticAnalyzer/Checkers/MacOSXAPIChecker.cpp
@@ -94,10 +94,15 @@
   bool SuggestStatic = false;
   os << "Call to '" << FName << "' uses";
   if (const VarRegion *VR = dyn_cast<VarRegion>(RB)) {
-    // We filtered out globals earlier, so it must be a local variable.
+    // We filtered out globals earlier, so it must be a local variable
+    // or a block variable which is under UnknownSpaceRegion.
     if (VR != R)
       os << " memory within";
-    os << " the local variable '" << VR->getDecl()->getName() << '\'';
+    if (VR->getDecl()->hasAttr<BlocksAttr>())
+      os << " the block variable '";
+    else
+      os << " the local variable '";
+    os << VR->getDecl()->getName() << '\'';
     SuggestStatic = true;
   } else if (const ObjCIvarRegion *IVR = getParentIvarRegion(R)) {
     if (IVR != R)
@@ -108,6 +113,9 @@
   } else if (isa<UnknownSpaceRegion>(RS)) {
     // Presence of an IVar superregion has priority over this branch, because
     // ObjC objects are on the heap even if the core doesn't realize this.
+    // Presence of a block variable base region has priority over this branch,
+    // because block variables are known to be either on stack or on heap
+    // (might actually move between the two, hence UnknownSpace).
     return;
   } else {
     os << " stack allocated memory";


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D26159.76453.patch
Type: text/x-patch
Size: 2443 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20161031/dc6e0c88/attachment.bin>


More information about the cfe-commits mailing list