Index: lib/StaticAnalyzer/Core/PathDiagnostic.cpp
===================================================================
--- lib/StaticAnalyzer/Core/PathDiagnostic.cpp
+++ lib/StaticAnalyzer/Core/PathDiagnostic.cpp
@@ -406,11 +406,15 @@
   std::pair<bool, bool> InSameTU = SM.isInTheSameTranslationUnit(XOffs, YOffs);
   if (InSameTU.first)
     return XL.isBeforeInTranslationUnitThan(YL);
-  const FileEntry *XFE = SM.getFileEntryForID(XL.getFileID());
-  const FileEntry *YFE = SM.getFileEntryForID(YL.getFileID());
+  const FileEntry *XFE = SM.getFileEntryForID(XL.getSpellingLoc().getFileID());
+  const FileEntry *YFE = SM.getFileEntryForID(YL.getSpellingLoc().getFileID());
   if (!XFE || !YFE)
     return XFE && !YFE;
-  return XFE->getName() < YFE->getName();
+  int NameCmp = XFE->getName().compare(YFE->getName());
+  if (NameCmp != 0)
+    return NameCmp == -1;
+  // Last resort: Compare raw file IDs that are possibly expansions.
+  return XL.getFileID() < YL.getFileID();
 }
 
 static bool compare(const PathDiagnostic &X, const PathDiagnostic &Y) {
Index: test/Analysis/Inputs/ctu-other.cpp
===================================================================
--- test/Analysis/Inputs/ctu-other.cpp
+++ test/Analysis/Inputs/ctu-other.cpp
@@ -1,3 +1,5 @@
+#include "../ctu-hdr.h"
+
 int callback_to_main(int x);
 int f(int x) {
   return x - 1;
@@ -68,3 +70,8 @@
 
 typedef struct { int n; } Anonymous;
 int fun_using_anon_struct(int n) { Anonymous anon; anon.n = n; return anon.n; }
+
+int other_macro_diag(int x) {
+  MACRODIAG();
+  return x;
+}
Index: test/Analysis/Inputs/externalFnMap.txt
===================================================================
--- test/Analysis/Inputs/externalFnMap.txt
+++ test/Analysis/Inputs/externalFnMap.txt
@@ -12,3 +12,4 @@
 c:@N@chns@S@chcls@F@chf4#I# ctu-chain.cpp.ast
 c:@N@chns@F@chf2#I# ctu-chain.cpp.ast
 c:@F@fun_using_anon_struct#I# ctu-other.cpp.ast
+c:@F@other_macro_diag#I# ctu-other.cpp.ast
Index: test/Analysis/ctu-hdr.h
===================================================================
--- test/Analysis/ctu-hdr.h
+++ test/Analysis/ctu-hdr.h
@@ -0,0 +1,3 @@
+#define MACRODIAG() clang_analyzer_warnIfReached()
+
+void clang_analyzer_warnIfReached();
Index: test/Analysis/ctu-main.cpp
===================================================================
--- test/Analysis/ctu-main.cpp
+++ test/Analysis/ctu-main.cpp
@@ -4,6 +4,8 @@
 // RUN: cp %S/Inputs/externalFnMap.txt %T/ctudir/
 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -analyze -analyzer-checker=core,debug.ExprInspection -analyzer-config experimental-enable-naive-ctu-analysis=true -analyzer-config ctu-dir=%T/ctudir -verify %s
 
+#include "ctu-hdr.h"
+
 void clang_analyzer_eval(int);
 
 int f(int);
@@ -41,6 +43,7 @@
 }
 
 int fun_using_anon_struct(int);
+int other_macro_diag(int);
 
 int main() {
   clang_analyzer_eval(f(3) == 2); // expected-warning{{TRUE}}
@@ -58,4 +61,8 @@
 
   clang_analyzer_eval(chns::chf1(4) == 12); // expected-warning{{TRUE}}
   clang_analyzer_eval(fun_using_anon_struct(8) == 8); // expected-warning{{TRUE}}
+
+  clang_analyzer_eval(other_macro_diag(1) == 1); // expected-warning{{TRUE}}
+  // expected-warning@Inputs/ctu-other.cpp:75{{REACHABLE}}
+  MACRODIAG(); // expected-warning{{REACHABLE}}
 }