Incorrect error handling for APIs that can raise exceptions

[erlend-aasland]

For example, in the collation callback two str objects (string1 and string2) are created using PyUnicode_FromStringAndSize. Error handling should happen directly after each call to PyUnicode_FromStringAndSize:

cpython/Modules/_sqlite/connection.c

Lines 1870 to 1875 in 0cb6b9b

	string1 = PyUnicode_FromStringAndSize((const char*)text1_data, text1_length);
	string2 = PyUnicode_FromStringAndSize((const char*)text2_data, text2_length);
	if (!string1 || !string2) {
	goto finally; /* failed to allocate strings */
	}

Other cases where error handling is not done immediately after the API has been used:

• gh-105375: Improve error handling in PyUnicode_BuildEncodingMap() #105491
• gh-105375: Improve error handling in compiler_enter_scope() #105494
• gh-105375: Improve error handling in the builtins extension module #105585
• gh-105375: Improve errnomodule error handling #105590
• gh-105375: Improve error handling in _elementtree #105591
• gh-105375: Improve posix error handling #105592
• gh-105375: Improve error handling in _ctypes #105593
• gh-105375: Improve array.array exception handling #105594
• gh-105375: Improve error handling in _Unpickler_SetInputStream() #105667
• gh-105375: Improve _pickle error handling #105475
• gh-105375: Harden _ssl initialisation #105599
• gh-105375: Improve error handling in zoneinfo module #105586
• gh-105375: Harden _datetime initialisation #105604
• gh-105375: Harden pyexpat initialisation #105606
• gh-105375: Improve _decimal error handling #105605
• gh-105375: Harden error handling in _testcapi/heaptype.c #105608
• gh-105375: Improve PyErr_WarnExplicit() error handling #105610
• gh-105375: Improve error handling in the sys extension module #105611

I might have missed some; I did not do a complete audit yet.

Linked PRs

• gh-105375: Improve error handling in sqlite3 collation callback #105412
• [3.12] gh-105375: Improve error handling in sqlite3 collation callback (GH-105412) #105440
• [3.11] gh-105375: Improve error handling in sqlite3 collation callback (GH-105412) #105441
• gh-105375: Improve _pickle error handling #105475
• gh-105375: Improve error handling in PyUnicode_BuildEncodingMap() #105491
• gh-105375: Improve error handling in compiler_enter_scope() #105494
• [3.12] gh-105375: Improve error handling in compiler_enter_scope() (GH-105494) #105581
• [3.11] gh-105375: Improve error handling in compiler_enter_scope() (#105494) #105582
• [3.11] gh-105375: Improve _pickle error handling (#105475) #105583
• [3.12] gh-105375: Improve _pickle error handling (#105475) #105584
• gh-105375: Improve error handling in the builtins extension module #105585
• gh-105375: Improve error handling in zoneinfo module #105586
• gh-105375: Improve errnomodule error handling #105590
• gh-105375: Improve error handling in _elementtree #105591
• gh-105375: Improve posix error handling #105592
• gh-105375: Improve error handling in _ctypes #105593
• gh-105375: Improve array.array exception handling #105594
• [3.12] gh-105375: Improve errnomodule error handling (#105590) #105596
• [3.11] gh-105375: Improve posix error handling (GH-105592) #105597
• [3.12] gh-105375: Improve posix error handling (GH-105592) #105598
• gh-105375: Harden _ssl initialisation #105599
• [3.12] gh-105375: Improve error handling in _elementtree (GH-105591) #105600
• [3.11] gh-105375: Improve error handling in _elementtree (GH-105591) #105601
• gh-105375: Harden _datetime initialisation #105604
• gh-105375: Improve _decimal error handling #105605
• gh-105375: Harden error handling in _testcapi/heaptype.c #105608
• gh-105375: Improve PyErr_WarnExplicit() error handling #105610
• gh-105375: Improve error handling in the sys extension module #105611
• [3.12] gh-105375: Improve error handling in zoneinfo module (GH-105586) #105612
• [3.11] gh-105375: Improve error handling in zoneinfo module (GH-105586) #105613
• [3.12] gh-105375: Harden error handling in _testcapi/heaptype.c (GH-105608) #105615
• [3.12] gh-105375: Harden _ssl initialisation (GH-105599) #105642
• [3.11] gh-105375: Improve array.array exception handling (GH-105594) #105643
• [3.12] gh-105375: Improve array.array exception handling (GH-105594) #105644
• [3.12] gh-105375: Harden _datetime initialisation (GH-105604) #105645
• [3.11] gh-105375: Harden _datetime initialisation (GH-105604) #105646
• [3.12] gh-105375: Improve _decimal error handling (GH-105605) #105647
• [3.11] gh-105375: Improve _decimal error handling (GH-105605) #105648
• [3.12] gh-105375: Improve error handling in the builtins extension module (GH-105585) #105649
• [3.11] gh-105375: Improve error handling in the builtins extension module (GH-105585) #105650
• [3.11] gh-105375: Harden _ssl initialisation (#105599) #105651
• [3.12] gh-105375: Improve PyErr_WarnExplicit() error handling (GH-105610) #105659
• [3.11] gh-105375: Improve PyErr_WarnExplicit() error handling (GH-105610) #105660
• [3.12] gh-105375: Improve error handling in PyUnicode_BuildEncodingMap() (GH-105491) #105661
• [3.11] gh-105375: Improve error handling in PyUnicode_BuildEncodingMap() (GH-105491) #105662
• [3.12] gh-105375: Improve error handling in _ctypes (GH-105593) #105663
• [3.11] gh-105375: Improve error handling in _ctypes (GH-105593) #105664
• [3.12] gh-105375: Improve error handling in the sys extension module (GH-105611) #105665
• [3.11] gh-105375: Improve error handling in the sys extension module (#105611) #105666
• gh-105375: Improve error handling in _Unpickler_SetInputStream() #105667
• [3.11] gh-105375: Harden pyexpat initialisation (#105606) #105668
• [3.12] gh-105375: Harden pyexpat initialisation (#105606) #105669
• gh-105375: Explicitly initialise all {Pickler,Unpickler}Object fields #105686
• [3.12] gh-105375: Explicitly initialise all {Pickler,Unpickler}Object fields (GH-105686) #105710
• [3.11] gh-105375: Explicitly initialise all {Pickler,Unpickler}Object fields (#105686) #105711
• [3.12] gh-105375: Improve error handling in _Unpickler_SetInputStream() (#105667) #105720
• [3.11] gh-105375: Improve error handling in _Unpickler_SetInputStream() (#105667) #105721

[vstinner]

There were many "init" functions of C extensions calling all C functions without checking for exceptions, and only checking for exceptions once at the end. Most of them have been fixed with better error checking, but not all of them yet.

[vstinner]

See issue #105374 about C API being error prone: when it's unclear if passing NULL was done on purpose or by mistake

[vstinner]

See also capi-workgroup/problems#47

[serhiy-storchaka]

Thank you, @erlend-aasland. These are minor errors, but it is nice to have the code cleaner.

Although you introduced new bugs in #105475 and #105611 related to clearing non-initialized references.

[erlend-aasland]

Thanks for double-checking, Serhiy. I really appreciate that. I will address your remarks.

[sobolevn]

Refs #105673