master 7c26501175f: regex.c (mutually_exclusive_aux) <wordbound>: Remove optimization

[Stefan Monnier]

branch: master
commit 7c26501175f7dc657c677c151d49d04291ea67e7
Author: Stefan Monnier <monnier@iro.umontreal.ca>
Commit: Stefan Monnier <monnier@iro.umontreal.ca>

    regex.c (mutually_exclusive_aux) <wordbound>: Remove optimization
    
    Another case that was too optimistic.  Better use \> or \< rather
    than \b if you want your regexp to be handled efficiently.
    
    * src/regex-emacs.c (mutually_exclusive_aux) <wordbound>: Cancel 
optimization.
    * test/src/regex-emacs-tests.el (regexp-tests-backtrack-optimization):
    New test.
---
 src/regex-emacs.c             | 17 +++++++++++++++--
 test/src/regex-emacs-tests.el |  1 +
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/regex-emacs.c b/src/regex-emacs.c
index ae82dd63917..ad140908609 100644
--- a/src/regex-emacs.c
+++ b/src/regex-emacs.c
@@ -3874,9 +3874,22 @@ mutually_exclusive_aux (struct re_pattern_buffer *bufp, 
re_char *p1,
       return ((re_opcode_t) *p1 == notsyntaxspec && p1[1] == p2[1]);
 
     case wordbound:
+      /* FIXME: This optimization seems correct after the first iteration
+         of the loop, but not for the very first :-(
+         IOW we'd need to pull out the first iteration and do:
+
+            syntaxspec w
+            on_failure_keep_string_jump end
+          loop:
+            syntaxspec w
+            goto loop
+          end:
+            wordbound
+
       return (((re_opcode_t) *p1 == notsyntaxspec
-              || (re_opcode_t) *p1 == syntaxspec)
-             && p1[1] == Sword);
+               || (re_opcode_t) *p1 == syntaxspec)
+              && p1[1] == Sword);  */
+      return false;
 
     case categoryspec:
       return ((re_opcode_t) *p1 == notcategoryspec && p1[1] == p2[1]);
diff --git a/test/src/regex-emacs-tests.el b/test/src/regex-emacs-tests.el
index d78f70ba409..621e4dbe2c0 100644
--- a/test/src/regex-emacs-tests.el
+++ b/test/src/regex-emacs-tests.el
@@ -907,6 +907,7 @@ This evaluates the TESTS test cases from glibc."
     ;; Regression check for overly optimistic optimization.
     (should (eq 0 (string-match "\\(ca*\\|ab\\)+d" "cabd")))
     (should (string-match "\\(aa*\\|b\\)*c" "ababc"))
+    (should (string-match " \\sw*\\bfoo" " foo"))
     ))
 
 (ert-deftest regexp-tests-zero-width-assertion-repetition ()