gh-126937: ctypes: fix TypeError when a field's size is >65535 bytes#126938

Melissa0x1f992 · 2024-11-17T21:30:29Z

Used the bit_size_obj as seems to be intended, based on its usage in Lib/ctypes/_layout.py

Tested the change locally informally. Didn't write any tests.

Issue: Struct fields with size > 65535 bytes throw TypeError #126937

Fix rejection when non-bitfield fields are larger than 2^16 bytes

ghost · 2024-11-17T21:30:32Z

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bedevere-app · 2024-11-17T21:30:33Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

Melissa0x1f992 · 2024-11-17T21:38:43Z

Need some help understanding the lint error on this

Modules/_ctypes/cfield.c

terryjreedy · 2024-11-17T23:31:26Z

By somewhat random clicking of the search box and the test stage line, I got the full log. There were 6 spaces after the final \n, thus trailing spaces failed. (Note that running patchcheck as suggested somewhere would have fixed this.)

I asked to rerun just the one test, but the edit triggered all.

terryjreedy · 2024-11-17T23:36:13Z

I can't review the actual change. It might help someone else if you could connect the change to the change in 3.14 that caused the regression. To find the latter, I would first run git blame on cfield.c

picnixz · 2024-11-18T07:34:11Z

cc @encukou

Use bitsize param

Melissa0x1f992 · 2024-11-18T13:53:30Z

Added a test. It doesn't have any assertions bc the failure case is an error getting raised. Not sure if this is the appropriate way to add such a test.

Reduce test field size to (2^31 - 1) to support 32 bit systems

.pre-commit-config.yaml

Melissa0x1f992 · 2024-11-18T15:43:23Z

For the Win32, I don't have that setup. Could I get some help determining what field size should pass the < (1ULL << (8*sizeof(Py_ssize_t)-1)) / 8) test on Win32? Am I off by one? I don't want to commit (2^31 - 1 - 1) unless there's a good reason to consider that one byte smaller the limit for Win32.

Melissa0x1f992 · 2024-11-18T15:44:49Z

Is there a way for the test to set up different field sizes based on the current platform, and is that desirable? I'd like to test the actual max size, regardless of platform, rather than the smallest of the different platform maxes.

ZeroIntensity

Some initial comments :)

ZeroIntensity · 2024-11-18T15:58:52Z

Misc/NEWS.d/next/Core_and_Builtins/2024-11-17-21-35-55.gh-issue-126937.qluVM0.rst

@@ -0,0 +1 @@
+Fixed TypeError when a Structure's field's size is >65535 bytes


Suggested change
Fixed TypeError when a Structure's field's size is >65535 bytes
Fix :exc:`TypeError` when a :class:`ctypes.Structure` has a field size that doesn't fit into an unsigned 16-bit integer.

ZeroIntensity · 2024-11-18T15:59:14Z

Modules/_ctypes/cfield.c

- Py_ssize_t bit_size = NUM_BITS(size);
- if (bit_size){
+ if (bit_size_obj != Py_None){
+


No need for a newline
Suggested change

ZeroIntensity · 2024-11-18T16:00:23Z

Modules/_ctypes/cfield.c

+ Py_ssize_t bit_size;
+
+ if (PyLong_Check(bit_size_obj)){
+ bit_size = PyLong_AsSsize_t(bit_size_obj);


PyLong_AsSsize_t can fail, you need to check for < 0 and then goto error.

ZeroIntensity · 2024-11-18T16:01:16Z

Modules/_ctypes/cfield.c

- if (bit_size){
+ if (bit_size_obj != Py_None){
+
+ Py_ssize_t bit_size;


Lint is complaining about this. I'm assuming this just needs to get moved to before the if

.pre-commit-config.yaml

Co-Authorsd-By: Peter Bierma <[email protected]>

encukou · 2024-12-04T10:37:40Z

OK. Thank you for the fix!
I hope you don't mind me pushing to your branch -- this way I can keep changes in this PR, with the discussion.

encukou · 2024-12-09T12:37:31Z

@serhiy-storchaka, should I wait for your review?

serhiy-storchaka · 2024-12-09T12:40:23Z

I am looking.

serhiy-storchaka

Ah, this is the same PR. As I said in the issue, it fixes some symptoms, but there is a deeper issue.

serhiy-storchaka · 2024-12-09T12:45:21Z

Modules/_ctypes/stgdict.c

 goto error;
 }
- Py_ssize_t total_size = PyLong_AsInt(tmp);
+ Py_ssize_t total_size = PyLong_AsSsize_t(tmp);


What was a reason for using PyLong_AsInt(). This is a new API, so it unlikely was accident. Is there a limitation on total_size to be in the range of int?

It was an accident -- my mistake.

serhiy-storchaka · 2024-12-09T12:47:00Z

Modules/_ctypes/cfield.c

+ // Currently, the bit size is specified redundantly
+ // in NUM_BITS(size) and bit_size_obj.
+ // Verify that they match.
+ assert(PyLong_AsSsize_t(bit_size_obj) == bit_size);


Can this be guaranteed? What if bit_size_obj is not None and is not an int?

It can.
The implementation is split between internal Python code in ctypes._layout, and C code here. They are currently tightly coupled. The assert also verifies the Python part.

encukou · 2024-12-09T14:14:19Z

As I said in the issue, it fixes some symptoms, but there is a deeper issue.

Yes. The important thing in this PR is the regression test (and fixing the test for now).
I plan to improve the code further: see #127297 for the next step, a refactoring to make future work easier. After that's in I plan to split up the size and bitfield info.

vstinner

LGTM

miss-islington-app · 2024-12-10T13:43:20Z

Thanks @Melissa0x1f992 for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

miss-islington-app · 2024-12-10T13:43:21Z

Thanks @Melissa0x1f992 for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

miss-islington-app · 2024-12-10T13:43:26Z

Sorry, @Melissa0x1f992 and @encukou, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker cef0a90d8f3a94aa534593f39b4abf98165675b9 3.13

miss-islington-app · 2024-12-10T13:43:30Z

Sorry, @Melissa0x1f992 and @encukou, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker cef0a90d8f3a94aa534593f39b4abf98165675b9 3.12

…ythonGH-126938) This backports the test from pythonGH-126938, with changed limit and exception class. Co-authored-by: Melissa0x1f992 <[email protected]> Co-authored-by: Peter Bierma <[email protected]> Co-authored-by: Terry Jan Reedy <[email protected]> Co-authored-by: Petr Viktorin <[email protected]>

bedevere-app · 2024-12-11T13:27:33Z

GH-127825 is a backport of this pull request to the 3.13 branch.

…GH-126938) (GH-127825) This backports the *test* from GH-126938, with changed limit and exception class. Co-authored-by: Melissa0x1f992 <[email protected]> Co-authored-by: Peter Bierma <[email protected]> Co-authored-by: Terry Jan Reedy <[email protected]>

… field (pythonGH-126938) (pythonGH-127825) This backports the *test* from pythonGH-126938, with changed limit and exception class. Co-authored-by: Melissa0x1f992 <[email protected]> Co-authored-by: Peter Bierma <[email protected]> Co-authored-by: Terry Jan Reedy <[email protected]> (cherry-picked from d51c144)

…GH-126938) (GH-127825) (GH-127909) This backports the *test* from GH-126938, with changed limit and exception class. Co-authored-by: Melissa0x1f992 <[email protected]> Co-authored-by: Peter Bierma <[email protected]> Co-authored-by: Terry Jan Reedy <[email protected]> (cherry-picked from d51c144)

…bytes (pythonGH-126938) Co-authored-by: Peter Bierma <[email protected]> Co-authored-by: Terry Jan Reedy <[email protected]> Co-authored-by: Petr Viktorin <[email protected]>

Melissa0x1f992and others added 2 commits November 17, 2024 13:21

Fix rejection when non-bitfield fields are larger than 2^16 bytes
1962567

Merge pull request#1from Melissa0x1f992/use-bitsize-param
1900cf5
Fix rejection when non-bitfield fields are larger than 2^16 bytes

bedevere-appbot added the awaiting review label Nov 17, 2024

bedevere-appbot mentioned this pull request Nov 17, 2024
Struct fields with size > 65535 bytes throw TypeError #126937
Closed

📜🤖 Added by blurb_it.
2bd972b

terryjreedy reviewed Nov 17, 2024
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Update Modules/_ctypes/cfield.c
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Melissa0x1f992and others added 3 commits November 18, 2024 07:43

Remove specific dependency on Python 3.12 for black
0d21229

Add test case for large fields
d8a6f08

Merge pull request#2from Melissa0x1f992/use-bitsize-param
16bfb44
Use bitsize param

Melissa0x1f992 requested review from AlexWaygood and hugovk as code owners November 18, 2024 13:51

Melissa0x1f992and others added 4 commits November 18, 2024 08:19

Reduce test field size to (2^31 - 1) to support 32 bit systems
7402a8f

Merge branch 'python:main' into main
8994ad0

Reduce test field size to (2^31 - 1) to support 32 bit systems
db171e0

Merge pull request#3from Melissa0x1f992/use-bitsize-param
7bc0ceb
Reduce test field size to (2^31 - 1) to support 32 bit systems

AlexWaygood reviewed Nov 18, 2024
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vstinner changed the title ~~gh-126937: Fix TypeError when a field's size is >65535 bytes~~gh-126937, ctypes: Fix TypeError when a field's size is >65535 bytesNov 19, 2024

Reword changelog
f61faa6
Co-Authorsd-By: Peter Bierma <[email protected]>

serhiy-storchaka reviewed Dec 9, 2024
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vstinner approved these changes Dec 9, 2024
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bedevere-appbot added awaiting merge and removed awaiting review labels Dec 9, 2024

serhiy-storchaka approved these changes Dec 9, 2024
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encukou merged commit cef0a90 into python:mainDec 10, 2024
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bedevere-appbot removed the awaiting merge label Dec 10, 2024

serhiy-storchaka added needs backport to 3.12 only security fixes needs backport to 3.13 bugs and security fixes labels Dec 10, 2024

miss-islington-appbot assigned encukou Dec 10, 2024

serhiy-storchaka removed needs backport to 3.12 only security fixes needs backport to 3.13 bugs and security fixes labels Dec 10, 2024

encukou mentioned this pull request Dec 11, 2024
[3.13] gh-126937: ctypes: add test for maximum size of a struct field (GH-126938) #127825
Merged

encukou mentioned this pull request Dec 13, 2024
[3.12] gh-126937: ctypes: add test for maximum size of a struct field (GH-126938) (GH-127825) #127909
Merged

encukou mentioned this pull request Jan 17, 2025
gh-128715: Expose ctypes.CField, with info attributes #128950
Merged

		@@ -0,0 +1 @@
		Fixed TypeError when a Structure's field's size is >65535 bytes

	Fixed TypeError when a Structure's field's size is >65535 bytes
	Fix :exc:`TypeError` when a :class:`ctypes.Structure` has a field size that doesn't fit into an unsigned 16-bit integer.

Uh oh!

gh-126937: ctypes: fix TypeError when a field's size is >65535 bytes#126938

gh-126937: ctypes: fix TypeError when a field's size is >65535 bytes #126938

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