make C char* string literals "const" unless specified otherwise

prevent non-const char* string literals from being interned

Cython/Compiler/Code.py

@@ -1180,6 +1180,11 @@ class GlobalState(object):
     def get_interned_identifier(self, text):
         return self.get_py_string_const(text, identifier=True)
 
+    def as_c_string_literal(self, byte_string):
+        value = StringEncoding.split_string_literal(
+            StringEncoding.escape_byte_string(byte_string.byteencode()))
+        return '"%s"' % value
+
     def new_string_const(self, text, byte_string):
         cname = self.new_string_const_cname(byte_string)
         c = StringConst(cname, text, byte_string)
@@ -1313,7 +1318,7 @@ class GlobalState(object):
                 conditional = True
                 decls_writer.putln("#if PY_MAJOR_VERSION %s 3" % (
                     (2 in c.py_versions) and '<' or '>='))
-            decls_writer.putln('static char %s[] = "%s";' % (
+            decls_writer.putln('static const char %s[] = "%s";' % (
                 cname, StringEncoding.split_string_literal(c.escaped_value)))
             if conditional:
                 decls_writer.putln("#endif")
@@ -1639,6 +1644,9 @@ class CCodeWriter(object):
         return self.globalstate.get_py_string_const(
             text, identifier, is_str, unicode_value).cname
 
+    def as_c_string_literal(self, text):
+        return self.globalstate.as_c_string_literal(text)
+
     def get_argument_default_const(self, type):
         return self.globalstate.get_py_const(type).cname
 

Cython/Compiler/ExprNodes.py

@@ -81,21 +81,33 @@ coercion_error_dict = {
                                " This is not portable and requires explicit encoding."),
     (unicode_type, bytes_type): "Cannot convert Unicode string to 'bytes' implicitly, encoding required.",
     (unicode_type, PyrexTypes.c_char_ptr_type): "Unicode objects only support coercion to Py_UNICODE*.",
+    (unicode_type, PyrexTypes.c_const_char_ptr_type): "Unicode objects only support coercion to Py_UNICODE*.",
     (unicode_type, PyrexTypes.c_uchar_ptr_type): "Unicode objects only support coercion to Py_UNICODE*.",
+    (unicode_type, PyrexTypes.c_const_uchar_ptr_type): "Unicode objects only support coercion to Py_UNICODE*.",
     (bytes_type, unicode_type): "Cannot convert 'bytes' object to unicode implicitly, decoding required",
     (bytes_type, str_type): "Cannot convert 'bytes' object to str implicitly. This is not portable to Py3.",
     (bytes_type, basestring_type): ("Cannot convert 'bytes' object to basestring implicitly."
                                     " This is not portable to Py3."),
     (bytes_type, PyrexTypes.c_py_unicode_ptr_type): "Cannot convert 'bytes' object to Py_UNICODE*, use 'unicode'.",
+    (bytes_type, PyrexTypes.c_const_py_unicode_ptr_type): (
+        "Cannot convert 'bytes' object to Py_UNICODE*, use 'unicode'."),
     (basestring_type, bytes_type): "Cannot convert 'basestring' object to bytes implicitly. This is not portable.",
     (str_type, unicode_type): ("str objects do not support coercion to unicode,"
                                " use a unicode string literal instead (u'')"),
     (str_type, bytes_type): "Cannot convert 'str' to 'bytes' implicitly. This is not portable.",
     (str_type, PyrexTypes.c_char_ptr_type): "'str' objects do not support coercion to C types (use 'bytes'?).",
+    (str_type, PyrexTypes.c_const_char_ptr_type): "'str' objects do not support coercion to C types (use 'bytes'?).",
     (str_type, PyrexTypes.c_uchar_ptr_type): "'str' objects do not support coercion to C types (use 'bytes'?).",
+    (str_type, PyrexTypes.c_const_uchar_ptr_type): "'str' objects do not support coercion to C types (use 'bytes'?).",
     (str_type, PyrexTypes.c_py_unicode_ptr_type): "'str' objects do not support coercion to C types (use 'unicode'?).",
+    (str_type, PyrexTypes.c_const_py_unicode_ptr_type): (
+        "'str' objects do not support coercion to C types (use 'unicode'?)."),
     (PyrexTypes.c_char_ptr_type, unicode_type): "Cannot convert 'char*' to unicode implicitly, decoding required",
+    (PyrexTypes.c_const_char_ptr_type, unicode_type): (
+        "Cannot convert 'char*' to unicode implicitly, decoding required"),
     (PyrexTypes.c_uchar_ptr_type, unicode_type): "Cannot convert 'char*' to unicode implicitly, decoding required",
+    (PyrexTypes.c_const_uchar_ptr_type, unicode_type): (
+        "Cannot convert 'char*' to unicode implicitly, decoding required"),
 }
 
