Issue 40309: “unmatched paren” for space before parenthesis in Py_BuildValue

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This issue has been migrated to GitHub: https://github.com/python/cpython/issues/84489

classification

Title:	“unmatched paren” for space before parenthesis in Py_BuildValue
Type:		Stage:	patch review
Components:	C API	Versions:	Python 3.8, Python 3.7

process

Status:	open	Resolution:
Dependencies:		Superseder:
Assigned To:		Nosy List:	Wrzlprmft, ZackerySpytz
Priority:	normal	Keywords:	patch

Created on 2020-04-17 08:54 by Wrzlprmft, last changed 2022-04-11 14:59 by admin.

Files
File name	Uploaded	Description	Edit
foo.c	Wrzlprmft, 2020-04-17 08:54	Minimal Python C Extension showing the bug

Pull Requests
URL	Status	Linked	Edit
PR 21158	open	ZackerySpytz, 2020-06-25 15:53

Messages (1)
msg366647 - (view)	Author: Gerrit Ansmann (Wrzlprmft)	Date: 2020-04-17 08:54
According to the C-API documentation¹ for `Py_BuildValue`: > The characters space, tab, colon and comma are ignored in format strings (but not within format units such as s#). This can be used to make long format strings a tad more readable. However format strings such as `"(d )"` cause the error: > Unmatched paren in format By contrast `"( d)"` and `"(d d)"` cause no problems. I therefore assume that tuples are not considered “format units” in the sense of the above quote and this is a bug. Alternatively, the documentation needs clarification. I could reproduce this problem with Python 3.7 and 3.8. I did not try other versions. Appended is a minimal C extension exhibiting the problem. I compile and run with: gcc -fPIC -I/usr/include/python3.8 -c foo.c -o foo.o gcc -shared foo.o -o foo.so python3.8 -c "import foo; foo.bar()" ---- ¹ https://docs.python.org/3/c-api/arg.html

msg366647 - (view)

Author: Gerrit Ansmann (Wrzlprmft)

Date: 2020-04-17 08:54

According to the C-API documentation¹ for `Py_BuildValue`:

> The characters space, tab, colon and comma are ignored in format strings (but not within format units such as s#). This can be used to make long format strings a tad more readable.

However format strings such as `"(d )"` cause the error:

> Unmatched paren in format

By contrast `"( d)"` and `"(d d)"` cause no problems. I therefore assume that tuples are not considered “format units” in the sense of the above quote and this is a bug. Alternatively, the documentation needs clarification.

I could reproduce this problem with Python 3.7 and 3.8. I did not try other versions.

Appended is a minimal C extension exhibiting the problem. I compile and run with:

gcc -fPIC -I/usr/include/python3.8 -c foo.c -o foo.o
gcc -shared foo.o -o foo.so
python3.8 -c "import foo; foo.bar()"

----

¹ https://docs.python.org/3/c-api/arg.html

History
Date	User	Action	Args
2022-04-11 14:59:29	admin	set	github: 84489
2020-06-25 15:53:09	ZackerySpytz	set	keywords: + patch nosy: + ZackerySpytz pull_requests: + pull_request20318 stage: patch review
2020-04-17 08:54:27	Wrzlprmft	create