[analyzer] Unbreak body farms in presence of multiple declarations.

When growing a body on a body farm, it's essential to use the same redeclaration
of the function that's going to be used during analysis. Otherwise our
ParmVarDecls won't match the ones that are used to identify argument regions.

This boils down to trusting the reasoning in AnalysisDeclContext. We shouldn't
canonicalize the declaration before farming the body because it makes us not
obey the sophisticated decision-making process of AnalysisDeclContext.

Differential Revision: https://reviews.llvm.org/D60899

llvm-svn: 358946

clang/lib/Analysis/BodyFarm.cpp

@@ -665,8 +665,6 @@ static Stmt *create_OSAtomicCompareAndSwap(ASTContext &C, const FunctionDecl *D)
 }
 
 Stmt *BodyFarm::getBody(const FunctionDecl *D) {
-  D = D->getCanonicalDecl();
-
   Optional<Stmt *> &Val = Bodies[D];
   if (Val.hasValue())
     return Val.getValue();

clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp

@@ -579,6 +579,9 @@ private:
     PathDiagnosticLocation L =
         PathDiagnosticLocation::create(N->getLocation(), SM);
 
+    // For now this shouldn't trigger, but once it does (as we add more
+    // functions to the body farm), we'll need to decide if these reports
+    // are worth suppressing as well.
     if (!L.hasValidLocation())
       return nullptr;
 

clang/test/Analysis/OSAtomic_mac.c

@@ -8,13 +8,20 @@ int OSAtomicCompareAndSwapPtrBarrier() {
 }
 
 int *invalidSLocOnRedecl() {
-  int *b; // expected-note{{'b' declared without an initial value}}
-
+  // Was crashing when trying to throw a report about returning an uninitialized
+  // value to the caller. FIXME: We should probably still throw that report,
+  // something like "The "compare" part of CompareAndSwap depends on an
+  // undefined value".
+  int *b;
   OSAtomicCompareAndSwapPtrBarrier(0, 0, &b); // no-crash
-  // FIXME: We don't really need these notes.
-  // expected-note@-2{{Calling 'OSAtomicCompareAndSwapPtrBarrier'}}
-  // expected-note@-3{{Returning from 'OSAtomicCompareAndSwapPtrBarrier'}}
-
-  return b; // expected-warning{{Undefined or garbage value returned to caller}}
-            // expected-note@-1{{Undefined or garbage value returned to caller}}
+  return b;
+}
+
+void testThatItActuallyWorks() {
+  void *x = 0;
+  int res = OSAtomicCompareAndSwapPtrBarrier(0, &x, &x);
+  clang_analyzer_eval(res); // expected-warning{{TRUE}}
+                            // expected-note@-1{{TRUE}}
+  clang_analyzer_eval(x == &x); // expected-warning{{TRUE}}
+                                // expected-note@-1{{TRUE}}
 }