RULE-8-7: Require the reference to exist in the same TU

The translation unit of the definition needs to be the same as the
translation unit of the reference, otherwise it is not eligible
for internal linkage.

Author: lcartey

c/misra/src/rules/RULE-8-7/ShouldNotBeDefinedWithExternalLinkage.ql

@@ -51,6 +51,8 @@ where
   not exists(TranslationUnit t2 |
     isReferencedInTranslationUnit(e, _, t2) and
     not t1 = t2
-  )
+  ) and
+  // Definition is also in the same translation unit
+  e.getDefinition().getFile() = t1.getAUserFile()
 select e, "Declaration with external linkage is accessed in only one translation unit $@.", a1,
   a1.toString()

c/misra/test/rules/RULE-8-7/ShouldNotBeDefinedWithExternalLinkage.expected

@@ -1,3 +1,3 @@
-| test.c:3:5:3:6 | i1 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:10:3:10:4 | i1 | i1 |
-| test.c:4:5:4:6 | i2 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:11:3:11:4 | i2 | i2 |
-| test.c:6:6:6:7 | f2 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:13:3:13:4 | call to f2 | call to f2 |
+| test.c:3:5:3:6 | i1 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:11:3:11:4 | i1 | i1 |
+| test.c:4:5:4:6 | i2 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:12:3:12:4 | i2 | i2 |
+| test.c:6:6:6:7 | f2 | Declaration with external linkage is accessed in only one translation unit $@. | test.c:14:3:14:4 | call to f2 | call to f2 |

c/misra/test/rules/RULE-8-7/test.c

@@ -5,6 +5,7 @@ int i2;              // NON_COMPLIANT - accessed one translation unit
 void f1() {}         // Definition
 void f2() {}         // Definition
 static void f3() {}; // COMPLIANT - internal linkage
+void f4() {}         // Definition
 void f() {
   i = 0;
   i1 = 0;

c/misra/test/rules/RULE-8-7/test.h

@@ -1,4 +1,5 @@
 extern int i;     // COMPLIANT - accessed multiple translation units
 extern int i1;    // NON_COMPLIANT - accessed one translation unit
 extern void f1(); // COMPLIANT  - accessed multiple translation units
-extern void f2(); // NON_COMPLIANT - accessed one translation unit
+extern void f2(); // NON_COMPLIANT - accessed one translation unit
+extern void f4(); // COMPLIANT - accessed across translation units

c/misra/test/rules/RULE-8-7/test1.c

@@ -2,4 +2,5 @@
 void f() {
   i = 0;
   f1();
+  f4();
 }