nethack --version:dump

Add the 'dump' argument to the existing '--version' command-line
option to display the magic numbers used when validating save and
bones files for compatibility.

Nothing exciting, just a line of 5 hex values.  I was going to also
list the values for however many save and bones files are specified
on the command line but it seems to need more effort than I care to
expend.  And I hadn't made up my mind whether that should be done by
nethack, recover, or some new standalone program.  [Single line of
relatively raw output is so that they could be compared more easily.]

nethack --version:bad-argument was writing a message to stdout and
then starting play--which immediately overwrites stdout.  Have it
quit instead.  Player wasn't trying to start a game and quitting is
what it does with --version:good-argument.

dat/usagehlp

@@ -61,8 +61,10 @@ nethack --windowtype:Iii
   designation itself may be any case; variations '--windowtype Iii' and
   '-w Iii' work too.
 
-  On Windows, nethack.exe might support both tty and curses; nethackW.exe
+  On Windows, nethack.exe supports tty or curses or both depending on
-  supports mswin only.  MS-DOS is tty only.
+  settings at the time the program is built from source; nethackW.exe
+  supports mswin (also referred to as Win GUI) and optionally curses.
+  For MS-DOS, the program supports tty or curses or both.
 
 nethack -n
   don't show the 'news' file if one is present in nethack's directory.
@@ -110,13 +112,15 @@ nethack -dDir -s
 nethack --directory:Dir -s
   as above; alternate directory, if specified, should come first.
 
-nethack --version
+nethack --version or --version:copy or --version:dump or --version:show
-nethack --version:copy
+  '--version' display the program's version number plus the date and
-  '--version' display the program's version number and exit;
+  time it was built from source code, then exit;
   '--version:copy' display version number and also copy it into system
   pasteboard (should work on macOS and Windows; might not work on other
   systems) so that it could be pasted from there into a subsequent email
-  or web contact form, then exit.
+  or web contact form, then exit;
+  '--version:dump' display several internal values, then exit;
+  '--version:show' same as '--version'.
 
 nethack --showpaths
   list expected locations for various files and directories, then exit;

doc/nethack.6

@@ -123,8 +123,10 @@ Also
 [
 .BR \-\-showpaths
 ]
+.\" force line wrap now rather than have that happen after the opening brace
+.br
 [
-.BR \-\-version [ :copy ]
+.BR \-\-version [ :copy | :dump | :show ]
 ]
 .ad
 .hy 14
@@ -367,17 +369,27 @@ that many top scores.
 Combining names with role or race or both will report entries which match
 any of those rather than just the ones which match all.
 .PP
-.B \-\-version
+.\" avoid hyphenating "version" in this paragraph (and beyond; don't care)
-can be used to cause NetHack to show the version information it
+.hw version
-was compiled with, then exit.
+.BR \-\-version " or " \-\-version:show
-That will include the
+can be used to cause NetHack to show the version number, the date and
-.I git
+time that the program was built from its source code, and possibly
-commit hash if the information was available when the game was compiled.
+some auxiliary information about that source code, then exit.
-On some platforms, such as Windows and macOS, a variation
+The optional auxiliary information is \fIgit\fP
-.B \-\-version:copy
+commit hash (reflecting the source code's most recent modification when
+extracted from the \fIgit\fP version control system, if that is in use)
+if available when the program was built.
+On some platforms such as Windows and macOS, a variation,
+.BR \-\-version:copy ,
 can be used to cause NetHack to show the version information, then exit,
-while also leaving a copy of the version information in the paste buffer
+while also leaving a copy of that information in the paste buffer
 or clipboard for potential insertion into things like bug reports.
+On any platform,
+.B \-\-version:dump
+can be used to show most of the data used when checking whether a save
+file or bones file is compatible with the program.
+The program will display a line containing five numbers expressed in
+hexadecimal, then exit.
 .PP
 .B \-\-showpaths
 can be used to cause NetHack to show where it is expecting

include/extern.h

@@ -3387,6 +3387,7 @@ extern unsigned long get_feature_notice_ver(char *) NO_NNARGS;
 extern unsigned long get_current_feature_ver(void);
 extern const char *copyright_banner_line(int) NONNULL;
 extern void early_version_info(boolean);
+extern void dump_version_info(void);
 
 /* ### video.c ### */
 
@@ -3791,3 +3792,5 @@ extern void port_insert_pastebuf(char *);
 #endif /* !MAKEDEFS_C && !MDLIB_C */
 
 #endif /* EXTERN_H */
+
+/*extern.h*/

src/allmain.c

@@ -936,7 +936,7 @@ argcheck(int argc, char *argv[], enum earlyarg e_arg)
             break;
     }
     if (idx >= SIZE(earlyopts) || argc < 1)
-        return FALSE;
+        return 0;
 
     for (i = 0; i < argc; ++i) {
         if (argv[i][0] != '-')
@@ -975,13 +975,21 @@ argcheck(int argc, char *argv[], enum earlyarg e_arg)
                        than  next major version */
                 if (match_optname(extended_opt, "paste", 5, FALSE)) {
                     insert_into_pastebuf = TRUE;
-                } else if(match_optname(extended_opt, "copy", 4, FALSE)) {
+                } else if (match_optname(extended_opt, "copy", 4, FALSE)) {
                     insert_into_pastebuf = TRUE;
-                } else {
+                } else if (match_optname(extended_opt, "dump", 4, FALSE)) {
-                    raw_printf(
+                    /* version number plus enabled features and sanity
-                   "-%sversion can only be extended with -%sversion:copy.\n",
+                       values that the program compares against the same
+                       thing recorded in save and bones files to check
+                       whether they're being used compatibly */
+                    dump_version_info();
+                    return 2; /* done */
+                } else if (!match_optname(extended_opt, "show", 4, FALSE)) {
+                    raw_printf("-%sversion can only be extended with"
+                               " -%sversion:copy or :dump or :show.\n",
                                dashdash, dashdash);
-                    return TRUE;
+                    /* exit after we've reported bad command line argument */
+                    return 2;
                 }
             }
             early_version_info(insert_into_pastebuf);
@@ -1016,7 +1024,7 @@ argcheck(int argc, char *argv[], enum earlyarg e_arg)
             break;
         }
     };
-    return FALSE;
+    return 0;
 }
 
 /*

src/version.c

@@ -485,4 +485,26 @@ copyright_banner_line(int indx)
     return "";
 }
 
+/* called by argcheck(allmain.c) from early_options(sys/xxx/xxxmain.c) */
+void
+dump_version_info(void)
+{
+    char buf[BUFSZ];
+    const char *hname = gh.hname ? gh.hname : "nethack";
+
+    if (strlen(hname) > 33)
+        hname = eos(nhStr(hname)) - 33; /* discard const for eos() */
+    runtime_info_init();
+    Snprintf(buf, sizeof buf, "%-12.33s %08lx %08lx %08lx %08lx %08lx",
+             hname,
+             nomakedefs.version_number,
+             (nomakedefs.version_features & ~nomakedefs.ignored_features),
+             nomakedefs.version_sanity1,
+             nomakedefs.version_sanity2,
+             nomakedefs.version_sanity3);
+    raw_print(buf);
+    release_runtime_info();
+    return;
+}
+
 /*version.c*/