Added model for gettext variants.

Author: bdrodes

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

@@ -3,6 +3,7 @@ private import implementations.Deallocation
 private import implementations.Fread
 private import implementations.Getenv
 private import implementations.Gets
+private import implementations.GetText
 private import implementations.IdentityFunction
 private import implementations.Inet
 private import implementations.Iterator

cpp/ql/lib/semmle/code/cpp/models/implementations/GetText.qll

@@ -0,0 +1,35 @@
+import semmle.code.cpp.models.interfaces.DataFlow
+
+/**
+ * Returns the transated text index for a given gettext function `f`
+ */
+private int getTextArg(Function f) {
+  // basic variations of gettext
+  f.hasGlobalOrStdName("gettext") and result = 0
+  or
+  f.hasGlobalOrStdName("dgettext") and result = 1
+  or
+  f.hasGlobalOrStdName("dcgettext") and result = 1
+  or
+  // plural variations of gettext that take one format string for singular and another for plural form
+  f.hasGlobalOrStdName("ngettext") and
+  (result = 0 or result = 1)
+  or
+  f.hasGlobalOrStdName("dngettext") and
+  (result = 1 or result = 2)
+  or
+  f.hasGlobalOrStdName("dcngettext") and
+  (result = 1 or result = 2)
+}
+
+class GetTextFunction extends DataFlowFunction {
+  int argInd;
+
+  GetTextFunction() { argInd = getTextArg(this) }
+
+  override predicate hasDataFlow(FunctionInput input, FunctionOutput output) {
+    input.isParameter(argInd) and output.isReturnValue()
+    or
+    input.isParameterDeref(argInd) and output.isReturnValueDeref()
+  }
+}