Add support for $n special variable expansion in the names of typemap local variables

For example:

  %typemap(in) int MYINT (int $1_temp) { ... }

$1_temp is typically expanded to arg1_temp, arg2_temp etc depending on
which argument the typemap is applied to.

CHANGES.current

@@ -7,6 +7,15 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.4.0 (in progress)
 ===========================
 
+2025-02-19: wsfulton
+            Add support for $n special variable expansion in the names of typemap
+            local variables, such as:
+
+              %typemap(in) int MYINT (int $1_temp) { ... }
+
+            $1_temp is typically expanded to arg1_temp, arg2_temp etc depending on
+            which argument the typemap is applied to.
+
 2025-02-05: wsfulton
             #3075 Regression fix when using -keyword, kwargs or compactdefaultargs
             option. Restore generating a non-const cast to the default value when

Doc/Manual/Typemaps.html

@@ -2090,7 +2090,7 @@ wrap_foo() {
 </pre>
 </div>
 
-<p>There is an exception: if the variable name starts with the <tt>_global_</tt> prefix,
+<p>There are two exceptions: First, if the variable name starts with the <tt>_global_</tt> prefix,
 the argument number is not appended. Such variables can be used throughout the generated
 wrapper function. For example, the above typemap could be rewritten to use <tt>_global_temp</tt>
 instead of <tt>temp</tt> and the generated code would then contain a single <tt>_global_temp</tt> variable
@@ -2105,16 +2105,34 @@ instead of <tt>temp1</tt>, <tt>temp2</tt> and <tt>temp3</tt>:
 </pre>
 </div>
 
+<p>
+The second exception occurs if the local variable name contains the special variable <tt>$n</tt> in the variable name.
+Special variables are covered in the next section, but simply the <tt>$n</tt> special variable is expanded to a unique parameter name, such as <tt>arg1</tt>, <tt>arg2</tt> etc.
+As this special variable already contains a unique name, there is no further need to append an argument number suffix to make the temporary variable name unique.
+So in the example below, <tt>$1_temp</tt> is typically expanded to <tt>arg1_temp</tt>, <tt>arg2_temp</tt> etc depending on which argument the typemap is being used for:
+</p>
+
+<div class="code">
+<pre>
+%typemap(in) std::string * <b>(std::string $1_temp)</b> {
+ ... as above ...
+}
+</pre>
+</div>
 
 <p>
-Some typemaps do not recognize local variables (or they may simply not
-apply). At this time, only typemaps that apply to argument conversion support this (input typemaps such as the "in" typemap).
+<b>Compatibility note: </b> Support for <tt>$n</tt> expansion in typemap local variable names was added in SWIG-4.4.0.
 </p>
 
 <p>
 <b>Note:</b>
 </p>
 
+<p>
+Some typemaps do not recognize local variables (or they may simply not
+apply). At this time, only typemaps that apply to argument conversion support this (input typemaps such as the "in" typemap).
+</p>
+
 <p>
 When declaring a typemap for multiple types, 
 each type must have its own local variable declaration.

Examples/test-suite/csharp/special_variable_macros_runme.cs

@@ -24,5 +24,7 @@ public class runme {
       throw new Exception("test failed");
     if (special_variable_macros.provideStringInt(999) != "1000")
       throw new Exception("test failed");
+    if (special_variable_macros.shortFunction(1, 1) != (200*2 + 200*3))
+      throw new Exception("test failed");
   }
 }

Examples/test-suite/d/special_variable_macros_runme.2.d

@@ -21,4 +21,5 @@ void main() {
   enforce(newName.getStoredName().getName() == "factoryname");
   enforce(makeStringInt("stringint", 999) == "stringint");
   enforce(provideStringInt(999) == "1000");
+  enforce(shortFunction(1, 1) == (200*2 + 200*3));
 }

Examples/test-suite/go/special_variable_macros_runme.go

@@ -31,4 +31,7 @@ func main() {
 	if special_variable_macros.ProvideStringInt(999) != "1000" {
 		panic("test failed")
 	}
+	if special_variable_macros.ShortFunction(1, 1) != (200*2 + 200*3) {
+		panic("test failed");
+	}
 }

Examples/test-suite/java/special_variable_macros_runme.java

@@ -34,5 +34,7 @@ public class special_variable_macros_runme {
       throw new RuntimeException("test failed");
     if (!special_variable_macros.provideStringInt(999).equals("1000"))
       throw new RuntimeException("test failed");
+    if (special_variable_macros.shortFunction((short)1, (short)1) != (200*2 + 200*3))
+      throw new RuntimeException("test failed");
   }
 }

Examples/test-suite/javascript/special_variable_macros_runme.js

@@ -35,3 +35,6 @@ if (special_variable_macros.makeStringInt("stringint", 999) != "stringint") {
 if (special_variable_macros.provideStringInt(999) != "1000") {
     throw new Error("test failed");
 }
+if (special_variable_macros.shortFunction(1, 1) != (200*2 + 200*3)) {
+    throw new Error("test failed");
+}

Examples/test-suite/ocaml/special_variable_macros_runme.ml

@@ -13,4 +13,5 @@ let _ =
   assert (_testJohn '(arg) as int = 123);
   assert (_makeStringInt '("stringint", 999) as string = "stringint");
   assert (_provideStringInt '(999) as string = "1000");
+  assert (_shortFunction '(1, 1) as int = (200*2 + 200*3));
 ;;

Examples/test-suite/python/special_variable_macros_runme.py

@@ -24,3 +24,5 @@ if special_variable_macros.makeStringInt("stringint", 999) != "stringint":
     raise "test failed"
 if special_variable_macros.provideStringInt(999) != "1000":
     raise "test failed"
+if special_variable_macros.shortFunction(1, 1) != (200*2 + 200*3):
+    raise "test failed"

Examples/test-suite/special_variable_macros.i

@@ -306,3 +306,29 @@ std::string provideStringInt(Space::Pair<std::string, int> p) {
   return p.first;
 }
 %}
+
+// Part 3: $typemap() and the 'in' typemap $1 variable substitution in the typemap temporary names list
+%typemap(in) short MYSHORT ($1_type $1_temp_name = 200) %{
+  $1 = $1_temp_name;
+%}
+%typemap(in) short MYSHORT_OUTER {
+  // MYSHORT_OUTER 'in' start
+  int $1_outer = 0;
+  $typemap(in, short MYSHORT, 1=$1_outer)
+  $1 = $1_outer;
+  // MYSHORT_OUTER 'in' end
+}
+%apply short MYSHORT_OUTER { short x, short y }
+%inline %{
+short shortFunction(short x, short y) {
+  return x*2 + y*3;
+}
+%}
+
+%typemap(arginit) int MYINT "$1 = 0;"
+%typemap(in) int MYINT (int $1_temp_name = 300) "" // $1 only appears in temporary list variable name, check this is expanded
+%typemap(argout) int MYINT %{ $1_temp_name *= 2; %} // check that $1_temp_name is available
+%apply int MYINT { int myint1, int myint2 }
+%inline %{
+void intFunction(int myint1, int myint2) {}
+%}

Examples/test-suite/typemap_manyargs.i

@@ -1,21 +1,39 @@
 %module typemap_manyargs
 
-%typemap(in,numinputs=0) (int* a1, int* a2, int* a3, int* a4, int* a5, int* a6, int *a7, int *a8, int *a9, int *a10) (int temp1,int temp2,int temp3,int temp4,int temp5,int temp6,int temp7,int temp8, int temp9, int temp10)
+%typemap(in,numinputs=0) (double* a1, short* a2, int* a3, int* a4, int* a5, int* a6, int *a7, int *a8, int *a9, int *a10) ($*1_ltype temp1,$*2_ltype temp2,int temp3,int temp4,int $5_tmpvar,int temp6,int temp7,int temp8, int temp9, $*10_ltype temp10)
 {
-  $1 = &temp1;      // the code generate for this is arg2 = &temp1;
-  $2 = &temp2;      // the code generate for this is arg3 = &temp2;
+  $1 = &temp1;      // the code generated for this is arg2 = &temp1;
+  $2 = &temp2;      // the code generated for this is arg3 = &temp2;
   $3 = &temp3;      // and so on...
   $4 = &temp4;
-  $5 = &temp5;
+  $5 = &$5_tmpvar;
   $6 = &temp6;
   $7 = &temp7;
   $8 = &temp8;
   $9 = &temp9;
   $10 = &temp10;   // the code generated for this was arg20 = &temp10; and arg20 does not exist.
   int $10_ptr = 0; // Was arg20_ptr
+  $*1_ltype ltype1 = *$1;
+  $*10_ltype ltype10 = *$10;
   (void)$10_ptr;
+  (void)ltype1;
+  (void)ltype10;
 }
 
+// Test $1, $2 temp variable substitutions
 %inline %{
-void my_c_function(char * filename,int* a1, int* a2, int* a3, int* a4, int* a5, int* a6, int *a7, int *a8, int *a9, int *a10) {}
+void my_c_function(char * filename,double* a1, short* a2, int* a3, int* a4, int* a5, int* a6, int *a7, int *a8, int *a9, int *a10) {}
+%}
+
+%typemap(in, numinputs=0) (const char *s, double *d) ($1_type string_temp_$1 = "hello", $*2_ltype double_$2_temp = 0.0, int dummy_$1_$2 = 0)
+{
+  $1 = const_cast<char *>(string_temp_$1);
+  $2 = &double_$2_temp;
+  (void)dummy_$1_$2;
+}
+%typemap(freearg) (const char *s, double *d) ""
+
+void my_funk(const char *s, double *d, int i, const char *s, double *d) {}
+%{
+void my_funk(const char *s1, double *d1, int i, const char *s2, double *d2) {}
 %}

Source/Swig/typemap.c

@@ -869,16 +869,35 @@ static Hash *typemap_search_multi(const_String_or_char_ptr tmap_method, ParmList
 }
 
 
-static void replace_local_types(ParmList *p, const String *name, const String *rep) {
-  SwigType *t;
+static int replace_with_override(String *src, const DOHString_or_char *token, const DOHString_or_char *replace, int flags, Hash *override_vars) {
+  String *override_replace = override_vars ? Getattr(override_vars, token) : NULL;
+  if (override_replace)
+    return Replace(src, token, override_replace, flags);
+  return Replace(src, token, replace, flags);
+}
+
+static void replace_local_types(ParmList *p, const String *name, const String *replace) {
   while (p) {
-    t = Getattr(p, "type");
-    Replace(t, name, rep, DOH_REPLACE_ANY);
+    SwigType *t = Getattr(p, "type");
+    Replace(t, name, replace, DOH_REPLACE_ANY);
     p = nextSibling(p);
   }
 }
 
-static int check_locals(ParmList *p, const char *s) {
+static void replace_local_names(ParmList *p, const String *name, const String *replace, Hash *override_vars) {
+  while (p) {
+    int replaced = 0;
+    SwigType *n = Getattr(p, "name");
+    SwigType *origname = Copy(n);
+    replaced = replace_with_override(n, name, replace, DOH_REPLACE_NUMBER_END, override_vars);
+    if (replaced > 0 && !Getattr(p, "origname"))
+      Setattr(p, "origname", origname);
+    Delete(origname);
+    p = nextSibling(p);
+  }
+}
+
+static int check_locals_type(ParmList *p, const char *s) {
   while (p) {
     char *c = GetChar(p, "type");
     if (strstr(c, s))
@@ -888,13 +907,6 @@ static int check_locals(ParmList *p, const char *s) {
   return 0;
 }
 
-static int replace_with_override(String *src, const DOHString_or_char *token, const DOHString_or_char *rep, int flags, Hash *override_vars) {
-  String *override_replace = override_vars ? Getattr(override_vars, token) : NULL;
-  if (override_replace)
-    return Replace(src, token, override_replace, flags);
-  return Replace(src, token, rep, flags);
-}
-
 /* -----------------------------------------------------------------------------
  * typemap_replace_vars()
  *
@@ -917,15 +929,15 @@ static int typemap_replace_vars(String *s, ParmList *locals, SwigType *type, Swi
   if (!pname)
     pname = lname;
   {
-    Parm *p;
-    int rep = 0;
-    p = locals;
+    int replace = 0;
+    Parm *p = locals;
     while (p) {
-      if (Strchr(Getattr(p, "type"), '$'))
-	rep = 1;
+      String *pname = Getattr(p, "name");
+      if (Strchr(Getattr(p, "type"), '$') || (pname && Strchr(pname, '$')))
+	replace = 1;
       p = nextSibling(p);
     }
-    if (!rep)
+    if (!replace)
       locals = 0;
   }
 
@@ -983,7 +995,7 @@ static int typemap_replace_vars(String *s, ParmList *locals, SwigType *type, Swi
 
     sc = Char(s);
 
-    if (strstr(sc, "type") || check_locals(locals, "type")) {
+    if (strstr(sc, "type") || check_locals_type(locals, "type")) {
       /* Given type : $type */
       ts = SwigType_str(type, 0);
       if (index == 1) {
@@ -996,7 +1008,7 @@ static int typemap_replace_vars(String *s, ParmList *locals, SwigType *type, Swi
       Delete(ts);
       sc = Char(s);
     }
-    if (strstr(sc, "ltype") || check_locals(locals, "ltype")) {
+    if (strstr(sc, "ltype") || check_locals_type(locals, "ltype")) {
       /* Local type:  $ltype */
       ltype = SwigType_ltype(type);
       ts = SwigType_str(ltype, 0);
@@ -1190,6 +1202,8 @@ static int typemap_replace_vars(String *s, ParmList *locals, SwigType *type, Swi
   /* Replace the bare $n variable */
   sprintf(var, "$%d", index);
   bare_substitution_count = replace_with_override(s, var, lname, DOH_REPLACE_NUMBER_END, override_vars);
+  replace_local_names(locals, var, lname, override_vars);
+
   Delete(ftype);
   return bare_substitution_count;
 }
@@ -1227,7 +1241,7 @@ static void typemap_locals(String *s, ParmList *l, Wrapper *f, int argnum) {
 	/* If the user gave us $type as the name of the local variable, we'll use
 	   the passed datatype instead */
 
-	if ((argnum >= 0) && (!isglobal)) {
+	if ((argnum >= 0) && !isglobal && !Getattr(p, "origname")) {
 	  Printf(str, "%s%d", pn, argnum);
 	} else {
 	  Append(str, pn);