 
@@ -103,8 +115,9 @@ def find_coercion_error(type_tuple, default, env):
     err = coercion_error_dict.get(type_tuple)
     if err is None:
         return default
-    elif ((PyrexTypes.c_char_ptr_type in type_tuple or PyrexTypes.c_uchar_ptr_type in type_tuple)
-            and env.directives['c_string_encoding']):
+    elif (env.directives['c_string_encoding'] and
+              any(t in type_tuple for t in (PyrexTypes.c_char_ptr_type, PyrexTypes.c_uchar_ptr_type,
+                                            PyrexTypes.c_const_char_ptr_type, PyrexTypes.c_const_uchar_ptr_type))):
         if type_tuple[1].is_pyobject:
             return default
         elif env.directives['c_string_encoding'] in ('ascii', 'default'):
@@ -1301,20 +1314,20 @@ class BytesNode(ConstNode):
             return CharNode(self.pos, value=self.value,
                             constant_result=ord(self.value))
 
-        node = BytesNode(self.pos, value=self.value,
-                         constant_result=self.constant_result)
+        node = BytesNode(self.pos, value=self.value, constant_result=self.constant_result)
         if dst_type.is_pyobject:
             if dst_type in (py_object_type, Builtin.bytes_type):
                 node.type = Builtin.bytes_type
             else:
                 self.check_for_coercion_error(dst_type, env, fail=True)
                 return node
-        elif dst_type == PyrexTypes.c_char_ptr_type:
+        elif dst_type in (PyrexTypes.c_char_ptr_type, PyrexTypes.c_const_char_ptr_type):
             node.type = dst_type
             return node
-        elif dst_type == PyrexTypes.c_uchar_ptr_type:
-            node.type = PyrexTypes.c_char_ptr_type
-            return CastNode(node, PyrexTypes.c_uchar_ptr_type)
+        elif dst_type in (PyrexTypes.c_uchar_ptr_type, PyrexTypes.c_const_uchar_ptr_type):
+            node.type = (PyrexTypes.c_const_char_ptr_type if dst_type == PyrexTypes.c_const_uchar_ptr_type
+                         else PyrexTypes.c_char_ptr_type)
+            return CastNode(node, dst_type)
         elif dst_type.assignable_from(PyrexTypes.c_char_ptr_type):
             node.type = dst_type
             return node
@@ -1326,9 +1339,15 @@ class BytesNode(ConstNode):
 
     def generate_evaluation_code(self, code):
         if self.type.is_pyobject:
-            self.result_code = code.get_py_string_const(self.value)
+            result = code.get_py_string_const(self.value)
+        elif self.type.is_const:
+            result = code.get_string_const(self.value)
         else:
-            self.result_code = code.get_string_const(self.value)
+            # not const => use plain C string literal and cast to mutable type
+            literal = code.as_c_string_literal(self.value)
+            # C++ may require a cast
+            result = typecast(self.type, PyrexTypes.c_void_ptr_type, literal)
+        self.result_code = result
 
     def get_constant_c_result_code(self):
         return None # FIXME
@@ -4146,7 +4165,7 @@ class SliceIndexNode(ExprNode):
         stop_code = self.stop_code()
         if self.base.type.is_string:
             base_result = self.base.result()
-            if self.base.type != PyrexTypes.c_char_ptr_type:
+            if self.base.type not in (PyrexTypes.c_char_ptr_type, PyrexTypes.c_const_char_ptr_type):
                 base_result = '((const char*)%s)' % base_result
             if self.type is bytearray_type:
                 type_name = 'ByteArray'

