diff -Nru xdvik-ja-22.87.06+j1.42/debian/changelog xdvik-ja-22.87.06+j1.42/debian/changelog
--- xdvik-ja-22.87.06+j1.42/debian/changelog	2024-03-29 14:38:50.000000000 +0530
+++ xdvik-ja-22.87.06+j1.42/debian/changelog	2026-05-23 21:24:48.000000000 +0530
@@ -1,3 +1,15 @@
+xdvik-ja (22.87.06+j1.42-3.1) unstable; urgency=medium
+
+  * Non-maintainer upload.
+  * Fix FTBFS with GCC 15 / C23 (Closes: #1098134): remove stale
+    `extern void exit()` declaration in texk/xdvik/squeeze/squeeze.c.
+    In C23 mode, empty parameter lists no longer match any-argument
+    signatures, so this declaration conflicts with <stdlib.h>'s
+    `void exit(int)`, causing four fatal errors.  <stdlib.h> is already
+    included and provides the correct prototype.
+
+ -- Azeez Syed <azeezalishah@gmail.com>  Sat, 23 May 2026 21:24:48 +0530
+
 xdvik-ja (22.87.06+j1.42-3) unstable; urgency=medium
 
   [ Debian Janitor ]
diff -Nru xdvik-ja-22.87.06+j1.42/debian/patches/0014-fix-ftbfs-gcc15.patch xdvik-ja-22.87.06+j1.42/debian/patches/0014-fix-ftbfs-gcc15.patch
--- xdvik-ja-22.87.06+j1.42/debian/patches/0014-fix-ftbfs-gcc15.patch	1970-01-01 05:30:00.000000000 +0530
+++ xdvik-ja-22.87.06+j1.42/debian/patches/0014-fix-ftbfs-gcc15.patch	2026-05-23 21:24:48.000000000 +0530
@@ -0,0 +1,131 @@
+Description: Fix FTBFS with GCC 15 / C23: remove stale extern declarations and
+ fix untyped function-pointer parameters
+ In C23 (GCC 15 default), empty parameter lists `()` no longer mean
+ "unspecified parameters" — they mean "no parameters".  This breaks several
+ places in the xdvik source that rely on the old behaviour:
+ .
+ * squeeze/squeeze.c: `extern void exit()` conflicts with <stdlib.h>'s
+   `exit(int)`, which is already included.  Remove the stale local decl.
+ * dvi-draw.c: `extern off_t lseek()` and `extern double pow()` likewise
+   conflict with kpathsea/c-unistd.h and <math.h> respectively.  Remove them.
+ * gui/menu.h, gui/menu.c: the `set_menu` and `set_menu_info` functions take a
+   callback `Boolean (*cmp)()` that is always passed a `(void *, const char *)`
+   function (check_toggle, check_int, etc., all declared in events.h:226-230).
+   Spell out the correct type to satisfy C23's stricter function-pointer rules.
+ * gui/sfDraw.c: `extern int SFchdir()` inside SFstatAndCheck() is redundant —
+   sfPath.h (included at the top of the file) already declares
+   `int SFchdir(const char *path)`.  Remove the local forward declaration.
+ * gui/Panner.c: `extern Bool XmuDistinguishablePixels()` is called with four
+   arguments; the comment "not defined in any Xmu headers" is now incorrect —
+   the prototype lives in <X11/Xmu/StdCmap.h>.  Replace the wrong extern with
+   the proper include.
