Revert "C++: change note" and "C++: Exclusion rules for system macros"

This reverts commit a055c86.
This reverts commit 237a7d3.

Author: geoffw0

cpp/change-notes/2021-09-21-jpl24.md

@@ -81,8 +81,8 @@ predicate functionContainsPreprocCode(Function f) {
 }
 
 /**
- * Holds if `e` is completely or partially from a macro invocation `mi`, as
- * opposed to being passed in as an argument.
+ * Holds if `e` is completely or partially from a macro definition, as opposed
+ * to being passed in as an argument.
  *
  * In the following example, the call to `f` is from a macro definition,
  * while `y`, `+`, `1`, and `;` are not. This assumes that no identifier apart
@@ -93,8 +93,8 @@ predicate functionContainsPreprocCode(Function f) {
  *   M(y + 1);
  * ```
  */
-private predicate isFromMacroInvocation(Element e, MacroInvocation mi) {
-  exists(Location eLocation, Location miLocation |
+predicate isFromMacroDefinition(Element e) {
+  exists(MacroInvocation mi, Location eLocation, Location miLocation |
     mi.getAnExpandedElement() = e and
     eLocation = e.getLocation() and
     miLocation = mi.getLocation() and
@@ -109,39 +109,3 @@ private predicate isFromMacroInvocation(Element e, MacroInvocation mi) {
     eLocation.getEndColumn() >= miLocation.getEndColumn()
   )
 }
-
-/**
- * Holds if `e` is completely or partially from a macro definition, as opposed
- * to being passed in as an argument.
- *
- * In the following example, the call to `f` is from a macro definition,
- * while `y`, `+`, `1`, and `;` are not. This assumes that no identifier apart
- * from `M` refers to a macro.
- * ```
- * #define M(x) f(x)
- * ...
- *   M(y + 1);
- * ```
- */
-predicate isFromMacroDefinition(Element e) {
-  isFromMacroInvocation(e, _)
-}
-
-/**
- * Holds if `e` is completely or partially from a _system macro_ definition, as
- * opposed to being passed in as an argument. A system macro is a macro whose
- * definition is outside the source directory of the database.
- * 
- * If the system macro is invoked through a non-system macro, then this
- * predicate does not hold. That's a limitation of how macros are represented
- * in the database.
- *
- * See also `isFromMacroDefinition`.
- */
-predicate isFromSystemMacroDefinition(Element e) {
-  exists(MacroInvocation mi |
-    isFromMacroInvocation(e, mi) and
-    // Has no relative path in the database, meaning it's a system file.
-    not exists(mi.getMacro().getFile().getRelativePath())
-  )
-}

cpp/ql/lib/semmle/code/cpp/commons/Exclusions.qll

@@ -10,7 +10,6 @@
  */
 
 import cpp
-import semmle.code.cpp.commons.Exclusions
 
 class OneLineStmt extends Stmt {
   OneLineStmt() {
@@ -35,8 +34,5 @@ where
       other.onLine(f, line) and toMin = other.getLocation().getStartColumn()
     |
       toMin
-    ) and
-  // Exclude statements that are from invocations of system-header macros.
-  // Example: FD_ISSET from glibc.
-  not isFromSystemMacroDefinition(o)
+    )
 select o, "This line contains " + cnt + " statements; only one is allowed."

cpp/ql/src/JPL_C/LOC-4/Rule 24/MultipleStmtsPerLine.ql

@@ -10,15 +10,11 @@
  */
 
 import cpp
-import semmle.code.cpp.commons.Exclusions
 
 from DeclStmt d
 where
   exists(Variable v1, Variable v2 | v1 = d.getADeclaration() and v2 = d.getADeclaration() |
     v1 != v2 and
     v1.getLocation().getStartLine() = v2.getLocation().getStartLine()
-  ) and
-  // Exclude declarations that are from invocations of system-header macros.
-  // Example: FD_ZERO from glibc.
-  not isFromSystemMacroDefinition(d)
+  )
 select d, "Multiple variable declarations on the same line."