Cython/Compiler/Optimize.py

@@ -351,8 +351,8 @@ class IterationTransform(Visitor.EnvTransform):
                     base=ExprNodes.BytesNode(
                         slice_node.pos, value=bytes_value,
                         constant_result=bytes_value,
-                        type=PyrexTypes.c_char_ptr_type).coerce_to(
-                            PyrexTypes.c_uchar_ptr_type, self.current_env()),
+                        type=PyrexTypes.c_const_char_ptr_type).coerce_to(
+                            PyrexTypes.c_const_uchar_ptr_type, self.current_env()),
                     start=None,
                     stop=ExprNodes.IntNode(
                         slice_node.pos, value=str(len(bytes_value)),
@@ -2315,12 +2315,12 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
 
     Pyx_strlen_func_type = PyrexTypes.CFuncType(
         PyrexTypes.c_size_t_type, [
-            PyrexTypes.CFuncTypeArg("bytes", PyrexTypes.c_char_ptr_type, None)
+            PyrexTypes.CFuncTypeArg("bytes", PyrexTypes.c_const_char_ptr_type, None)
         ])
 
     Pyx_Py_UNICODE_strlen_func_type = PyrexTypes.CFuncType(
         PyrexTypes.c_size_t_type, [
-            PyrexTypes.CFuncTypeArg("unicode", PyrexTypes.c_py_unicode_ptr_type, None)
+            PyrexTypes.CFuncTypeArg("unicode", PyrexTypes.c_const_py_unicode_ptr_type, None)
         ])
 
     PyObject_Size_func_type = PyrexTypes.CFuncType(
@@ -3253,8 +3253,8 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
     PyUnicode_AsEncodedString_func_type = PyrexTypes.CFuncType(
         Builtin.bytes_type, [
             PyrexTypes.CFuncTypeArg("obj", Builtin.unicode_type, None),
-            PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_char_ptr_type, None),
-            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_const_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_const_char_ptr_type, None),
             ])
 
     PyUnicode_AsXyzString_func_type = PyrexTypes.CFuncType(
@@ -3321,18 +3321,18 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
 
     PyUnicode_DecodeXyz_func_ptr_type = PyrexTypes.CPtrType(PyrexTypes.CFuncType(
         Builtin.unicode_type, [
-            PyrexTypes.CFuncTypeArg("string", PyrexTypes.c_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("string", PyrexTypes.c_const_char_ptr_type, None),
             PyrexTypes.CFuncTypeArg("size", PyrexTypes.c_py_ssize_t_type, None),
-            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_const_char_ptr_type, None),
         ]))
 
     _decode_c_string_func_type = PyrexTypes.CFuncType(
         Builtin.unicode_type, [
-            PyrexTypes.CFuncTypeArg("string", PyrexTypes.c_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("string", PyrexTypes.c_const_char_ptr_type, None),
             PyrexTypes.CFuncTypeArg("start", PyrexTypes.c_py_ssize_t_type, None),
             PyrexTypes.CFuncTypeArg("stop", PyrexTypes.c_py_ssize_t_type, None),
-            PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_char_ptr_type, None),
-            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_const_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_const_char_ptr_type, None),
             PyrexTypes.CFuncTypeArg("decode_func", PyUnicode_DecodeXyz_func_ptr_type, None),
         ])
 
@@ -3341,8 +3341,8 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
             PyrexTypes.CFuncTypeArg("string", PyrexTypes.py_object_type, None),
             PyrexTypes.CFuncTypeArg("start", PyrexTypes.c_py_ssize_t_type, None),
             PyrexTypes.CFuncTypeArg("stop", PyrexTypes.c_py_ssize_t_type, None),
-            PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_char_ptr_type, None),
-            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_const_char_ptr_type, None),
+            PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_const_char_ptr_type, None),
             PyrexTypes.CFuncTypeArg("decode_func", PyUnicode_DecodeXyz_func_ptr_type, None),
         ])
 
