Documentation example of module init function lacks error handling

@scoder

BPO	40279
Nosy	@scoder, @caje731
PRs	bpo-40279 Add some error-handling to the module initialisation example #19705 [3.8] bpo-40279: Add some error-handling to the module initialisation docs example (GH-19705) #19710

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GitHub fields:

assignee = None
closed_at = <Date 2020-04-25.05:46:25.518>
created_at = <Date 2020-04-14.06:08:29.273>
labels = ['easy', 'type-feature', '3.8', '3.9', 'docs']
title = 'Documentation example of module init function lacks error handling'
updated_at = <Date 2020-04-25.05:46:25.517>
user = 'https://github.com/scoder'

bugs.python.org fields:

activity = <Date 2020-04-25.05:46:25.517>
actor = 'scoder'
assignee = 'docs@python'
closed = True
closed_date = <Date 2020-04-25.05:46:25.518>
closer = 'scoder'
components = ['Documentation']
creation = <Date 2020-04-14.06:08:29.273>
creator = 'scoder'
dependencies = []
files = []
hgrepos = []
issue_num = 40279
keywords = ['patch', 'easy', 'newcomer friendly']
message_count = 5.0
messages = ['366368', '367234', '367257', '367258', '367259']
nosy_count = 3.0
nosy_names = ['scoder', 'docs@python', 'cajetan.rodrigues']
pr_nums = ['19705', '19710']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue40279'
versions = ['Python 3.8', 'Python 3.9']

The example in the docs that shows how to initialise an embedded module gives a wrong impression about error handling. Most of the functions that it calls return error codes, but those do not get looked at. Innocent users who copy and paste the example may miss some of them when adapting the code, thus ending up with an unsafe implementation.

The example should at least make it clear where error handling is needed.

https://docs.python.org/3/extending/extending.html#the-module-s-method-table-and-initialization-function

int
main(int argc, char *argv[])
{
    wchar_t *program = Py_DecodeLocale(argv[0], NULL);
    if (program == NULL) {
        fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
        exit(1);
    }

    /* Add a built-in module, before Py_Initialize */
    PyImport_AppendInittab("spam", PyInit_spam);

    /* Pass argv[0] to the Python interpreter */
    Py_SetProgramName(program);

    /* Initialize the Python interpreter.  Required. */
    Py_Initialize();

    /* Optionally import the module; alternatively,
       import can be deferred until the embedded script
       imports it. */
    PyImport_ImportModule("spam");

...

    PyMem_RawFree(program);
    return 0;
}

At the risk of sounding like a jerk, I'd very much want to say that copy-pasters should get what they deserve :) But then I remember I was once a copy-paster too!

Hello again, Stefan :)

Thanks for watching out for the community - I'll be happy to fix this!

New changeset d4f3923 by Cajetan Rodrigues in branch 'master':
bpo-40279: Add some error-handling to the module initialisation docs example (GH-19705)
d4f3923

New changeset 882a7f4 by Miss Islington (bot) in branch '3.8':
bpo-40279: Add some error-handling to the module initialisation docs example (GH-19705) (GH-19710)
882a7f4

Hi Cajetan, thank you for your contribution! That's a nice documentation improvement.

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Documentation example of module init function lacks error handling #84460

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Documentation example of module init function lacks error handling #84460

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scoder commented on Apr 14, 2020

caje731 commented on Apr 24, 2020

scoder commented on Apr 25, 2020

scoder commented on Apr 25, 2020

scoder commented on Apr 25, 2020

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