From c52e5792db530f43b1039539359c60d53e560eb3 Mon Sep 17 00:00:00 2001
From: peter klausler <pklausler@nvidia.com>
Date: Fri, 6 Apr 2018 14:20:29 -0700
Subject: [PATCH] [flang] Crash more gracefully when files include themselves.

Original-commit: flang-compiler/f18@6da9ec422824b7e86b10bb368fedd5b734063ce8
Reviewed-on: https://github.com/flang-compiler/f18/pull/48
Tree-same-pre-rewrite: false
---
 flang/lib/parser/prescan.cc | 8 ++++++++
 flang/lib/parser/prescan.h  | 1 +
 2 files changed, 9 insertions(+)

diff --git a/flang/lib/parser/prescan.cc b/flang/lib/parser/prescan.cc
index b3132e1..0f9b154 100644
--- a/flang/lib/parser/prescan.cc
+++ b/flang/lib/parser/prescan.cc
@@ -14,6 +14,8 @@
 namespace Fortran {
 namespace parser {
 
+static constexpr int maxPrescannerNesting{100};
+
 Prescanner::Prescanner(
     Messages &messages, CookedSource &cooked, Preprocessor &preprocessor)
   : messages_{messages}, cooked_{cooked}, preprocessor_{preprocessor} {}
@@ -26,6 +28,7 @@ Prescanner::Prescanner(const Prescanner &that)
     enableBackslashEscapesInCharLiterals_{
         that.enableBackslashEscapesInCharLiterals_},
     warnOnNonstandardUsage_{that.warnOnNonstandardUsage_},
+    prescannerNesting_{that.prescannerNesting_ + 1},
     compilerDirectiveBloomFilter_{that.compilerDirectiveBloomFilter_},
     compilerDirectiveSentinels_{that.compilerDirectiveSentinels_} {}
 
@@ -53,6 +56,11 @@ void Prescanner::Prescan(ProvenanceRange range) {
   limit_ = start_ + range.size();
   lineStart_ = start_;
   const bool beganInFixedForm{inFixedForm_};
+  if (prescannerNesting_ > maxPrescannerNesting) {
+    Say("too many nested INCLUDE/#include files, possibly circular"_err_en_US,
+        GetProvenance(start_));
+    return;
+  }
   while (lineStart_ < limit_) {
     Statement();
   }
diff --git a/flang/lib/parser/prescan.h b/flang/lib/parser/prescan.h
index 81953c4..d96c013 100644
--- a/flang/lib/parser/prescan.h
+++ b/flang/lib/parser/prescan.h
@@ -156,6 +156,7 @@ private:
   bool enableBackslashEscapesInCharLiterals_{true};
   bool warnOnNonstandardUsage_{false};
   int delimiterNesting_{0};
+  int prescannerNesting_{0};
 
   Provenance startProvenance_;
   const char *start_{nullptr};  // beginning of current source file content
-- 
2.7.4