[bug #66079] [troff] uninitialized local `s` potentially used in `token::add_to_zero_width_node_list()`

[G. Branden Robinson]

Follow-up Comment #6, bug #66079 (group groff):

Hi Lukas,

In your second patch, there is no use of an uninitialized value; nothing ever
dereferences `s`.  This is true even though it is later written to.

However, the variable needs to exist because the API demands a dead store
here, so I'm changing the function to significantly narrow the scope of this
all-but-unused local variable.

Here's the patched function:


   297  void environment::add_char(charinfo *ci)
   298  {
   299    node *gc_np = 0 /* nullptr */;
   300    if (line_interrupted)
   301      ;
   302    // don't allow fields in dummy environments
   303    else if (ci == field_delimiter_char && !dummy) {
   304      if (has_current_field)
   305        wrap_up_field();
   306      else
   307        start_field();
   308    }
   309    else if (has_current_field && ci == padding_indicator_char)
   310      add_padding();
   311    else if (current_tab != TAB_NONE) {
   312      if (tab_contents == 0 /* nullptr */)
   313        tab_contents = new line_start_node;
   314      if (ci != hyphen_indicator_char) {
   315        int s;
   316        tab_contents = tab_contents->add_char(ci, this, &tab_width, &s,
   317                                              &gc_np);
   318      }
   319      else
   320        tab_contents = tab_contents->add_discretionary_hyphen();
   321    }
   322    else {
   323      if (line == 0 /* nullptr */)
   324        start_line();
   325  #if 0
   326      fprintf(stderr, "current line is\n");
   327      line->dump_node_list();
   328  #endif
   329      if (ci != hyphen_indicator_char)
   330        line = line->add_char(ci, this, &width_total, &space_total,
&gc_np);
   331      else
   332        line = line->add_discretionary_hyphen();
   333    }
   334  #if 0
   335    fprintf(stderr, "now after we have added character the line is\n");
   336    line->dump_node_list();
   337  #endif
   338    if ((!suppress_push) && gc_np) {
   339      if (gc_np && (gc_np->state == 0 /* nullptr */)) {
   340        gc_np->state = construct_state(false);
   341        gc_np->push_state = get_diversion_state();
   342      }
   343      else if (line && (line->state == 0 /* nullptr */)) {
   344        line->state = construct_state(false);
   345        line->push_state = get_diversion_state();
   346      }
   347    }
   348  #if 0
   349    fprintf(stderr, "now we have possibly added the state the line
is\n");
   350    line->dump_node_list();
   351  #endif
   352  }


...and the patch itself.


diff --git a/src/roff/troff/env.cpp b/src/roff/troff/env.cpp
index c3990f040..fa86b0504 100644
--- a/src/roff/troff/env.cpp
+++ b/src/roff/troff/env.cpp
@@ -296,7 +296,6 @@ void leader_character()
 
 void environment::add_char(charinfo *ci)
 {
-  int s;
   node *gc_np = 0 /* nullptr */;
   if (line_interrupted)
     ;
@@ -312,8 +311,11 @@ void environment::add_char(charinfo *ci)
   else if (current_tab != TAB_NONE) {
     if (tab_contents == 0 /* nullptr */)
       tab_contents = new line_start_node;
-    if (ci != hyphen_indicator_char)
-      tab_contents = tab_contents->add_char(ci, this, &tab_width, &s,
&gc_np);
+    if (ci != hyphen_indicator_char) {
+      int s;
+      tab_contents = tab_contents->add_char(ci, this, &tab_width, &s,
+                                           &gc_np);
+    }
     else
       tab_contents = tab_contents->add_discretionary_hyphen();
   }


Thanks for the report.


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