bpo-36876: Make some static string literal arrays constant. #15760

ericsnowcurrently · 2019-09-09T11:30:32Z

This gives us guarantees about immutability.

https://bugs.python.org/issue36876

pganssle

Looks good overall, a few formatting nits around whitespace I found.

Modules/_datetimemodule.c

Modules/_decimal/_decimal.c

pganssle · 2019-09-09T12:31:29Z

Modules/_decimal/_decimal.c

@@ -3735,7 +3735,7 @@ dec_##MPDFUNC(PyObject *self, PyObject *args, PyObject *kwds)  \
 static PyObject *                                                \
 dec_##MPDFUNC(PyObject *self, PyObject *args, PyObject *kwds)    \
 {                                                                \
-    static char *kwlist[] = {"other", "context", NULL};          \
+    static const char *kwlist[] = {"other", "context", NULL};          \


Few other alignment issues like the ones above - probably best to align the newline escapes as above.

bedevere-bot · 2019-09-09T12:31:53Z

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

Modules/_multiprocessing/semaphore.c

pganssle

Here are all the alignment issues I found. Hopefully the "suggestions" are the right number of spaces.

pganssle · 2019-09-09T12:33:49Z

Modules/mmapmodule.c

@@ -1278,7 +1278,7 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
    HANDLE fh = 0;
    int access = (access_mode)ACCESS_DEFAULT;
    DWORD flProtect, dwDesiredAccess;
-    static char *keywords[] = { "fileno", "length",
+    static const char *keywords[] = { "fileno", "length",


Next two lines are also misaligned.

pganssle · 2019-09-09T12:34:50Z

Modules/posixmodule.c

@@ -8976,7 +8976,7 @@ posix_sendfile(PyObject *self, PyObject *args, PyObject *kwdict)
    struct sf_hdtr sf;
    int flags = 0;
    /* Beware that "in" clashes with Python's own "in" operator keyword */
-    static char *keywords[] = {"out", "in",
+    static const char *keywords[] = {"out", "in",
                                "offset", "count",


Alignment here again.

pganssle · 2019-09-09T12:34:57Z

Modules/posixmodule.c

@@ -9092,7 +9092,7 @@ posix_sendfile(PyObject *self, PyObject *args, PyObject *kwdict)
 #else
    Py_ssize_t count;
    PyObject *offobj;
-    static char *keywords[] = {"out", "in",
+    static const char *keywords[] = {"out", "in",


Alignment again.

Modules/selectmodule.c

pganssle · 2019-09-09T12:35:55Z

Python/_warnings.c

@@ -1024,7 +1024,7 @@ get_source_line(PyObject *module_globals, int lineno)
 static PyObject *
 warnings_warn_explicit(PyObject *self, PyObject *args, PyObject *kwds)
 {
-    static char *kwd_list[] = {"message", "category", "filename", "lineno",
+    static const char *kwd_list[] = {"message", "category", "filename", "lineno",
                                "module", "registry", "module_globals",


Alignment here again.

serhiy-storchaka · 2019-09-10T06:22:12Z

Changing char *kwlist[] to const char *kwlist[] is incompatible change, because PyArg_ParseTupleAndKeywords() takes char ** which is not compatible with const char **. The compiler should raise warnings or even errors about this. If not this this change would be made years ago.

It is possible to change the API, but it is long a complex process. It is a separate issue.

Adding consts in Python/Python-ast.c may be good, but this file is generated. You should modify the generating script.

serhiy-storchaka · 2019-09-10T07:34:04Z

Note also that you can add two consts in static char *something[]: static const char * const something[]. One for C-strings, and other for an array.

See #15824 for changes in Python/Python-ast.c.

Co-Authored-By: Paul Ganssle <p.ganssle@gmail.com>

ericsnowcurrently · 2019-09-10T15:46:10Z

Hmm, this won't work out.

georgthegreat · 2021-02-24T10:52:19Z

At the time there is a bunch of forgotten const / const_cast / (char**) c-style casts everywhere in PyArg_ParseTupleAndKeywords invocations.

The list includes the following pip packages (but definitely not limited to):

Is there any way to continue working on the issue?

georgthegreat · 2021-02-25T11:36:20Z

@serhiy-storchaka, could you, please, elaborate on

It is possible to change the API, but it is long a complex process. It is a separate issue.)

At the time the lack of const causes problems i. e. when compiling in MSVC standard conformance mode (which is default for /std:c++latest / /std:c++20).

ericsnowcurrently added 2 commits September 9, 2019 12:24

Fix all PyArg_ParseTupleAndKeywords calls.

5b20d3d

Use "static const" in Python-ast.c.

dd1c235

ericsnowcurrently added the skip news label Sep 9, 2019

ericsnowcurrently requested review from 1st1, abalkin, berkerpeksag, pganssle, rhettinger and skrah as code owners September 9, 2019 11:30

the-knights-who-say-ni added the CLA signed label Sep 9, 2019

bedevere-bot added the awaiting core review label Sep 9, 2019

1st1 approved these changes Sep 9, 2019

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bedevere-bot added awaiting merge and removed awaiting core review labels Sep 9, 2019

pganssle requested changes Sep 9, 2019

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bedevere-bot removed the awaiting merge label Sep 9, 2019

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pganssle reviewed Sep 9, 2019

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Modules/_multiprocessing/semaphore.c Outdated Show resolved Hide resolved

pganssle requested changes Sep 9, 2019

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ericsnowcurrently and others added 5 commits September 10, 2019 16:21

Update Modules/_datetimemodule.c

bc86eab

Co-Authored-By: Paul Ganssle <p.ganssle@gmail.com>

Update Modules/_decimal/_decimal.c

83950ce

Co-Authored-By: Paul Ganssle <p.ganssle@gmail.com>

Update Modules/_decimal/_decimal.c

78da6ca

Co-Authored-By: Paul Ganssle <p.ganssle@gmail.com>

Update Modules/_multiprocessing/semaphore.c

2ea64ea

Co-Authored-By: Paul Ganssle <p.ganssle@gmail.com>

Update Modules/selectmodule.c

4bce0ff

Co-Authored-By: Paul Ganssle <p.ganssle@gmail.com>

ericsnowcurrently closed this Sep 10, 2019

georgthegreat mentioned this pull request Feb 25, 2021

Fix some constness / char literal issues being found by MSVC standard conforming mode protocolbuffers/protobuf#8344

Merged

ericsnowcurrently mentioned this pull request Apr 10, 2022

[subinterpreters] Global C variables are a problem #81057

Closed

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bpo-36876: Make some static string literal arrays constant. #15760

bpo-36876: Make some static string literal arrays constant. #15760

ericsnowcurrently commented Sep 9, 2019 •

edited by bedevere-bot

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bpo-36876: Make some static string literal arrays constant. #15760

bpo-36876: Make some static string literal arrays constant. #15760

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