Rename mandoc_getarg() to roff_getarg() and pass it the roff parser

struct as an argument such that after copy-in, it can call roff_expand()
once again, which used to be called roff_res() before this.  This
fixes a subtle low-level roff(7) parsing bug reported by Fabio
Scotoni <fabio at esse dot ch> in the 4.4BSD-Lite2 mdoc.samples(7)
manual page, because that page used an escaped escape sequence in
a macro argument.

To expand escaped escape sequences in quoted mdoc(7) arguments, too,
stop bypassing the call to roff_getarg() in mdoc_argv.c, function args()
for this case.  This does not solve the case of escaped escape sequences
in quoted .Bl -column phrases yet.

Because roff_expand() can make the string longer, roff_getarg() can no
longer operate in-place but needs to malloc(3) the returned string.
In the high-level parsers, free(3) that string after processing it.

4 files changed, 61 insertions, 2 deletions

diff --git a/regress/usr.bin/mandoc/mdoc/Bl/Makefile b/regress/usr.bin/mandoc/mdoc/Bl/Makefile
index deda0bf7381..8fde5d9e07e 100644
--- a/regress/usr.bin/mandoc/mdoc/Bl/Makefile
+++ b/regress/usr.bin/mandoc/mdoc/Bl/Makefile
@@ -1,8 +1,8 @@
-# $OpenBSD: Makefile,v 1.39 2017/07/16 17:53:29 schwarze Exp $
+# $OpenBSD: Makefile,v 1.40 2018/12/21 16:58:49 schwarze Exp $
 
 REGRESS_TARGETS  = item inset diag ohang bullet dash enum hang tag
 REGRESS_TARGETS += column column_nogroff colNoIt
-REGRESS_TARGETS += extend nested offset secstart
+REGRESS_TARGETS += esc extend nested offset secstart
 
 REGRESS_TARGETS += notype multitype badargs
 REGRESS_TARGETS += empty noIt emptyhead emptytag emptyitem multitag
diff --git a/regress/usr.bin/mandoc/mdoc/Bl/esc.in b/regress/usr.bin/mandoc/mdoc/Bl/esc.in
new file mode 100644
index 00000000000..343ccc7de94
--- /dev/null
+++ b/regress/usr.bin/mandoc/mdoc/Bl/esc.in
@@ -0,0 +1,19 @@
+.\" $OpenBSD: esc.in,v 1.1 2018/12/21 16:58:49 schwarze Exp $
+.Dd $Mdocdate: December 21 2018 $
+.Dt BL-ESC 1
+.Os
+.Sh NAME
+.Nm Bl-esc
+.Nd escape sequences in full block macro heads
+.Sh DESCRIPTION
+.ds a \(at
+.Bl -tag -width 2n
+.It \*a
+unquoted unescaped
+.It "\*a"
+quoted unescaped
+.It \\*a
+unquoted escaped
+.It "\\*a"
+quoted escaped
+.El
diff --git a/regress/usr.bin/mandoc/mdoc/Bl/esc.out_ascii b/regress/usr.bin/mandoc/mdoc/Bl/esc.out_ascii
new file mode 100644
index 00000000000..e73c929f5b0
--- /dev/null
+++ b/regress/usr.bin/mandoc/mdoc/Bl/esc.out_ascii
@@ -0,0 +1,15 @@
+BL-ESC(1)                   General Commands Manual                  BL-ESC(1)
+
+NNAAMMEE
+     BBll--eesscc - escape sequences in full block macro heads
+
+DDEESSCCRRIIPPTTIIOONN
+     @   unquoted unescaped
+
+     @   quoted unescaped
+
+     @   unquoted escaped
+
+     @   quoted escaped
+
+OpenBSD                        December 21, 2018                       OpenBSD
diff --git a/regress/usr.bin/mandoc/mdoc/Bl/esc.out_markdown b/regress/usr.bin/mandoc/mdoc/Bl/esc.out_markdown
new file mode 100644
index 00000000000..780a61b8f84
--- /dev/null
+++ b/regress/usr.bin/mandoc/mdoc/Bl/esc.out_markdown
@@ -0,0 +1,25 @@
+BL-ESC(1) - General Commands Manual
+
+# NAME
+
+**Bl-esc** - escape sequences in full block macro heads
+
+# DESCRIPTION
+
+@
+
+> unquoted unescaped
+
+@
+
+> quoted unescaped
+
+@
+
+> unquoted escaped
+
+@
+
+> quoted escaped
+
+OpenBSD - December 21, 2018