[groff] 08/09: src/roff/troff/env.cpp: Avoid infinite loop.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit bcdf2f4c7c28328c711c6a7ac2ea17f2ecd5cdd4
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Wed Oct 21 00:29:24 2020 +1100

    src/roff/troff/env.cpp: Avoid infinite loop.
    
    * src/roff/troff/env.cpp (environment::possibly_break_line): Emit break
      warning and return if the output width is not positive.  The code
      assumes that it will be and loops infinitely if it isn't.  I _think_
      this is because we're not able to get width data for (some?) CJK
      glyphs.  Based on a patch by Osamu Sayama.
    
    Fixes <https://savannah.gnu.org/bugs/index.php?44018>.
---
 ChangeLog              | 15 +++++++++++++++
 src/roff/troff/env.cpp | 14 ++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index ce0b7ea..d9ccebc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,20 @@
 2020-10-20  G. Branden Robinson <g.branden.robinson@gmail.com>
 
+       * src/roff/troff/env.cpp (environment::possibly_break_line):
+       Emit break warning and return if the output width is not
+       positive.  The code assumes that it will be and loops infinitely
+       if it isn't.  I _think_ this is because we're not able to get
+       width data for (some?) CJK glyphs.  Based on a patch by Osamu
+       Sayama.
+
+       * src/roff/groff/tests/\
+       do_not_loop_infinitely_when_breaking_cjk.sh: Test it.
+       * src/roff/groff/groff.am: Run test.
+
+       Fixes <https://savannah.gnu.org/bugs/index.php?44018>.
+
+2020-10-20  G. Branden Robinson <g.branden.robinson@gmail.com>
+
        * src/preproc/tbl/table.cpp (table::init_output): Save the value
        of \n[.tabs] when starting a table.  In the reset macro, restore
        the saved value.
diff --git a/src/roff/troff/env.cpp b/src/roff/troff/env.cpp
index 9cbc130..cb6b1b1 100644
--- a/src/roff/troff/env.cpp
+++ b/src/roff/troff/env.cpp
@@ -2142,6 +2142,14 @@ void environment::possibly_break_line(int start_here, 
int forced)
     }
     distribute_space(pre, bp->nspaces, extra_space_width);
     hunits output_width = bp->width + extra_space_width;
+    // This should become an assert() when we can get reliable width
+    // data from CJK glyphs.  See Savannah #44018.
+    if (output_width <= 0) {
+      double output_width_in_ems = output_width.to_units();
+      output_warning(WARN_BREAK, "line has non-positive width %1m",
+                    output_width_in_ems);
+      return;
+    }
     input_line_start -= output_width;
     if (bp->hyphenated)
       hyphen_line_count++;
@@ -4107,3 +4115,9 @@ void init_hyphen_requests()
   init_request("hpfa", hyphenation_patterns_file_append);
   number_reg_dictionary.define(".hla", new hyphenation_language_reg);
 }
+
+// Local Variables:
+// fill-column: 72
+// mode: C++
+// End:
+// vim: set cindent noexpandtab shiftwidth=2 textwidth=72: