Fix seg fault passing invalid unicode values to std::string

Problem reported as starting with python-3.13.
Due to error not being cleared before calling Python C APIs.

The alternative could have been to ensure SWIG_AsCharPtrAndSize
never returns with a pending error (not that easy).

Closes #3051

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.3.0 (in progress)
 ===========================
 
+2024-10-20: wsfulton
+            #3051 Fix seg fault passing invalid unicode values when expecting a
+            std::string type - fix for python-3.13.
+
 2024-10-19: olly
 	    [ruby] Documentation comments now use `true` and `false` for bool
 	    parameter default values, instead of `True` and `False` (which are

Examples/test-suite/python/li_std_string_runme.py

@@ -1,9 +1,25 @@
+import sys
 from li_std_string import *
 
 def check(condition):
     if not condition:
         raise RuntimeError
 
+# Bad Unicode input check
+# This check is run first to check that %error_clear is called the first time SWIG_AsPtr_std_string()
+# is called setting the descriptor singleton (by calling SWIG_TypeQuery()).
+# Bug https://github.com/swig/swig/issues/3051.
+exceptionRaised = False
+try:
+    if sys.version_info[0:2] < (3, 0):
+        v = u"./\uDCFC.conf"
+    else:
+        v = "./\uDCFC.conf"
+    test_value(v)
+except TypeError:
+    exceptionRaised = True
+check(exceptionRaised)
+
 # Checking expected use of %typemap(in) std::string {}
 test_value("Fee")
 
@@ -13,9 +29,9 @@ check(test_value("Fi") == "Fi")
 # Verify type-checking for %typemap(in) std::string {}
 exceptionRaised = False
 try:
-  test_value(0)
+    test_value(0)
 except TypeError:
-  exceptionRaised = True
+    exceptionRaised = True
 check(exceptionRaised)
 
 # Checking expected use of %typemap(in) const std::string & {}
@@ -27,9 +43,9 @@ check(test_const_reference("Fum") == "Fum")
 # Verify type-checking for %typemap(in) const std::string & {}
 exceptionRaised = False
 try:
-  test_const_reference(0)
+    test_const_reference(0)
 except TypeError:
-  exceptionRaised = True
+    exceptionRaised = True
 check(exceptionRaised)
 
 #
@@ -40,9 +56,9 @@ check(exceptionRaised)
 
 exceptionRaised = False
 try:
-  test_pointer("foo")
+    test_pointer("foo")
 except TypeError:
-  exceptionRaised = True
+    exceptionRaised = True
 check(exceptionRaised)
 
 result = test_pointer_out()
@@ -50,9 +66,9 @@ check(not isinstance(result, str))
 
 exceptionRaised = False
 try:
-  test_const_pointer("bar")
+    test_const_pointer("bar")
 except TypeError:
-  exceptionRaised = True
+    exceptionRaised = True
 check(exceptionRaised)
 
 result = test_const_pointer_out()
@@ -60,9 +76,9 @@ check(not isinstance(result, str))
 
 exceptionRaised = False
 try:
-  test_reference("foo")
+    test_reference("foo")
 except TypeError:
-  exceptionRaised = True
+    exceptionRaised = True
 check(exceptionRaised)
 
 result = test_reference_out()
@@ -72,50 +88,50 @@ check(not isinstance(result, str))
 # Member Strings
 myStructure = Structure()
 if myStructure.MemberString2 != "member string 2":
-  raise RuntimeError
+    raise RuntimeError
 s = "Hello"
 myStructure.MemberString2 = s
 if myStructure.MemberString2 != s:
-  raise RuntimeError
+    raise RuntimeError
 if myStructure.ConstMemberString != "const member string":
-  raise RuntimeError 
+    raise RuntimeError 
 
 
 if cvar.Structure_StaticMemberString2 != "static member string 2":
-  raise RuntimeError
+    raise RuntimeError
 cvar.Structure_StaticMemberString2 = s
 if cvar.Structure_StaticMemberString2 != s:
-  raise RuntimeError
+    raise RuntimeError
 if Structure.ConstStaticMemberString != "const static member string":
-  raise RuntimeError
+    raise RuntimeError
 
 
 if test_reference_input("hello") != "hello":
-  raise RuntimeError
+    raise RuntimeError
 s = test_reference_inout("hello")
 if s != "hellohello":
-  raise RuntimeError
+    raise RuntimeError
 if test_reference_output() != "output":
-  raise RuntimeError
+    raise RuntimeError
 
 
 if stdstring_empty() != "":
-  raise RuntimeError
+    raise RuntimeError
 
 if c_empty() != "":
-  raise RuntimeError
+    raise RuntimeError
 
 
 if c_null() != None:
-  raise RuntimeError
+    raise RuntimeError
 
 
 if get_null(c_null()) != None:
-  raise RuntimeError
+    raise RuntimeError
 
 
 if get_null(c_empty()) != "non-null":
-  raise RuntimeError
+    raise RuntimeError
 
 if get_null(stdstring_empty()) != "non-null":
-  raise RuntimeError
+    raise RuntimeError

Lib/python/pytypemaps.swg

@@ -57,6 +57,9 @@
 /* raise */
 #define SWIG_Raise(obj, type, desc)     SWIG_Python_Raise(obj, type, desc)
 
+/* clear errors */
+#define %error_clear PyErr_Clear()
+
 /* Include the unified typemap library */
 %include <typemaps/swigtypemaps.swg>
 

Lib/typemaps/std_strings.swg

@@ -17,12 +17,8 @@ SWIG_AsPtr_dec(String)(SWIG_Object obj, String **val)
       return SWIG_OLDOBJ;
     }
   } else {
-    static int init = 0;
-    static swig_type_info* descriptor = 0;
-    if (!init) {
-      descriptor = SWIG_TypeQuery(#String " *");
-      init = 1;
-    }
+    %error_clear;
+    static swig_type_info *descriptor = SWIG_TypeQuery(#String " *");
     if (descriptor) {
       String *vptr;
       int res = SWIG_ConvertPtr(obj, (void**)&vptr, descriptor, 0);

Lib/typemaps/swigtypemaps.swg

@@ -121,6 +121,12 @@
 #endif
 #endif
 
+/*==== clear errors ====*/
+
+#ifndef %error_clear
+#define %error_clear
+#endif
+
 /*==== director output exception ====*/
 
 #if defined(SWIG_DIRECTOR_TYPEMAPS)