- Check before dereference. - Fix memory leak - Remove duplicate if statement. - Remove trailing spaces. Change-Id: I140a05c8f7006493dddae753aebfa5b4577c65ef Reviewed-on: https://plan9port-review.googlesource.com/1301 Reviewed-by: Neven Sajko <nsajko@gmail.com> Reviewed-by: Russ Cox <rsc@swtch.com>

Change-Id: I042d63ea62e2abd599bf9767acb3374bb39ddc7d Reviewed-on: https://plan9port-review.googlesource.com/1050 Reviewed-by: Minux Ma <minux@golang.org> Reviewed-by: Russ Cox <rsc@google.com>

This bug fix allows some pathological regular expressions to cause the regexp library to report a stack overflow (really a stack filling; safe) but it also fixes the behavior of some common regexps. It is too hard to satisfy both.

echo SYSSYSR1 | sed 's/SYS.+/sysr1/' was producing SYSsysr1 instead of sysr1. Bug was introduced during overflow cleanup earlier this year. Also bring regexec.c and rregexec.c into sync again. Also allocate large enough lists in the regexec2/rregexec2 case.