[analyzer] Fix infinite recursion in printing macros

#define f(y) x
#define x f(x)
int main() { x; }

This example results a compilation error since "x" in the first line was not
defined earlier. However, the macro expression printer goes to an infinite
recursion on this example.

Patch by Tibor Brunner!

Differential Revision: https://reviews.llvm.org/D57892

llvm-svn: 354806

clang/lib/StaticAnalyzer/Core/PlistDiagnostics.cpp

@@ -842,6 +842,9 @@ static std::string getMacroNameAndPrintExpansion(TokenPrinter &Printer,
 
   MacroNameAndArgs Info = getMacroNameAndArgs(SM.getExpansionLoc(MacroLoc), PP);
 
+  if (!Info.MI)
+    return Info.Name;
+
   // Manually expand its arguments from the previous macro.
   Info.Args.expandFromPrevMacro(PrevArgs);
 
@@ -936,7 +939,14 @@ static MacroNameAndArgs getMacroNameAndArgs(SourceLocation ExpanLoc,
   assert(II && "Failed to acquire the IndetifierInfo for the macro!");
 
   const MacroInfo *MI = getMacroInfoForLocation(PP, SM, II, ExpanLoc);
-  assert(MI && "The macro must've been defined at it's expansion location!");
+  // assert(MI && "The macro must've been defined at it's expansion location!");
+  //
+  // We should always be able to obtain the MacroInfo in a given TU, but if
+  // we're running the analyzer with CTU, the Preprocessor won't contain the
+  // directive history (or anything for that matter) from another TU.
+  // TODO: assert when we're not running with CTU.
+  if (!MI)
+    return { MacroName, MI, {} };
 
   // Acquire the macro's arguments.
   //