I am uploading a NMU to fix this.
diff -Nru intercal-0.30/buildaux/Makefile.in intercal-0.30/buildaux/Makefile.in
--- intercal-0.30/buildaux/Makefile.in 2023-05-18 15:11:21.000000000 +0200
+++ intercal-0.30/buildaux/Makefile.in 2015-04-02 18:30:18.582992990 +0200
@@ -1699,7 +1699,7 @@
chmod u+w $(top_srcdir)/pit
chmod u+w $(top_srcdir)/pit/lib
chmod u+w $(top_srcdir)/pit/tests
- make -f $(top_srcdir)/pit/Makefile ICK="./ick$(EXEEXT)" ICKOPTS="-b"
PIT=$(top_srcdir)/pit test
+ make -f $(top_srcdir)/pit/Makefile ICK="./ick$(EXEEXT) -b"
PIT=$(top_srcdir)/pit test
# Run the fuzztest
fuzz: ick$(EXEEXT) src/idiotism.oil $(top_srcdir)/etc/interfuzz.pl
diff -Nru intercal-0.30/debian/changelog intercal-0.30/debian/changelog
--- intercal-0.30/debian/changelog 2023-05-18 15:11:21.000000000 +0200
+++ intercal-0.30/debian/changelog 2023-05-18 15:01:42.000000000 +0200
@@ -1,3 +1,11 @@
+intercal (30:0.30-3.1) unstable; urgency=medium
+
+ * Non-maintainer upload.
+ * Fix build with gcc-10 (closes: #957366).
+ * Convert to source format 3.0 (quilt).
+
+ -- Bastian Germann <b...@debian.org> Thu, 18 May 2023 15:01:42 +0200
+
intercal (30:0.30-3) unstable; urgency=low
* Fix symlink for lib in examples (closes: #861502).
diff -Nru intercal-0.30/debian/patches/c-intercal-31.0-no-common.patch
intercal-0.30/debian/patches/c-intercal-31.0-no-common.patch
--- intercal-0.30/debian/patches/c-intercal-31.0-no-common.patch
1970-01-01 01:00:00.000000000 +0100
+++ intercal-0.30/debian/patches/c-intercal-31.0-no-common.patch
2023-05-18 14:55:02.000000000 +0200
@@ -0,0 +1,13 @@
+https://bugs.gentoo.org/711902
+
+--- intercal-0.31-orig/src/perpet.c
++++ intercal-0.31/src/perpet.c
+@@ -85,7 +85,7 @@
+ /* function created by yacc */
+ extern int yyparse(void);
+
+-int yydebug;
++extern int yydebug;
+
+ /* compilation options */
+ bool compile_only; /* just compile into C, don't run the linker */
diff -Nru intercal-0.30/debian/patches/debian.patch
intercal-0.30/debian/patches/debian.patch
--- intercal-0.30/debian/patches/debian.patch 1970-01-01 01:00:00.000000000
+0100
+++ intercal-0.30/debian/patches/debian.patch 2023-05-18 15:00:47.000000000
+0200
@@ -0,0 +1,30 @@
+--- intercal-0.30.orig/buildaux/Makefile.in
++++ intercal-0.30/buildaux/Makefile.in
+@@ -1699,7 +1699,7 @@ check-am: ick$(EXEEXT)
+ chmod u+w $(top_srcdir)/pit
+ chmod u+w $(top_srcdir)/pit/lib
+ chmod u+w $(top_srcdir)/pit/tests
+- make -f $(top_srcdir)/pit/Makefile ICK="./ick$(EXEEXT) -b"
PIT=$(top_srcdir)/pit test
++ make -f $(top_srcdir)/pit/Makefile ICK="./ick$(EXEEXT)" ICKOPTS="-b"
PIT=$(top_srcdir)/pit test
+
+ # Run the fuzztest
+ fuzz: ick$(EXEEXT) src/idiotism.oil $(top_srcdir)/etc/interfuzz.pl
+--- intercal-0.30.orig/doc/Makefile