+Author: Azeez Syed <azeezalishah@gmail.com>
+Bug-Debian: https://bugs.debian.org/1098134
+Forwarded: not-needed
+Last-Update: 2026-05-23
+
+--- a/texk/xdvik/squeeze/squeeze.c
++++ b/texk/xdvik/squeeze/squeeze.c
+@@ -118,8 +118,6 @@ main(int argc, char *argv[])
+     int c;
+     char *b;
+     char seeking;
+-    extern void exit();
+-
+     if (argc > 3 || (in = (argc < 2 ? stdin : fopen(argv[1], "r"))) == NULL ||
+ 	(out = (argc < 3 ? stdout : fopen(argv[2], "w"))) == NULL) {
+ 	(void)fprintf(stderr, "Usage:  squeeze [infile [outfile]]\n");
+--- a/texk/xdvik/dvi-draw.c
++++ b/texk/xdvik/dvi-draw.c
+@@ -201,8 +201,6 @@ bmUnitT bit_masks[] = {
+ #ifdef	VMS
+ #define	off_t	int
+ #endif
+-extern off_t lseek();
+-
+ #ifndef	SEEK_SET	/* if <unistd.h> is not provided (or for <X11R5) */
+ #define	SEEK_SET	0
+ #define	SEEK_CUR	1
+@@ -5239,8 +5237,6 @@ anchor_search(const char *str)
+ 
+ #if GREY
+ 
+-extern	double	pow();
+-
+ static void
+ mask_shifts(Pixel mask, int *pshift1, int *pshift2)
+ {
+--- a/texk/xdvik/gui/menu.c
++++ b/texk/xdvik/gui/menu.c
+@@ -62,7 +62,7 @@ static struct button_info *m_button_info
+ 
+ 
+ static void
+-set_menu_info(void *val, XtActionProc proc, Boolean (*cmp)(), struct button_info *item)
++set_menu_info(void *val, XtActionProc proc, Boolean (*cmp)(void *, const char *), struct button_info *item)
+ {
+     size_t i;
+     ASSERT(item != NULL, "item in set_menu_info must'nt be NULL!");
+@@ -96,7 +96,7 @@ set_menu_info(void *val, XtActionProc pr
+ 
+ /* set a menu according to val and the compare function cmp */
+ void
+-set_menu(void *val, XtActionProc proc, Boolean (*cmp)())
++set_menu(void *val, XtActionProc proc, Boolean (*cmp)(void *, const char *))
+ {
+     /* removed following since cast from function pointer to void pointer is not supported by ANSI C */
+     /* TRACE_GUI((stderr, "set_menu_info: %d, %p, %p", *(int *)val, (void *)proc, (void *)cmp)); */
+--- a/texk/xdvik/gui/menu.h
++++ b/texk/xdvik/gui/menu.h
+@@ -67,6 +67,6 @@ extern void create_menu_buttons(Widget p
+ #endif
+ 				);
+ 
+-extern void set_menu(void *val, XtActionProc proc, Boolean (*cmp)());
++extern void set_menu(void *val, XtActionProc proc, Boolean (*cmp)(void *, const char *));
+ 
+ #endif /* MENU_H_ */
+--- a/texk/xdvik/gui/Panner.c
++++ b/texk/xdvik/gui/Panner.c
+@@ -46,7 +46,7 @@
+ #include <X11/Xmu/Drawing.h>
+ #include <ctype.h>			/* for isascii() etc. */
+ 
+-extern Bool XmuDistinguishablePixels(); /* not defined in any Xmu headers */
++#include <X11/Xmu/StdCmap.h>		/* for XmuDistinguishablePixels() */
+ 
+ #if HAVE_XKB_BELL_EXT
+ # include <X11/XKBlib.h>
+--- a/texk/xdvik/gui/sfDraw.c
++++ b/texk/xdvik/gui/sfDraw.c
+@@ -238,8 +238,6 @@ SFstatAndCheck(SFDir *dir, SFEntry *entr
+     struct stat statBuf;
+     char save;
+     int last;
+-    extern int SFchdir();
+-
+     /*
+      * must be restored before returning
+      */
+--- a/texk/xdvik/gui/sfDraw.h
++++ b/texk/xdvik/gui/sfDraw.h
+@@ -56,7 +56,7 @@ void SFhAreaSelectedCallback(Widget w, i
+ void SFpathSliderMovedCallback(Widget w, XtPointer client_data, float *new);
+ void SFpathAreaSelectedCallback(Widget w, XtPointer client_data, int pnew);
+ Boolean SFworkProc(void);
+-extern int (*SFfunc)();
++extern int (*SFfunc)(char *, char **, struct stat *);
+ 
+ extern Widget selFileField, selFileForm, selFileHScroll, selFileHScrolls[], selFileLists[], selFileVScrolls[];
+ extern Display *SFdisplay;
+--- a/texk/xdvik/gui/sfSelFile.c
++++ b/texk/xdvik/gui/sfSelFile.c
+@@ -125,7 +125,7 @@ XtAppContext SFapp;
+ int SFpathScrollWidth, SFvScrollHeight, SFhScrollWidth;
+ char SFtextBuffer[MAXPATHLEN];
+ XtIntervalId SFdirModTimerId;
+-int (*SFfunc) ();
++int (*SFfunc)(char *, char **, struct stat *);
+ 
+ static int SFstatus = SEL_FILE_NULL;
+ 
diff -Nru xdvik-ja-22.87.06+j1.42/debian/patches/series xdvik-ja-22.87.06+j1.42/debian/patches/series
--- xdvik-ja-22.87.06+j1.42/debian/patches/series	2023-10-13 14:09:33.000000000 +0530
+++ xdvik-ja-22.87.06+j1.42/debian/patches/series	2026-05-23 21:24:48.000000000 +0530
@@ -13,3 +13,4 @@
 0013-Follow-gs9.27-changes-execute-was-dropped.patch
 use-after-free.patch
 Add_2004_into_config.xdvi
+0014-fix-ftbfs-gcc15.patch