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plugins: fix error_string construction#2273

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plugins: fix error_string construction#2273
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florian-at-bareos:dev/fburger/master/fix-error-strings

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@florian-at-bareos florian-at-bareos commented May 13, 2025 •
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This PR fixes a bug introduced with commit ce9f5bc, see #225.

PyUnicode_AsUTF8 can return NULL and doing std::string(NULL) will crash.
With the changes of this PR we explicitly do a null-pointer check before constructing a std::string.

Fixes bareos/internal#225: ce9f5bc introduces creation of std::string from potential nullptr

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@florian-at-bareos florian-at-bareos added this to the 25.0.0 milestone May 13, 2025
@florian-at-bareos florian-at-bareos self-assigned this May 13, 2025
@florian-at-bareos florian-at-bareos force-pushed the dev/fburger/master/fix-error-strings branch from c27c142 to c5e0a51 Compare May 13, 2025 12:05
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Looks good. Just added a small nit to think about.

@florian-at-bareos florian-at-bareos force-pushed the dev/fburger/master/fix-error-strings branch from c5e0a51 to ff9fe57 Compare May 21, 2025 14:37
@florian-at-bareos florian-at-bareos marked this pull request as ready for review May 23, 2025 10:08
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florian-at-bareos commented Jun 4, 2025 •
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If I interpret this correctly type == NULL implies that value == NULL and traceback == NULL, see https://docs.python.org/3/c-api/exceptions.html#c.PyErr_Fetch.

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sebsura commented Jun 4, 2025

That is true, but as we do not check whether traceback or value are null before calling the function, we can still pass a null type into the python function.

Looking into the cpython doc i get the following (for Py_BuildValue):

O (object) [PyObject *]

    Pass a Python object untouched but create a new [strong reference](https://docs.python.org/3/glossary.html#term-strong-reference) to it (i.e. its reference count is incremented by one).
    If the object passed in is a NULL pointer, it is assumed that this was caused because the call producing the argument found an error and set an exception.
    Therefore, [Py_BuildValue()](https://docs.python.org/3/c-api/arg.html#c.Py_BuildValue) will return NULL but won’t raise an exception.
    If no exception has been raised yet, [SystemError](https://docs.python.org/3/library/exceptions.html#SystemError) is set.

so this isnt fatal, but still not great. It looks like we should also be using Py_Restore(...) once we are dont with the result of Py_Fetch(...), so its probably best to just leave this as is and rework it completely at a later point.
After all almost all of these functions are deprecated in 3.12, so this will need to get replaced soon anyways.

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sebsura commented Jun 4, 2025

Looks like github didnt show me your last commit, so now there is actually a check for that :)

@florian-at-bareos florian-at-bareos force-pushed the dev/fburger/master/fix-error-strings branch from 72f6bbf to 5d9109d Compare June 4, 2025 14:42
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@florian-at-bareos florian-at-bareos force-pushed the dev/fburger/master/fix-error-strings branch from 5d9109d to fa62001 Compare June 5, 2025 06:24
florian-at-bareos and others added 2 commits June 5, 2025 07:09
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plugins: fix error_string construction
9ca0120 
PyUnicode_AsUTF8 can return NULL and doing std::string(NULL) will crash.

Fixes bareos#225: ce9f5bc introduces creation of std::string from
potential nullptr
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Update CHANGELOG.md
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@BareosBot BareosBot force-pushed the dev/fburger/master/fix-error-strings branch from 761d6f9 to 1fa6413 Compare June 5, 2025 07:09
@BareosBot BareosBot merged commit 169dd92 into bareos:master Jun 5, 2025
@sebsura sebsura mentioned this pull request Jun 24, 2025
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