From 17bb00d378aea9ea7f7f27618bd736f2c47e3de2 Mon Sep 17 00:00:00 2001
From: Rhys <rimmington@gmail.com>
Date: Fri, 30 Jun 2017 14:14:50 +1000
Subject: [PATCH] Clearer error message when regex exceeds space limit

---
 src/libexpr/primops.cc | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 99ffddaeb..f240e795e 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1734,8 +1734,13 @@ static void prim_match(EvalState & state, const Pos & pos, Value * * args, Value
                 mkString(*(v.listElems()[i] = state.allocValue()), match[i + 1].str().c_str());
         }
 
-    } catch (std::regex_error &) {
-        throw EvalError("invalid regular expression ‘%s’, at %s", re, pos);
+    } catch (std::regex_error &e) {
+        if (e.code() == std::regex_constants::error_space) {
+          // limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
+          throw EvalError("memory limit exceeded by regular expression ‘%s’, at %s", re, pos);
+        } else {
+          throw EvalError("invalid regular expression ‘%s’, at %s", re, pos);
+        }
     }
 }