[groff] 02/03: [troff]: Ignore out-of-range .ad argument.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit 62601add468b2eff56910173e339e3fa4490a3de
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Mon Jan 25 17:36:34 2021 +1100

    [troff]: Ignore out-of-range .ad argument.
    
    * src/roff/troff/env.cpp: Add ADJUST_MAX enumeration constant to record
      maximum valid numerical adjustment mode.
      (adjust): Verify numeric argument against ADJUST_MAX instead of
      numeric literal.  Ignore excessively large values instead of setting
      adjustment mode to "right".  Update warning diagnostic.
    
    This is a behavior change, albeit to how an invalid argument is
    interpreted.  What we call "AT&T troff" in our documentation is a
    reference to CSTR #54 in its 1992 revision, which we use as a
    specification because source code to the implementations was not freely
    available.  Because the above circumstance is out-of-spec, "AT&T troff"
    says nothing about it and offers no precedent.
    
    Given that, let's have a look at what other *roffs do.
    
    * V7 Unix troff ignored invalid adjustment modes of all kinds, falling
      off the end of a switch with no default case.
    * DWB, Plan 9, and Solaris troff make no changes to V7 Unix troff here.
    * Heirloom Doctools troff and Neatroff extend the range of valid numeric
      arguments to support paragraph-at-a-time formatting.
    * Neatroff furthermore supports an '.ad k' mode for support of
      keshideh/kadisha justification of cursive scripts.
    
    GNU troff's historical behavior here does not seem useful, and prepares
    users poorly for adjustment modes groff may support in the future.
---
 ChangeLog              |  8 ++++++++
 src/roff/troff/env.cpp | 18 +++++++++++-------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 8bc10cb..75f6ee3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2021-01-25  G. Branden Robinson <g.branden.robinson@gmail.com>
 
+       * src/roff/troff/env.cpp: Add ADJUST_MAX enumeration constant to
+       record maximum valid numerical adjustment mode.
+       (adjust): Verify numeric argument against ADJUST_MAX instead of
+       a numeric literal.  Ignore excessively large values instead of
+       setting adjustment mode to "right".  Update warning diagnostic.
+
+2021-01-25  G. Branden Robinson <g.branden.robinson@gmail.com>
+
        Add regression test for .ad and .na requests.
 
        * src/roff/groff/tests/adjustment_works.sh: Do it.
diff --git a/src/roff/troff/env.cpp b/src/roff/troff/env.cpp
index b86d7c6..83e2985 100644
--- a/src/roff/troff/env.cpp
+++ b/src/roff/troff/env.cpp
@@ -35,7 +35,12 @@ along with this program.  If not, see 
<http://www.gnu.org/licenses/>. */
 
 symbol default_family("T");
 
-enum { ADJUST_LEFT = 0, ADJUST_BOTH = 1, ADJUST_CENTER = 3, ADJUST_RIGHT = 5 };
+enum { ADJUST_LEFT = 0,
+  ADJUST_BOTH = 1,
+  ADJUST_CENTER = 3,
+  ADJUST_RIGHT = 5,
+  ADJUST_MAX = 5,
+};
 
 enum {
   // Not all combinations are valid; see hyphenate_request() below.
@@ -1297,8 +1302,8 @@ void space_size()
       curenv->space_size = n;
     if (has_arg() && get_integer(&n))
       if (n < 0)
-       warning(WARN_RANGE, "negative sentence space size ignored:"
-               " '%1'", n);
+       warning(WARN_RANGE, "negative sentence space size ignored: "
+               "'%1'", n);
       else
        curenv->sentence_space_size = n;
     else
@@ -2523,10 +2528,9 @@ void adjust()
       if (get_integer(&n)) {
        if (n < 0)
          warning(WARN_RANGE, "negative adjustment mode");
-       else if (n > 5) {
-         curenv->adjust_mode = 5;
-         warning(WARN_RANGE, "adjustment mode '%1' out of range", n);
-       }
+       else if (n > ADJUST_MAX)
+         warning(WARN_RANGE, "out-of-range adjustment mode ignored: "
+                 "%1", n);
        else
          curenv->adjust_mode = n;
       }