++++ intercal-0.30/doc/Makefile
+@@ -34,14 +34,14 @@ original.ps: intercal.mm
+ -rm -f intercal.refs.qrf intercal.refs.tmp
+
+ intercal.txt: intercal.mm
+- groff -U -dc=y -Tascii -p -t -mm intercal.mm >/dev/null
++ groff -U -dc=y -Tascii -p -t -mm intercal.mm >intercal.refs.tmp
+ sed <intercal.refs.tmp -e '/hn \([0-9]*\)\.$$/s//hn \1/' >tmp.refs;
+ mv tmp.refs intercal.refs.tmp
+ GROFF_NO_SGR=1 groff -U -dc=y -Tascii -p -t -mm intercal.mm
>intercal.txt
+ -rm -f intercal.refs.qrf intercal.refs.tmp
+
+ original.txt: intercal.mm
+- groff -U -dc=n -Tascii -p -t -mm intercal.mm >/dev/null
++ groff -U -dc=n -Tascii -p -t -mm intercal.mm >intercal.refs.tmp
+ sed <intercal.refs.tmp -e '/hn \([0-9]*\)\.$$/s//hn \1/' >tmp.refs;
+ mv tmp.refs intercal.refs.tmp
+ GROFF_NO_SGR=1 groff -U -dc=n -Tascii -p -t -mm intercal.mm
>original.txt
diff -Nru intercal-0.30/debian/patches/series
intercal-0.30/debian/patches/series
--- intercal-0.30/debian/patches/series 1970-01-01 01:00:00.000000000 +0100
+++ intercal-0.30/debian/patches/series 2023-05-18 15:01:24.000000000 +0200
@@ -0,0 +1,2 @@
+debian.patch
+c-intercal-31.0-no-common.patch
diff -Nru intercal-0.30/debian/rules intercal-0.30/debian/rules
--- intercal-0.30/debian/rules 2023-05-18 15:11:21.000000000 +0200
+++ intercal-0.30/debian/rules 2023-05-18 15:01:42.000000000 +0200
@@ -1,5 +1,6 @@
#!/usr/bin/make -f
+export DEB_CFLAGS_MAINT_APPEND=-fno-toplevel-reorder
DPKG_EXPORT_BUILDFLAGS=1
include /usr/share/dpkg/buildflags.mk
diff -Nru intercal-0.30/debian/source/format intercal-0.30/debian/source/format
--- intercal-0.30/debian/source/format 1970-01-01 01:00:00.000000000 +0100
+++ intercal-0.30/debian/source/format 2023-05-18 14:59:32.000000000 +0200
@@ -0,0 +1 @@
+3.0 (quilt)
diff -Nru intercal-0.30/doc/Makefile intercal-0.30/doc/Makefile
--- intercal-0.30/doc/Makefile 2023-05-18 15:11:21.000000000 +0200
+++ intercal-0.30/doc/Makefile 2010-09-11 13:09:46.000000000 +0200
@@ -34,14 +34,14 @@
-rm -f intercal.refs.qrf intercal.refs.tmp
intercal.txt: intercal.mm
- groff -U -dc=y -Tascii -p -t -mm intercal.mm >intercal.refs.tmp
+ groff -U -dc=y -Tascii -p -t -mm intercal.mm >/dev/null
sed <intercal.refs.tmp -e '/hn \([0-9]*\)\.$$/s//hn \1/' >tmp.refs;
mv tmp.refs intercal.refs.tmp
GROFF_NO_SGR=1 groff -U -dc=y -Tascii -p -t -mm intercal.mm
>intercal.txt
-rm -f intercal.refs.qrf intercal.refs.tmp
original.txt: intercal.mm
- groff -U -dc=n -Tascii -p -t -mm intercal.mm >intercal.refs.tmp
+ groff -U -dc=n -Tascii -p -t -mm intercal.mm >/dev/null
sed <intercal.refs.tmp -e '/hn \([0-9]*\)\.$$/s//hn \1/' >tmp.refs;
mv tmp.refs intercal.refs.tmp
GROFF_NO_SGR=1 groff -U -dc=n -Tascii -p -t -mm intercal.mm
>original.txt
