Fix macro backtrace printing.

Sometimes, a macro that expands to another macro name will not be printed in
the macro backtrace.  This patch finds the missed macro expansions and prints
them.  Fixes PR16799

llvm-svn: 246237

2 files changed, 64 insertions, 8 deletions

diff --git a/clang/lib/Frontend/DiagnosticRenderer.cpp b/clang/lib/Frontend/DiagnosticRenderer.cpp
index 393d379048c..0c94083051d 100644
--- a/clang/lib/Frontend/DiagnosticRenderer.cpp
+++ b/clang/lib/Frontend/DiagnosticRenderer.cpp
@@ -399,13 +399,7 @@ void DiagnosticRenderer::emitSingleMacroExpansion(
     const SourceManager &SM) {
   // Find the spelling location for the macro definition. We must use the
   // spelling location here to avoid emitting a macro backtrace for the note.
-  SourceLocation SpellingLoc = Loc;
-
-  // If this is the expansion of a macro argument, point the caret at the
-  // use of the argument in the definition of the macro, not the expansion.
-  if (SM.isMacroArgExpansion(Loc))
-    SpellingLoc = SM.getImmediateExpansionRange(Loc).first;
-  SpellingLoc = SM.getSpellingLoc(SpellingLoc);
+  SourceLocation SpellingLoc = SM.getSpellingLoc(Loc);
 
   // Map the ranges into the FileID of the diagnostic location.
   SmallVector<CharSourceRange, 4> SpellingRanges;
@@ -477,11 +471,23 @@ void DiagnosticRenderer::emitMacroExpansions(SourceLocation Loc,
   SmallVector<SourceLocation, 8> LocationStack;
   unsigned IgnoredEnd = 0;
   while (Loc.isMacroID()) {
-    LocationStack.push_back(Loc);
+    // If this is the expansion of a macro argument, point the caret at the
+    // use of the argument in the definition of the macro, not the expansion.
+    if (SM.isMacroArgExpansion(Loc))
+      LocationStack.push_back(SM.getImmediateExpansionRange(Loc).first);
+    else
+      LocationStack.push_back(Loc);
+
     if (checkRangesForMacroArgExpansion(Loc, Ranges, SM))
       IgnoredEnd = LocationStack.size();
 
     Loc = SM.getImmediateMacroCallerLoc(Loc);
+
+    // Once the location no longer points into a macro, try stepping through
+    // the last found location.  This sometimes produces additional useful
+    // backtraces.
+    if (Loc.isFileID())
+      Loc = SM.getImmediateMacroCallerLoc(LocationStack.back());
     assert(!Loc.isInvalid() && "must have a valid source location here");
   }
 
diff --git a/clang/test/Misc/diag-macro-backtrace2.c b/clang/test/Misc/diag-macro-backtrace2.c
new file mode 100644
index 00000000000..b5be0ae2fef
--- /dev/null
+++ b/clang/test/Misc/diag-macro-backtrace2.c
@@ -0,0 +1,50 @@
+// RUN: not %clang -cc1 -fsyntax-only %s 2>&1 | FileCheck %s
+
+#define a b
+#define b c
+#define c(x) d(x)
+#define d(x) x*1
+
+#define e f
+#define f g
+#define g(x) h(x)
+#define h(x) x
+
+void PR16799() {
+  const char str[] = "string";
+  a(str);
+  // CHECK: :15:3: error: invalid operands to binary expression
+  // CHECK:       ('const char *' and 'int')
+  // CHECK:   a(str);
+  // CHECK:   ^ ~~~
+  // CHECK: :3:11: note: expanded from macro 'a'
+  // CHECK: #define a b
+  // CHECK:           ^
+  // CHECK: :4:11: note: expanded from macro 'b'
+  // CHECK: #define b c
+  // CHECK:           ^
+  // CHECK: :5:14: note: expanded from macro 'c'
+  // CHECK: #define c(x) d(x)
+  // CHECK:              ^~~~
+  // CHECK: :6:15: note: expanded from macro 'd'
+  // CHECK: #define d(x) x*1
+  // CHECK:               ^~
+
+  e(str);
+  // CHECK: :33:5: warning: expression result unused
+  // CHECK:   e(str);
+  // CHECK:     ^~~
+  // CHECK: :8:11: note: expanded from macro 'e'
+  // CHECK: #define e f
+  // CHECK:           ^
+  // CHECK: :9:11: note: expanded from macro 'f'
+  // CHECK: #define f g
+  // CHECK:           ^
+  // CHECK: :10:16: note: expanded from macro 'g'
+  // CHECK: #define g(x) h(x)
+  // CHECK:                ^
+  // CHECK: :11:14: note: expanded from macro 'h'
+  // CHECK: #define h(x) x
+  // CHECK:              ^
+}
+// CHECK: 1 warning and 1 error generated.