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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Tkinter: incompatible pointer types warnings when built with Tcl 9","articleBody":"Tcl/Tk 9 changes C APIs to use a different type for sizes to allow transferring ≥32-bit sized things. The new type is `Tcl_Size`, which as of [TIP 660](https://core.tcl-lang.org/tips/doc/trunk/tip/660.md) is defined as either `ptrdiff_t` in Tcl 9, or `int` in Tcl 8.7 for binary compatibility.\r\n\r\nMy impression is that Tcl/Tk wrappers such as Tkinter, which are primarily used for Tk GUI, have little if any need for this. But as of [TIP 664](https://core.tcl-lang.org/tips/doc/trunk/tip/664.md), usage of APIs which previously expected `int *` must be updated for Tcl 9. There was previously effort in Tcl to continue allowing `int *` usage for compatibility, and maybe that would have been good enough for Tkinter, but others in the Tcl/Tk inner circle (who already wish to abandon Tcl/Tk \u003c 9 entirely) rejected that approach. `-Wincompatible-pointer-types` warnings now seen under Tcl 9:\r\n\r\n```\r\n./Modules/_tkinter.c:504:21: warning: incompatible pointer types passing 'int *' to parameter of type 'Tcl_Size *' (aka 'long *') [-Wincompatible-pointer-types]\r\n  504 |     const char *s = Tcl_GetStringFromObj(value, \u0026len);\r\n      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\ntcl90/include/tclDecls.h:4235:36: note: expanded from macro 'Tcl_GetStringFromObj'\r\n 4235 |                 (Tcl_GetStringFromObj)((objPtr), (sizePtr)))\r\n      |                                                  ^~~~~~~~~\r\ntcl90/include/tclDecls.h:1754:15: note: passing argument to parameter 'lengthPtr' here\r\n 1754 |                                 Tcl_Size *lengthPtr);\r\n      |                                           ^\r\n./Modules/_tkinter.c:1138:29: warning: incompatible pointer types passing 'int *' to parameter of type 'Tcl_Size *' (aka 'long *') [-Wincompatible-pointer-types]\r\n 1138 |         char *data = (char*)Tcl_GetByteArrayFromObj(value, \u0026size);\r\n      |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\ntcl90/include/tclDecls.h:4229:41: note: expanded from macro 'Tcl_GetByteArrayFromObj'\r\n 4229 |                 (Tcl_GetBytesFromObj)(NULL, (objPtr), (sizePtr)))\r\n      |                                                       ^~~~~~~~~\r\ntcl90/include/tclDecls.h:1751:32: note: passing argument to parameter 'numBytesPtr' here\r\n 1751 |                                 Tcl_Obj *objPtr, Tcl_Size *numBytesPtr);\r\n      |                                                            ^\r\n./Modules/_tkinter.c:1168:18: warning: incompatible pointer types passing 'int *' to parameter of type 'Tcl_Size *' (aka 'long *') [-Wincompatible-pointer-types]\r\n 1168 |         status = Tcl_ListObjLength(interp, value, \u0026size);\r\n      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\ntcl90/include/tclDecls.h:4244:44: note: expanded from macro 'Tcl_ListObjLength'\r\n 4244 |                 (Tcl_ListObjLength)((interp), (listPtr), (lengthPtr)))\r\n      |                                                          ^~~~~~~~~~~\r\ntcl90/include/tclDecls.h:1790:33: note: passing argument to parameter 'lengthPtr' here\r\n 1790 |                                 Tcl_Obj *listPtr, Tcl_Size *lengthPtr);\r\n      |                                                             ^\r\n./Modules/_tkinter.c:2104:13: warning: incompatible pointer types passing 'int *' to parameter of type 'Tcl_Size *' (aka 'long *') [-Wincompatible-pointer-types]\r\n 2104 |         if (Tcl_ListObjGetElements(Tkapp_Interp(self),\r\n      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\n 2105 |                                    ((PyTclObject*)arg)-\u003evalue,\r\n      |                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\n 2106 |                                    \u0026objc, \u0026objv) == TCL_ERROR) {\r\n      |                                    ~~~~~~~~~~~~~\r\ntcl90/include/tclDecls.h:4241:49: note: expanded from macro 'Tcl_ListObjGetElements'\r\n 4241 |                 (Tcl_ListObjGetElements)((interp), (listPtr), (objcPtr), (objvPtr)))\r\n      |                                                               ^~~~~~~~~\r\ntcl90/include/tclDecls.h:1786:33: note: passing argument to parameter 'objcPtr' here\r\n 1786 |                                 Tcl_Obj *listPtr, Tcl_Size *objcPtr,\r\n      |                                                             ^\r\n./Modules/_tkinter.c:2136:9: warning: incompatible pointer types passing 'int *' to parameter of type 'Tcl_Size *' (aka 'long *') [-Wincompatible-pointer-types]\r\n 2136 |     if (Tcl_SplitList(Tkapp_Interp(self), list,\r\n      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\n 2137 |                       \u0026argc, \u0026argv) == TCL_ERROR)  {\r\n      |                       ~~~~~~~~~~~~~\r\ntcl90/include/tclDecls.h:4250:40: note: expanded from macro 'Tcl_SplitList'\r\n 4250 |                 (Tcl_SplitList)((interp), (listStr), (argcPtr), (argvPtr)))\r\n      |                                                      ^~~~~~~~~\r\ntcl90/include/tclDecls.h:1796:36: note: passing argument to parameter 'argcPtr' here\r\n 1796 |                                 const char *listStr, Tcl_Size *argcPtr,\r\n      |                                                                ^\r\n5 warnings generated.\r\n```\r\n\r\nCode intending to remain compatible with Tcl 8.6 is suggested to use the following after including tcl.h:\r\n\r\n```\r\n#ifndef TCL_SIZE_MAX\r\ntypedef int Tcl_Size;\r\n# define Tcl_GetSizeIntFromObj Tcl_GetIntFromObj\r\n# define Tcl_NewSizeIntObj Tcl_NewIntObj\r\n# define TCL_SIZE_MAX      INT_MAX\r\n# define TCL_SIZE_MODIFIER \"\"\r\n#endif\r\n```\r\n\r\nI intend to open a PR updating _tkinter.c to pass `Tcl_Size *` where needed.\r\n\r\nThere are several other instances where Tkinter assumes Tcl expects`int` or something not larger than `INT_MAX`, but migrating those to `Tcl_Size` and `TCL_SIZE_MAX` seems optional.\r\n\r\n\u003c!-- gh-linked-prs --\u003e\r\n### Linked PRs\r\n* gh-112681\r\n* gh-120208\n* gh-120209\n\u003c!-- /gh-linked-prs --\u003e\r\n","author":{"url":"https://github.com/chrstphrchvz","@type":"Person","name":"chrstphrchvz"},"datePublished":"2023-12-03T20:19:54.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/112672/cpython/issues/112672"}