Element next-line scopes may nest, so man_breakscope() may have to

break multiple element next-line scopes at the same time, similar to
what man_descope() already does for unconditional rewinding.

This fixes an assertion failure that tb@ found with afl(1), caused
by .SH .I .I .BI and similar sequences of macros without arguments.

4 files changed, 41 insertions, 3 deletions

diff --git a/regress/usr.bin/mandoc/man/B/Makefile b/regress/usr.bin/mandoc/man/B/Makefile
index ac010e1ba62..a3ac6257dd4 100644
--- a/regress/usr.bin/mandoc/man/B/Makefile
+++ b/regress/usr.bin/mandoc/man/B/Makefile
@@ -1,7 +1,7 @@
-# $OpenBSD: Makefile,v 1.2 2017/06/03 15:54:09 schwarze Exp $
+# $OpenBSD: Makefile,v 1.3 2022/04/28 10:17:38 schwarze Exp $
 
-REGRESS_TARGETS	= args blank
-LINT_TARGETS	= args blank
+REGRESS_TARGETS	= args blank nest
+LINT_TARGETS	= args blank nest
 
 # groff-1.22.3 defect:
 # - A blank line in next line scope causes a blank line.
diff --git a/regress/usr.bin/mandoc/man/B/nest.in b/regress/usr.bin/mandoc/man/B/nest.in
new file mode 100644
index 00000000000..3edf2077394
--- /dev/null
+++ b/regress/usr.bin/mandoc/man/B/nest.in
@@ -0,0 +1,20 @@
+.\" $OpenBSD: nest.in,v 1.1 2022/04/28 10:17:38 schwarze Exp $
+.TH B-ARGS 1 "April 28, 2022"
+.SH NAME
+B-nest \- nested next-line scopes
+.SH DESCRIPTION
+initial text
+.B
+.SM
+bold text
+back to roman
+.B
+.SM
+.IR italic roman
+.B
+.SM
+.SH
+.B
+.B
+.RI section header
+final text
diff --git a/regress/usr.bin/mandoc/man/B/nest.out_ascii b/regress/usr.bin/mandoc/man/B/nest.out_ascii
new file mode 100644
index 00000000000..82ae6a7201b
--- /dev/null
+++ b/regress/usr.bin/mandoc/man/B/nest.out_ascii
@@ -0,0 +1,12 @@
+B-ARGS(1)                   General Commands Manual                  B-ARGS(1)
+
+NNAAMMEE
+       B-nest - nested next-line scopes
+
+DDEESSCCRRIIPPTTIIOONN
+       initial text bboolldd tteexxtt back to roman _i_t_a_l_i_croman
+
+section_h_e_a_d_e_r
+       final text
+
+OpenBSD                         April 28, 2022                       B-ARGS(1)
diff --git a/regress/usr.bin/mandoc/man/B/nest.out_lint b/regress/usr.bin/mandoc/man/B/nest.out_lint
new file mode 100644
index 00000000000..dd6ba7bd78b
--- /dev/null
+++ b/regress/usr.bin/mandoc/man/B/nest.out_lint
@@ -0,0 +1,6 @@
+mandoc: nest.in:12:2: WARNING: line scope broken: IR breaks SM
+mandoc: nest.in:11:2: WARNING: line scope broken: IR breaks B
+mandoc: nest.in:15:2: WARNING: line scope broken: SH breaks SM
+mandoc: nest.in:14:2: WARNING: line scope broken: SH breaks B
+mandoc: nest.in:18:2: WARNING: line scope broken: RI breaks B
+mandoc: nest.in:17:2: WARNING: line scope broken: RI breaks B