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, 50 insertions, 2 deletions

diff --git a/regress/mdoc/Fd/Makefile b/regress/mdoc/Fd/Makefile
index 7cd78c65..39b07f1d 100644
--- a/regress/mdoc/Fd/Makefile
+++ b/regress/mdoc/Fd/Makefile
@@ -1,6 +1,6 @@
-# $OpenBSD: Makefile,v 1.3 2015/02/06 03:31:11 schwarze Exp $
+# $OpenBSD: Makefile,v 1.7 2018/12/21 16:58:49 schwarze Exp $
 
-REGRESS_TARGETS	 = break empty eos font
+REGRESS_TARGETS	 = arg break empty eos font
 LINT_TARGETS	 = empty
 SKIP_TMAN	 = eos
 
diff --git a/regress/mdoc/Fd/arg.in b/regress/mdoc/Fd/arg.in
new file mode 100644
index 00000000..659d03c9
--- /dev/null
+++ b/regress/mdoc/Fd/arg.in
@@ -0,0 +1,16 @@
+.\" $OpenBSD: arg.in,v 1.1 2018/12/21 16:58:49 schwarze Exp $
+.Dd $Mdocdate: December 21 2018 $
+.Dt FD-ARG 2
+.Os
+.Sh NAME
+.Nm Fd-arg
+.Nd escape sequences in the arguments of in-line EOL macros
+.Sh DESCRIPTION
+.ds s \(sh
+.Fd \*sunquoted unescaped
+.Pp
+.Fd "\*squoted" unescaped
+.Pp
+.Fd \\*sunquoted escaped
+.Pp
+.Fd "\\*squoted" escaped
diff --git a/regress/mdoc/Fd/arg.out_ascii b/regress/mdoc/Fd/arg.out_ascii
new file mode 100644
index 00000000..42836e61
--- /dev/null
+++ b/regress/mdoc/Fd/arg.out_ascii
@@ -0,0 +1,15 @@
+FD-ARG(2)                     System Calls Manual                    FD-ARG(2)
+
+NNAAMMEE
+     FFdd--aarrgg - escape sequences in the arguments of in-line EOL macros
+
+DDEESSCCRRIIPPTTIIOONN
+     ##uunnqquuootteedd uunneessccaappeedd
+
+     ##qquuootteedd uunneessccaappeedd
+
+     ##uunnqquuootteedd eessccaappeedd
+
+     ##qquuootteedd eessccaappeedd
+
+OpenBSD                        December 21, 2018                       OpenBSD
diff --git a/regress/mdoc/Fd/arg.out_markdown b/regress/mdoc/Fd/arg.out_markdown
new file mode 100644
index 00000000..14dba6fc
--- /dev/null
+++ b/regress/mdoc/Fd/arg.out_markdown
@@ -0,0 +1,17 @@
+FD-ARG(2) - System Calls Manual
+
+# NAME
+
+**Fd-arg** - escape sequences in the arguments of in-line EOL macros
+
+# DESCRIPTION
+
+**#unquoted unescaped**
+
+**#quoted unescaped**
+
+**#unquoted escaped**
+
+**#quoted escaped**
+
+OpenBSD - December 21, 2018