dfa: do not warn about \] and \}

* lib/dfa.c (lex): Do not warn about \] and \}, since they’re
surely universally supported even though POSIX says their
interpretation is undefined.

2 files changed, 7 insertions, 1 deletions

diff --git a/lib/dfa.c b/lib/dfa.c
index bd4c5f0582..4f8367af3f 100644
--- a/lib/dfa.c
+++ b/lib/dfa.c
@@ -1563,6 +1563,8 @@ lex (struct dfa *dfa)
                 }
               dfawarn (msg);
             }
+          FALLTHROUGH;
+        case ']': case '}':
         normal_char:
           dfa->lex.laststart = false;
           /* For multibyte character sets, folding is done in atom.  Always
diff --git a/lib/dfa.h b/lib/dfa.h
index 91ec1d809f..043f0e9717 100644
--- a/lib/dfa.h
+++ b/lib/dfa.h
@@ -79,7 +79,11 @@ enum
        merely a warning.  */
     DFA_CONFUSING_BRACKETS_ERROR = 1 << 2,
 
-    /* Warn about stray backslashes before ordinary characters.  */
+    /* Warn about stray backslashes before ordinary characters other
+       than ] and } which are special because even though POSIX
+       says \] and \} have undefined interpretation, platforms
+       reliably ignore those stray backlashes and warning about them
+       would likely cause more trouble than it's worth.  */
     DFA_STRAY_BACKSLASH_WARN = 1 << 3,
 
     /* Warn about * appearing out of context at the start of an