[clang][Interp] Don't add 'in call to' diagnostics for builtin frames

clang/lib/AST/Interp/InterpFrame.cpp

@@ -152,6 +152,13 @@ void print(llvm::raw_ostream &OS, const Pointer &P, ASTContext &Ctx,
 }
 
 void InterpFrame::describe(llvm::raw_ostream &OS) const {
+  // We create frames for builtin functions as well, but we can't reliably
+  // diagnose them. The 'in call to' diagnostics for them add no value to the
+  // user _and_ it doesn't generally work since the argument types don't always
+  // match the function prototype. Just ignore them.
+  if (const auto *F = getFunction(); F && F->isBuiltin())
+    return;
+
   const FunctionDecl *F = getCallee();
   if (const auto *M = dyn_cast<CXXMethodDecl>(F);
       M && M->isInstance() && !isa<CXXConstructorDecl>(F)) {

clang/lib/AST/Interp/State.cpp

@@ -155,7 +155,8 @@ void State::addCallStack(unsigned Limit) {
     SmallString<128> Buffer;
     llvm::raw_svector_ostream Out(Buffer);
     F->describe(Out);
-    addDiag(CallRange.getBegin(), diag::note_constexpr_call_here)
-        << Out.str() << CallRange;
+    if (!Buffer.empty())
+      addDiag(CallRange.getBegin(), diag::note_constexpr_call_here)
+          << Out.str() << CallRange;
   }
 }

clang/test/AST/Interp/builtin-functions.cpp

@@ -24,16 +24,13 @@ namespace strcmp {
   static_assert(__builtin_strcmp("abab", "abab\0banana") == 0, "");
   static_assert(__builtin_strcmp("abab\0banana", "abab\0canada") == 0, "");
   static_assert(__builtin_strcmp(0, "abab") == 0, ""); // both-error {{not an integral constant}} \
-                                                       // both-note {{dereferenced null}} \
-                                                       // expected-note {{in call to}}
+                                                       // both-note {{dereferenced null}}
   static_assert(__builtin_strcmp("abab", 0) == 0, ""); // both-error {{not an integral constant}} \
-                                                       // both-note {{dereferenced null}} \
-                                                       // expected-note {{in call to}}
+                                                       // both-note {{dereferenced null}}
 
   static_assert(__builtin_strcmp(kFoobar, kFoobazfoobar) == -1, "");
   static_assert(__builtin_strcmp(kFoobar, kFoobazfoobar + 6) == 0, ""); // both-error {{not an integral constant}} \
-                                                                        // both-note {{dereferenced one-past-the-end}} \
-                                                                        // expected-note {{in call to}}
+                                                                        // both-note {{dereferenced one-past-the-end}}
 
   /// Used to assert because we're passing a dummy pointer to
   /// __builtin_strcmp() when evaluating the return statement.
@@ -72,14 +69,11 @@ constexpr const char *a = "foo\0quux";
   static_assert(check(c), "");
 
   constexpr int over1 = __builtin_strlen(a + 9); // both-error {{constant expression}} \
-                                                 // both-note {{one-past-the-end}} \
-                                                 // expected-note {{in call to}}
+                                                 // both-note {{one-past-the-end}}
   constexpr int over2 = __builtin_strlen(b + 9); // both-error {{constant expression}} \
-                                                 // both-note {{one-past-the-end}} \
-                                                 // expected-note {{in call to}}
+                                                 // both-note {{one-past-the-end}}
   constexpr int over3 = __builtin_strlen(c + 9); // both-error {{constant expression}} \
-                                                 // both-note {{one-past-the-end}} \
-                                                 // expected-note {{in call to}}
+                                                 // both-note {{one-past-the-end}}
 
   constexpr int under1 = __builtin_strlen(a - 1); // both-error {{constant expression}} \
                                                   // both-note {{cannot refer to element -1}}
@@ -90,8 +84,7 @@ constexpr const char *a = "foo\0quux";
 
   constexpr char d[] = { 'f', 'o', 'o' }; // no nul terminator.
   constexpr int bad = __builtin_strlen(d); // both-error {{constant expression}} \
-                                           // both-note {{one-past-the-end}} \
-                                           // expected-note {{in call to}}
+                                           // both-note {{one-past-the-end}}
 }
 
 namespace nan {
@@ -114,8 +107,7 @@ namespace nan {
   /// FIXME: Current interpreter misses diagnostics.
   constexpr char f2[] = {'0', 'x', 'A', 'E'}; /// No trailing 0 byte.
   constexpr double NaN7 = __builtin_nan(f2); // both-error {{must be initialized by a constant expression}} \
-                                             // expected-note {{read of dereferenced one-past-the-end pointer}} \
-                                             // expected-note {{in call to}}
+                                             // expected-note {{read of dereferenced one-past-the-end pointer}}
   static_assert(!__builtin_issignaling(__builtin_nan("")), "");
   static_assert(__builtin_issignaling(__builtin_nans("")), "");
 }