Introduce a limit on the depth of the template instantiation backtrace

we will print with each error that occurs during template
instantiation. When the backtrace is longer than that, we will print
N/2 of the innermost backtrace entries and N/2 of the outermost
backtrace entries, then skip the middle entries with a note such as:

  note: suppressed 2 template instantiation contexts; use
  -ftemplate-backtrace-limit=N to change the number of template
  instantiation entries shown

This should eliminate some excessively long backtraces that aren't
providing any value.

llvm-svn: 101882

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 932481f87f6..f9cfd73c7e6 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -240,6 +240,11 @@ static void DiagnosticOptsToArgs(const DiagnosticOptions &Opts,
     Res.push_back("-ferror-limit");
     Res.push_back(llvm::utostr(Opts.ErrorLimit));
   }
+  if (Opts.TemplateBacktraceLimit != 10) {
+    Res.push_back("-ftemplate-backtrace-limit");
+    Res.push_back(llvm::utostr(Opts.TemplateBacktraceLimit));
+  }
+
   if (Opts.TabStop != DiagnosticOptions::DefaultTabStop) {
     Res.push_back("-ftabstop");
     Res.push_back(llvm::utostr(Opts.TabStop));
@@ -857,6 +862,8 @@ static void ParseDiagnosticArgs(DiagnosticOptions &Opts, ArgList &Args,
   Opts.VerifyDiagnostics = Args.hasArg(OPT_verify);
   Opts.BinaryOutput = Args.hasArg(OPT_fdiagnostics_binary);
   Opts.ErrorLimit = getLastArgIntValue(Args, OPT_ferror_limit, 0, Diags);
+  Opts.TemplateBacktraceLimit
+    = getLastArgIntValue(Args, OPT_ftemplate_backtrace_limit, 0, Diags);
   Opts.TabStop = getLastArgIntValue(Args, OPT_ftabstop,
                                     DiagnosticOptions::DefaultTabStop, Diags);
   if (Opts.TabStop == 0 || Opts.TabStop > DiagnosticOptions::MaxTabStop) {