From a1c275436ff52e99b90fe8c43cb153fc7ec35716 Mon Sep 17 00:00:00 2001
From: IOBYTE <reif@earthlink.net>
Date: Sat, 15 Dec 2018 01:52:47 -0500
Subject: [PATCH] Fix #8902 (Crash in TemplateSimplifier) (#1521)

---
 lib/templatesimplifier.cpp    |  3 +--
 test/testsimplifytemplate.cpp | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/templatesimplifier.cpp b/lib/templatesimplifier.cpp
index 70d5cce0f..b1c7c9326 100644
--- a/lib/templatesimplifier.cpp
+++ b/lib/templatesimplifier.cpp
@@ -573,7 +573,6 @@ void TemplateSimplifier::getTemplateInstantiations()
                     mTemplateInstantiations.emplace_back(tok2->next(), getScopeName(scopeList), tok2->strAt(1), tok2->tokAt(1));
                 } else if (Token::Match(tok2->next(), "class|struct"))
                     const_cast<Token *>(tok2)->deleteNext();
-
             }
 
             // Add outer template..
@@ -1026,7 +1025,7 @@ void TemplateSimplifier::expandTemplate(
     } else if (copy && isFunction) {
         // check if this is an explicit instantiation
         Token * temp = templateInstantiation.token;
-        while (temp && !Token::Match(temp->previous(), "}|;"))
+        while (temp && !Token::Match(temp->previous(), "}|;|extern"))
             temp = temp->previous();
         if (Token::Match(temp, "template !!<")) {
             // just delete "template"
diff --git a/test/testsimplifytemplate.cpp b/test/testsimplifytemplate.cpp
index 289f98bb6..8a686cad3 100644
--- a/test/testsimplifytemplate.cpp
+++ b/test/testsimplifytemplate.cpp
@@ -122,6 +122,7 @@ private:
         TEST_CASE(template82); // 8603
         TEST_CASE(template83);
         TEST_CASE(template84); // #8880
+        TEST_CASE(template85); // #8902 crash
         TEST_CASE(template_specialization_1);  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         TEST_CASE(template_specialization_2);  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         TEST_CASE(template_enum);  // #6299 Syntax error in complex enum declaration (including template)
@@ -1621,6 +1622,21 @@ private:
         ASSERT_EQUALS(exp, tok(code));
     }
 
+    void template85() { // #8902 - crash
+        const char code[] = "template<typename T>\n"
+                            "struct C\n"
+                            "{\n"
+                            "  template<typename U, typename std::enable_if<(!std::is_fundamental<U>::value)>::type* = nullptr>\n"
+                            "  void foo();\n"
+                            "};\n"
+                            "extern template void C<int>::foo<int, nullptr>();\n"
+                            "template<typename T>\n"
+                            "template<typename U, typename std::enable_if<(!std::is_fundamental<U>::value)>::type>\n"
+                            "void C<T>::foo() {}";
+        // @todo the output is very wrong but we are only worried about the crash for now
+        tok(code);
+    }
+
     void template_specialization_1() {  // #7868 - template specialization template <typename T> struct S<C<T>> {..};
         const char code[] = "template <typename T> struct C {};\n"
                             "template <typename T> struct S {a};\n"