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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Calling pyplot.show() with TkAgg backend on x86 machine raises OverflowError.","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\n**Bug summary**\r\n\r\nCalling `pyplot.show()` with TkAgg backend on x86 machine raises `OverflowError`.\r\n\r\nThe format provided to `PyArg_ParseTuple` in `mpl_tk_blit()` in file _tkagg.cpp (`\"ns(iin)(iiii)(iiii):blit\"`) causes the third element in the third argument to `blit()` (`dataptr[2]`) to convert to a `Py_ssize_t`. A 32-bit `Py_ssize_t` will not accommodate a value greater than or equal to 2^31. I consistently see values outside this range for the third element in `dataptr` (see PDB output below).\r\n\r\nChanging `iin` in the format to `iik` (`dataptr[2]` to `unsigned long`) fixes this problem for me but it may cause problems under other conditions or architectures.\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nfrom matplotlib import pyplot as plt\r\n\r\nx = [1, 2, 3, 4]\r\ny = [1, 4, 9, 16]\r\n\r\nplt.plot(x, y)\r\nplt.show()\r\n```\r\n\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n```\r\nException in Tkinter callback\r\nTraceback (most recent call last):\r\n  File \"/usr/local/lib/python3.7/tkinter/__init__.py\", line 1702, in __call__\r\n    return self.func(*args)\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py\", line 267, in resize\r\n    self.draw()\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/backends/backend_tkagg.py\", line 10, in draw\r\n    _backend_tk.blit(self._tkphoto, self.renderer._renderer, (0, 1, 2, 3))\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py\", line 91, in blit\r\n    photoimage.tk.interpaddr(), str(photoimage), dataptr, offsets, bboxptr)\r\nOverflowError: Python int too large to convert to C ssize_t\r\nException in Tkinter callback\r\nTraceback (most recent call last):\r\n  File \"/usr/local/lib/python3.7/tkinter/__init__.py\", line 1702, in __call__\r\n    return self.func(*args)\r\n  File \"/usr/local/lib/python3.7/tkinter/__init__.py\", line 746, in callit\r\n    func(*args)\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py\", line 346, in idle_draw\r\n    self.draw()\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/backends/backend_tkagg.py\", line 10, in draw\r\n    _backend_tk.blit(self._tkphoto, self.renderer._renderer, (0, 1, 2, 3))\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py\", line 91, in blit\r\n    photoimage.tk.interpaddr(), str(photoimage), dataptr, offsets, bboxptr)\r\nOverflowError: Python int too large to convert to C ssize_t\r\n```\r\n\r\nArguments to blit() from PDB:\r\n```\r\n\u003e /usr/local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py(91)blit()\r\n-\u003e photoimage.tk.interpaddr(), str(photoimage), dataptr, offsets, bboxptr)\r\n(Pdb) p photoimage.tk.interpaddr()\r\n170396608\r\n(Pdb) p str(photoimage)\r\n'pyimage10'\r\n(Pdb) p dataptr\r\n(480, 640, 2990080008)\r\n(Pdb) p offsets\r\n(0, 1, 2, 3)\r\n(Pdb) p bboxptr\r\n(0, 640, 0, 480)\r\n```\r\n\r\n**Expected outcome**\r\n\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n\u003c!--If this used to work in an earlier version of Matplotlib, please note the version it used to work on--\u003e\r\nA graph mapping [1, 2, 3, 4] to [1, 4, 9, 16].\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Slackware Linux 14.2, kernel 4.4.157\r\n  * Matplotlib version: 3.0.0 (via pip)\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): TkAgg\r\n  * Python version: 3.7.0 (from source, compiled with gcc)\r\n  * Jupyter version (if applicable):\r\n  * Other libraries: numpy 1.15.2\r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/Shooter23","@type":"Person","name":"Shooter23"},"datePublished":"2018-10-19T14:58:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/12567/matplotlib/issues/12567"}