I found this while writing up a separate bug (CPython doesn't use static analysis!).

In PC/launcher.c, get_env has a bug:

        /* Large environment variable. Accept some leakage */
        wchar_t *buf2 = (wchar_t*)malloc(sizeof(wchar_t) * (result+1));
        if (buf2 = NULL) {
            error(RC_NO_MEMORY, L"Could not allocate environment buffer");
        }
        GetEnvironmentVariableW(key, buf2, result);
        return buf2;

See: https://hg.python.org/cpython/file/tip/PC/launcher.c#l117


Instead of `buf2 == NULL`, Vinay Sajip wrote `buf2 = NULL`. The commit where the error was introduced: https://hg.python.org/cpython/rev/4123e002a1af

Thus, whatever value was in buf2 is lost, the branch is NOT taken (because buf2 evaluates to false), and GetEnvironmentVariableW will (probably) cause an access violation. 


Compiling with /analyze found this quite easily:

c:\pythondev\repo\pc\launcher.c(117): warning C6282: Incorrect operator:  assignment of constant in Boolean context. Consider using '==' instead.

New changeset 5015440beec2 by Vinay Sajip in branch '3.4':
Fixes #25844: Corrected =/== typo potentially leading to crash in launcher.
https://hg.python.org/cpython/rev/5015440beec2

New changeset 9552fcd303fd by Vinay Sajip in branch '3.5':
Fixes #25844: Corrected =/== typo potentially leading to crash in launcher.
https://hg.python.org/cpython/rev/9552fcd303fd

New changeset cdf8033d8820 by Vinay Sajip in branch 'default':
Fixes #25844: Merged fix from 3.5.
https://hg.python.org/cpython/rev/cdf8033d8820

To the fix for this bug we have to provoke the unsufficient memory error just at this point. This is unlikely worth.

Thank you Alexander for your reports.

New changeset 48b3cac0dbcd by Vinay Sajip in branch '3.4':
Fixes #25844: Corrected =/== typo potentially leading to crash in launcher.
https://hg.python.org/cpython/rev/48b3cac0dbcd