[groff] 12/13: [tbl]: Refactor table entry content validation.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit be0488976d91cd18314ca68e285c8616ad7ce2a3
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Sun Oct 6 12:40:15 2024 -0500

    [tbl]: Refactor table entry content validation.
    
    * src/preproc/tbl/table.cpp (table::add_entry): Refactor match attempts
      for `\R` and `\z` in table entries to use new `find()` member function
      of `string` class.
    
    $ cat -n ./bad-escapes-in-tables.roff
         1  This is my table.
         2  .sp
         3  .TS
         4  L.
         5  foo \" comment
         6  bar\# another comment
         7  baz\!qux
         8  .\" This should produce no diagnostic.
         9  T{
        10  This is fine. \" fingers crossed\! [sic]
        11  T}
        12  \Rx
        13  T{
        14  \Rx \" this is bad trouble
        15  T}
        16  .\" as is the next line
        17  qux\z
        18  .TE
    $ ./build/tbl ./bad-escapes-in-tables.roff >/dev/null
    ./build/tbl:./bad-escapes-in-tables.roff:5: warning: table entry contains 
comment escape sequence '\"'
    ./build/tbl:./bad-escapes-in-tables.roff:5: warning: table entry contains 
comment escape sequence '\#'
    ./build/tbl:./bad-escapes-in-tables.roff:7: warning: table entry contains 
transparent throughput escape sequence '\!'
    ./build/tbl:./bad-escapes-in-tables.roff:14: warning: table entry contains 
comment escape sequence '\"'
    ./build/tbl:./bad-escapes-in-tables.roff:14: warning: table entry contains 
comment escape sequence '\#'
    ./build/tbl:./bad-escapes-in-tables.roff:14: error: repeating a glyph with 
'\R' is not allowed in a text block
    ./build/tbl:./bad-escapes-in-tables.roff:17: error: table entry ends with 
zero-motion escape sequence '\z'
---
 ChangeLog                 |  6 ++++++
 src/preproc/tbl/table.cpp | 12 ++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index f7a91de07..7129aba6e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2024-10-06  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+       * src/preproc/tbl/table.cpp (table::add_entry): Refactor match
+       attempts for `\R` and `\z` in table entries to use new `find()`
+       member function of `string` class.
+
 2024-10-06  G. Branden Robinson <g.branden.robinson@gmail.com>
 
        * src/preproc/tbl/table.cpp (table::add_entry): Refactor to
diff --git a/src/preproc/tbl/table.cpp b/src/preproc/tbl/table.cpp
index d0a19beca..3c4bd5a85 100644
--- a/src/preproc/tbl/table.cpp
+++ b/src/preproc/tbl/table.cpp
@@ -1558,17 +1558,17 @@ void table::add_entry(int r, int c, const string &str,
       warning_with_file_and_line(fn, ln, "table entry contains"
                                 " transparent throughput escape"
                                 " sequence '\\!'");
-    string last_two_chars = str.substring((len - 2), 2);
-    if ("\\z" == last_two_chars)
+    // An incomplete \z sequence at the entry's end causes problems.
+    if (str.find("\\z") == (len - 2)) // max valid index is (len - 1)
       error_with_file_and_line(fn, ln, "table entry ends with"
                               " zero-motion escape sequence '\\z'");
   }
   char *s = str.extract();
-  if (str.search('\n') >= 0) {
+  if (str.search('\n') != -1) { // if it's a text block
     bool was_changed = false;
-    for (int i = 0; s[i] != '\0'; i++)
-      if ((i > 0) && (s[(i - 1)] == '\\') && (s[i] == 'R')) {
-       s[i] = '&';
+    int repeatpos = str.find("\\R");
+    if (repeatpos != -1) {
+       s[++repeatpos] = '&';
        was_changed = true;
       }
     if (was_changed)