@@ -3436,8 +3436,8 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
                         PyrexTypes.CFuncTypeArg("string", string_type, None),
                         PyrexTypes.CFuncTypeArg("start", PyrexTypes.c_py_ssize_t_type, None),
                         PyrexTypes.CFuncTypeArg("stop", PyrexTypes.c_py_ssize_t_type, None),
-                        PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_char_ptr_type, None),
-                        PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_char_ptr_type, None),
+                        PyrexTypes.CFuncTypeArg("encoding", PyrexTypes.c_const_char_ptr_type, None),
+                        PyrexTypes.CFuncTypeArg("errors", PyrexTypes.c_const_char_ptr_type, None),
                         PyrexTypes.CFuncTypeArg("decode_func", self.PyUnicode_DecodeXyz_func_ptr_type, None),
                     ])
             helper_func_type = self._decode_cpp_string_func_type
@@ -3509,14 +3509,14 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
             encoding = node.value
             node = ExprNodes.BytesNode(
                 node.pos, value=BytesLiteral(encoding.utf8encode()),
-                type=PyrexTypes.c_char_ptr_type)
+                type=PyrexTypes.c_const_char_ptr_type)
         elif isinstance(node, (ExprNodes.StringNode, ExprNodes.BytesNode)):
             encoding = node.value.decode('ISO-8859-1')
             node = ExprNodes.BytesNode(
-                node.pos, value=node.value, type=PyrexTypes.c_char_ptr_type)
+                node.pos, value=node.value, type=PyrexTypes.c_const_char_ptr_type)
         elif node.type is Builtin.bytes_type:
             encoding = None
-            node = node.coerce_to(PyrexTypes.c_char_ptr_type, self.current_env())
+            node = node.coerce_to(PyrexTypes.c_const_char_ptr_type, self.current_env())
         elif node.type.is_string:
             encoding = None
         else:

Cython/Compiler/PyrexTypes.py

@@ -2186,6 +2186,8 @@ class CPointerBaseType(CType):
 
     def __init__(self, base_type):
         self.base_type = base_type
+        if base_type.is_const:
+            base_type = base_type.const_base_type
         for char_type in (c_char_type, c_uchar_type, c_schar_type):
             if base_type.same_as(char_type):
                 self.is_string = 1
@@ -3860,10 +3862,13 @@ c_null_ptr_type =     CNullPtrType(c_void_type)
 c_void_ptr_type =     CPtrType(c_void_type)
 c_void_ptr_ptr_type = CPtrType(c_void_ptr_type)
 c_char_ptr_type =     CPtrType(c_char_type)
+c_const_char_ptr_type = CPtrType(CConstType(c_char_type))
 c_uchar_ptr_type =    CPtrType(c_uchar_type)
+c_const_uchar_ptr_type = CPtrType(CConstType(c_uchar_type))
 c_char_ptr_ptr_type = CPtrType(c_char_ptr_type)
 c_int_ptr_type =      CPtrType(c_int_type)
 c_py_unicode_ptr_type = CPtrType(c_py_unicode_type)
+c_const_py_unicode_ptr_type = CPtrType(CConstType(c_py_unicode_type))
 c_py_ssize_t_ptr_type =  CPtrType(c_py_ssize_t_type)
 c_ssize_t_ptr_type =  CPtrType(c_ssize_t_type)
 c_size_t_ptr_type =  CPtrType(c_size_t_type)
@@ -4064,14 +4069,13 @@ def best_match(args, functions, pos=None, env=None):
 
             assignable = dst_type.assignable_from(src_type)
 
-            # Now take care of normal string literals. So when you call a cdef
+            # Now take care of unprefixed string literals. So when you call a cdef
             # function that takes a char *, the coercion will mean that the
             # type will simply become bytes. We need to do this coercion
             # manually for overloaded and fused functions
             if not assignable and src_type.is_pyobject:
-                if (src_type.is_builtin_type and src_type.name == 'str' and
-                        dst_type.resolve() is c_char_ptr_type):
-                    c_src_type = c_char_ptr_type
+                if src_type.is_builtin_type and src_type.name == 'str' and dst_type.resolve().is_string:
+                    c_src_type = dst_type.resolve()
                 else:
                     c_src_type = src_type.default_coerced_ctype()
 

