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, 6 insertions, 0 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index d9df471714a..4653551a469 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -1079,6 +1079,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(A->getValue(Args));
   else
     CmdArgs.push_back("19");
+
+  CmdArgs.push_back("-ftemplate-backtrace-limit");
+  if (Arg *A = Args.getLastArg(options::OPT_ftemplate_backtrace_limit_EQ))
+    CmdArgs.push_back(A->getValue(Args));
+  else
+    CmdArgs.push_back("10");
   
   // Pass -fmessage-length=.
   CmdArgs.push_back("-fmessage-length");