[CFG] [analyzer] Disable argument construction contexts for variadic functions.

The analyzer doesn't make use of them anyway and they seem to have
pretty weird AST from time to time, so let's just skip them for now.

Fixes pr37769.

Differential Revision: https://reviews.llvm.org/D50824

llvm-svn: 340975

2 files changed, 22 insertions, 2 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index ae7917d6772..48113eb6ba5 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -2421,8 +2421,6 @@ CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
     if (!boundType.isNull()) calleeType = boundType;
   }
 
-  findConstructionContextsForArguments(C);
-
   // If this is a call to a no-return function, this stops the block here.
   bool NoReturn = getFunctionExtInfo(*calleeType).getNoReturn();
 
@@ -2439,6 +2437,13 @@ CFGBlock *CFGBuilder::VisitCallExpr(CallExpr *C, AddStmtChoice asc) {
   bool OmitArguments = false;
 
   if (FunctionDecl *FD = C->getDirectCallee()) {
+    // TODO: Support construction contexts for variadic function arguments.
+    // These are a bit problematic and not very useful because passing
+    // C++ objects as C-style variadic arguments doesn't work in general
+    // (see [expr.call]).
+    if (!FD->isVariadic())
+      findConstructionContextsForArguments(C);
+
     if (FD->isNoReturn() || C->isBuiltinAssumeFalse(*Context))
       NoReturn = true;
     if (FD->hasAttr<NoThrowAttr>())
diff --git a/clang/test/Analysis/cfg-rich-constructors.cpp b/clang/test/Analysis/cfg-rich-constructors.cpp
index ca74b7c93cf..31c306bbfe9 100644
--- a/clang/test/Analysis/cfg-rich-constructors.cpp
+++ b/clang/test/Analysis/cfg-rich-constructors.cpp
@@ -1028,3 +1028,18 @@ void testOperators() {
   C(1) + C(2);
 }
 } // namespace operators
+
+namespace variadic_function_arguments {
+class C {
+ public:
+  C(int);
+};
+
+int variadic(...);
+
+// This code is quite exotic, so let's not test the CFG for it,
+// but only make sure we don't crash.
+void testCrashOnVariadicArgument() {
+  C c(variadic(0 ? c : 0)); // no-crash
+}
+} // namespace variadic_function_arguments