musl libc build, rather than glibc

We've had reports of a couple of issues building against musl libc.

Issues reported:
  - build procedures utilize cat for Guidebook-creation, and cat
    is deprecated in distros that use musl libc.

  - some of the CRASHREPORT code is using library functions that
    are not available in the musl libc environment. The reported
    functions were backtrace() and backtrace_symbols(), which use
    header file /usr/include/execinfo.h.

So we'll try to accommodate this. Since we don't have a means of
autodetecting the musl libc situation during the build (as of yet), the
builder will have to specify 'make musl=1' on the make command line.

Specifying 'musl=1' on the make command line will:
1. ensure that NOCRASHREPORT gets defined in the C preprocessor.
2. set COLCMD to be '../util/stripbs' instead of 'col -bx'.

Closes #1393

sys/unix/Makefile.doc

@@ -11,6 +11,8 @@ NHSROOT=..
 
 MAKEDEFS = ../util/makedefs
 
+#STRIPBS ?= ../util/stripbs
+
 # Which version do we want to build?  (XXX These are not used anywhere.)
 GUIDEBOOK = Guidebook		# regular ASCII file
 #GUIDEBOOK = Guidebook.ps	# PostScript file
@@ -21,8 +23,9 @@ GUIDEBOOK = Guidebook		# regular ASCII file
 # recognize the option.  Sigh.
 #
 # col is unnecessary, but harmless, with groff.  See grotty(1).
-COLCMD = col -bx
-#COLCMD = col -b
+COLCMD ?= col -bx
+#COLCMD ?= col -b
+#COLCMD ?= $(STRIPBS)
 
 # The command to use to generate a PostScript file
 # PSCMD = ditroff | psdit
@@ -59,8 +62,8 @@ ONEPAGE_PREFORMAT = cat Gbk-1pg-pfx.mn $(GUIDEBOOK_MN) Gbk-1pg-sfx.mn \
 	| $(NHGREP) | tbl tmac.n -
 
 # the basic guidebook
-Guidebook	: $(GUIDEBOOK_MN) tmac.n tmac.nh $(NEEDMAKEDEFS)
-	$(GUIDECMD) > Guidebook
+Guidebook	: $(GUIDEBOOK_MN) tmac.n tmac.nh $(NEEDMAKEDEFS) $(STRIPBS)
+	-$(GUIDECMD) > Guidebook
 
 # Fancier output for those with ditroff, psdit and a PostScript printer.
 # Could be converted to Guidebook.pdf if tool(s) for that are available.
@@ -80,7 +83,10 @@ Guidebook.dvi	: $(GUIDEBOOK_TEX)
 # (note: 'make makedefs', not 'make $(MAKEDEFS)')
 $(MAKEDEFS)	: ../util/makedefs.c ../include/config.h ../src/mdlib.c \
 		  ../util/mdgrep.h
-	( cd ../util ; make makedefs )
+	( cd .. ; make makedefs )
+
+../util/stripbx: ../util/stripbs.c
+	( cd .. ; $(MAKE) stripbs )
 
 GAME	= nethack
 MANDIR	?= /usr/man/man6

sys/unix/Makefile.top

@@ -416,6 +416,12 @@ fetch-docs:
 	  shift; \
 	done
 
+makedefs:
+	( cd util ; $(MAKE) makedefs )
+
+stripbs:
+	( cd util ; $(MAKE) stripbs )
+
 # 'make update' can be used to install a revised version after making
 # customizations or such.  Unlike 'make install', it doesn't delete everything
 # from the target directory to have a clean start.

sys/unix/Makefile.utl

@@ -293,6 +293,11 @@ dlb:	$(DLBOBJS) $(HACKLIB)
 dlb_main.o: dlb_main.c $(CONFIG_H) ../include/dlb.h
 	$(CC) $(CFLAGS) $(CSTD) -c dlb_main.c -o $@
 
+stripbs: stripbs.o
+	$(CC) $(LFLAGS) -o stripbs stripbs.o
+
+stripbs.o: stripbs.c
+	$(CC) $(CFLAGS) -c stripbs.c
 
 #	dependencies for tile utilities
 #

sys/unix/hints/include/multiw-2.370

@@ -194,6 +194,20 @@ CPLUSPLUS_NEEDED = 1
 endif
 endif
 
+ifeq "$(musl)" "1"
+MUSL=1
+endif
+ifeq "$(MUSL)" "1"
+ifneq "$(NOCRASHREPORT)" "1"
+NOCRASHREPORT=1
+endif
+WINCFLAGS += -DMUSL_LIBC
+# use this instead of col -bx
+COLCMD = ../util/stripbs
+else
+WINCFLAGS += -DGNU_LIBC
+endif
+
 ifeq "$(NOCRASHREPORT)" "1"
 WINCFLAGS += -DNOCRASHREPORT
 endif

util/.gitignore

@@ -11,6 +11,7 @@ lev_comp
 dlb
 dlb_main
 recover
+stripbs
 tilemap
 tileedit
 tile2x11

util/stripbs.c

@@ -0,0 +1,42 @@
+/* NetHack 3.7  stripbs.c                                         */
+/* Copyright (c) Michael Allison, 2025.                                */
+/* NetHack may be freely redistributed.  See license for details. */
+
+/*
+ * a simple filter to strip character-backspace-character
+ * from stdin and write the results to stdout.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+int main(int argc, char *argv[])
+{
+    int stop = 0, trouble = 0;
+    char buf[2];
+    char *cp = &buf[0], *prev = &buf[1];
+
+    *prev = 0;
+    while (!stop) {
+        if ((fread(buf, 1, 1, stdin)) > 0) {
+            if (*cp == 8) {
+		*prev = 0;
+	    } else {
+		if (*prev)
+                    fputc(*prev, stdout);
+		*prev = *cp;
+	    }
+        } else {
+	    if (errno != EOF)
+                trouble = 1;
+	    if (*prev)
+                fputc(*prev, stdout);
+            stop = 1;
+        }
+    }
+    fflush(stdout);
+    fclose(stdout);
+    return trouble ? EXIT_FAILURE : EXIT_SUCCESS;
+}