CPP: Split Strdup model into it's own class and file.

Author: geoffw0

cpp/ql/src/semmle/code/cpp/models/Models.qll

@@ -9,5 +9,6 @@ private import implementations.Printf
 private import implementations.Pure
 private import implementations.Strcat
 private import implementations.Strcpy
+private import implementations.Strdup
 private import implementations.Strftime
 private import implementations.Swap

cpp/ql/src/semmle/code/cpp/models/implementations/Allocation.qll

@@ -173,32 +173,14 @@ class ReallocAllocationFunction extends AllocationFunction {
 }
 
 /**
- * An allocation function (such as `strdup`) that has no explicit argument for
+ * A miscellaneous allocation function that has no explicit argument for
  * the size of the allocation.
  */
-class StrdupAllocationFunction extends AllocationFunction {
-  StrdupAllocationFunction() {
+class SizelessAllocationFunction extends AllocationFunction {
+  SizelessAllocationFunction() {
     exists(string name |
-      hasGlobalOrStdName(name) and
-      (
-        // strdup(str)
-        name = "strdup"
-        or
-        // wcsdup(str)
-        name = "wcsdup"
-      )
-      or
       hasGlobalName(name) and
       (
-        // _strdup(str)
-        name = "_strdup"
-        or
-        // _wcsdup(str)
-        name = "_wcsdup"
-        or
-        // _mbsdup(str)
-        name = "_mbsdup"
-        or
         // ExAllocateFromLookasideListEx(list)
         name = "ExAllocateFromLookasideListEx"
         or

cpp/ql/src/semmle/code/cpp/models/implementations/Strdup.qll

@@ -0,0 +1,31 @@
+import semmle.code.cpp.models.interfaces.Allocation
+
+/**
+ * A `strdup` style allocation function.
+ */
+class StrdupFunction extends AllocationFunction {
+  StrdupFunction() {
+    exists(string name |
+      hasGlobalOrStdName(name) and
+      (
+        // strdup(str)
+        name = "strdup"
+        or
+        // wcsdup(str)
+        name = "wcsdup"
+      )
+      or
+      hasGlobalName(name) and
+      (
+        // _strdup(str)
+        name = "_strdup"
+        or
+        // _wcsdup(str)
+        name = "_wcsdup"
+        or
+        // _mbsdup(str)
+        name = "_mbsdup"
+      )
+    )
+  }
+}