Fix #12808 FP passedByValue for struct parameter in extern "C" function (#6516)

Author: chrchr-github

lib/tokenize.cpp

@@ -1794,7 +1794,7 @@ void Tokenizer::simplifyTypedefCpp()
                 }
 
                 // check for typedef that can be substituted
-                else if ((tok2->isNameOnly() || (tok2->isName() && (tok2->isExpandedMacro() || tok2->isInline()))) &&
+                else if ((tok2->isNameOnly() || (tok2->isName() && (tok2->isExpandedMacro() || tok2->isInline() || tok2->isExternC()))) &&
                          (Token::simpleMatch(tok2, pattern.c_str(), pattern.size()) ||
                           (inMemberFunc && tok2->str() == typeName->str()))) {
                     // member function class variables don't need qualification

test/testsimplifytypedef.cpp

@@ -219,6 +219,7 @@ class TestSimplifyTypedef : public TestFixture {
         TEST_CASE(simplifyTypedef152);
         TEST_CASE(simplifyTypedef153);
         TEST_CASE(simplifyTypedef154);
+        TEST_CASE(simplifyTypedef155);
 
         TEST_CASE(simplifyTypedefFunction1);
         TEST_CASE(simplifyTypedefFunction2); // ticket #1685
@@ -3614,6 +3615,15 @@ class TestSimplifyTypedef : public TestFixture {
         ASSERT_EQUALS(exp, tok(code));
     }
 
+    void simplifyTypedef155() {
+        const char code[] = "typedef struct S T;\n" // #12808
+                            "typedef struct S { int i; } T;\n"
+                            "extern \"C\" void f(T* t);\n";
+        const char exp[] = "struct S { int i ; } ; "
+                           "void f ( struct S * t ) ;";
+        ASSERT_EQUALS(exp, tok(code));
+    }
+
     void simplifyTypedefFunction1() {
         {
             const char code[] = "typedef void (*my_func)();\n"