Cython/Utility/ModuleSetupCode.c

@@ -310,7 +310,7 @@ static CYTHON_INLINE float __PYX_NAN() {
 # endif
 #endif
 
-typedef struct {PyObject **p; char *s; const Py_ssize_t n; const char* encoding;
+typedef struct {PyObject **p; const char *s; const Py_ssize_t n; const char* encoding;
                 const char is_unicode; const char is_str; const char intern; } __Pyx_StringTabEntry; /*proto*/
 
 /////////////// ForceInitThreads.proto ///////////////

tests/run/charptr_decode.pyx

@@ -4,7 +4,7 @@ cimport cython
 ############################################################
 # tests for char* slicing
 
-cdef char* cstring = "abcABCqtp"
+cdef const char* cstring = "abcABCqtp"
 
 @cython.test_assert_path_exists("//PythonCapiCallNode")
 @cython.test_fail_if_path_exists("//AttributeNode")
@@ -37,8 +37,8 @@ def slice_charptr_decode_unknown_encoding():
     >>> print(str(slice_charptr_decode_unknown_encoding()).replace("u'", "'"))
     ('abcABCqtp', 'abcABCqtp', 'abc', 'abcABCqt')
     """
-    cdef char* enc = 'UTF-8'
-    cdef char* error_handling = 'strict'
+    cdef const char* enc = 'UTF-8'
+    cdef const char* error_handling = 'strict'
     return (cstring.decode(enc),
             cstring.decode(enc, error_handling),
             cstring[:3].decode(enc),

tests/run/charptr_len.pyx

 cimport cython
 
 cdef char* s = b"abcdefg"
+cdef const char* cs = b"abcdefg"
 cdef unsigned char* us = b"abcdefg"
+cdef const unsigned char* cus = b"abcdefg"
 cdef bytes pystr =  b"abcdefg"
 
 
@@ -16,6 +18,17 @@ def lentest_char():
     return len(s)
 
 
+@cython.test_assert_path_exists(
+    "//PythonCapiCallNode",
+    )
+def lentest_const_char():
+    """
+    >>> lentest_const_char()
+    7
+    """
+    return len(cs)
+
+
 @cython.test_assert_path_exists(
     "//PythonCapiCallNode",
     )
@@ -63,6 +76,17 @@ def lentest_uchar():
     return len(us)
 
 
+@cython.test_assert_path_exists(
+    "//PythonCapiCallNode",
+    )
+def lentest_const_uchar():
+    """
+    >>> lentest_const_uchar()
+    7
+    """
+    return len(cus)
+
+
 @cython.test_assert_path_exists(
     "//PythonCapiCallNode",
     )

tests/run/posix_test.pyx

@@ -3,18 +3,23 @@ from libc.stdio   cimport *
 from posix.unistd cimport *
 from posix.fcntl  cimport *
 
+
 cdef int noisy_function() except -1:
     cdef int ret = 0
-    ret = printf(b"0123456789\n", 0)
-    assert ret == 11
+    ret = printf(b"012%s6789\n", "345")
+    assert ret == 11  # printf()
+    ret = printf(b"012%d6789\n", 345)
+    assert ret == 11  # printf()
+    ret = printf(b"0123456789\n")
+    assert ret == 11  # printf()
     ret = fflush(stdout)
-    assert ret == 0
-    ret = fprintf(stdout, b"0123456789\n", 0)
-    assert ret == 11
+    assert ret == 0  # fflush()
+    ret = fprintf(stdout, b"012%d6789\n", 345)
+    assert ret == 11  # fprintf()
     ret = fflush(stdout)
-    assert ret == 0
+    assert ret == 0  # fflush()
     ret = write(STDOUT_FILENO, b"0123456789\n", 11)
-    assert ret == 11
+    assert ret == 11  # write()
     return  0
 
 
@@ -40,8 +45,8 @@ def test_silent_stdout():
         ret = close(stdout_save)
         assert ret == 0
 
-cdef class silent_fd:
 
+cdef class silent_fd:
     cdef int fd_save, fd
 
     def __cinit__(self, int fd=-1):
@@ -77,6 +82,7 @@ cdef class silent_fd:
             self.fd_save = -1
         return None
 
+
 def test_silent_stdout_ctxmanager():
     """
     >> test_silent_stdout_ctxmanager()