Implement the roff(7) .shift and .return requests,

for example used by groff_hdtbl(7) and groff_mom(7).

Also correctly interpolate arguments during nested macro execution
even after .shift and .return, implemented using a stack of argument
arrays.

Note that only read.c, but not roff.c can detect the end of a macro
execution, and the existence of .shift implies that arguments cannot
be interpolated up front, so unfortunately, this includes a partial
revert of roff.c rev. 1.337, moving argument interpolation back into
the function roff_res().

1 files changed, 22 insertions, 0 deletions

diff --git a/mandoc.1 b/mandoc.1
index 6534e43e..0a49de0e 100644
--- a/mandoc.1
+++ b/mandoc.1
@@ -1807,6 +1807,13 @@ or
 macro.
 It may be mistyped or unsupported.
 The request or macro is discarded including its arguments.
+.It Sy "skipping request outside macro"
+.Pq roff
+A
+.Ic shift
+or
+.Ic return
+request occurs outside any macro definition and has no effect.
 .It Sy "skipping insecure request"
 .Pq roff
 An input file attempted to run a shell command
@@ -1916,6 +1923,14 @@ When parsing for a request or a user-defined macro name to be called,
 only the escape sequence is discarded.
 The characters preceding it are used as the request or macro name,
 the characters following it are used as the arguments to the request or macro.
+.It Sy "using macro argument outside macro"
+.Pq roff
+The escape sequence \e$ occurs outside any macro definition
+and expands to the empty string.
+.It Sy "argument number is not numeric"
+.Pq roff
+The argument of the escape sequence \e$ is not a digit;
+the escape sequence expands to the empty string.
 .It Sy "NOT IMPLEMENTED: Bd -file"
 .Pq mdoc
 For security reasons, the
@@ -1978,6 +1993,13 @@ or
 .Ic \&gsize
 statement has a non-numeric or negative argument or no argument at all.
 The invalid request or statement is ignored.
+.It Sy "excessive shift"
+.Pq roff
+The argument of a
+.Ic shift
+request is larger than the number of arguments of the macro that is
+currently being executed.
+All macro arguments are deleted and \en(.$ is set to zero.
 .It Sy "NOT IMPLEMENTED: .so with absolute path or \(dq..\(dq"
 .Pq roff
 For security reasons,