Bug#26977 exception handlers never hreturn

  - In some cases, flow control optimization implemented in sp::optimize
    removes hreturn instructions, causing SQL exception handlers to:
      * never return
      * execute wrong logic
  - This patch overrides default short cut optimization on hreturn instructions
    to avoid this problem.


mysql-test/r/sp-code.result:
  Added test case
mysql-test/t/sp-code.test:
  Added test case
sql/sp_head.cc:
  Override opt_mark to get correct execution paths without jump short cut 
  optimization.
sql/sp_head.h:
  Added override sp_instr_hreturn::opt_shortcut_jump so that jump short cuts aren't
  performed on hreturn instructions operating on handlers which are set to CONTINUE
  after interruption.

1 files changed, 113 insertions, 0 deletions

diff --git a/mysql-test/r/sp-code.result b/mysql-test/r/sp-code.result
index 9d86a6bc08d..219f3c9b37a 100644
--- a/mysql-test/r/sp-code.result
+++ b/mysql-test/r/sp-code.result
@@ -620,4 +620,117 @@ SHOW PROCEDURE CODE p1;
 Pos	Instruction
 0	stmt 2 "CREATE INDEX idx ON t1 (c1)"
 DROP PROCEDURE p1;
+drop table if exists t1;
+drop procedure if exists proc_26977_broken;
+drop procedure if exists proc_26977_works;
+create table t1(a int unique);
+create procedure proc_26977_broken(v int)
+begin
+declare i int default 5;
+declare continue handler for sqlexception
+begin
+select 'caught something';
+retry:
+while i > 0 do
+begin
+set i = i - 1;
+select 'looping', i;
+end;
+end while retry;
+end;
+select 'do something';
+insert into t1 values (v);
+select 'do something again';
+insert into t1 values (v);
+end//
+create procedure proc_26977_works(v int)
+begin
+declare i int default 5;
+declare continue handler for sqlexception
+begin
+select 'caught something';
+retry:
+while i > 0 do
+begin
+set i = i - 1;
+select 'looping', i;
+end;
+end while retry;
+select 'optimizer: keep hreturn';
+end;
+select 'do something';
+insert into t1 values (v);
+select 'do something again';
+insert into t1 values (v);
+end//
+show procedure code proc_26977_broken;
+Pos	Instruction
+0	set i@1 5
+1	hpush_jump 8 2 CONTINUE
+2	stmt 0 "select 'caught something'"
+3	jump_if_not 7(7) (i@1 > 0)
+4	set i@1 (i@1 - 1)
+5	stmt 0 "select 'looping', i"
+6	jump 3
+7	hreturn 2
+8	stmt 0 "select 'do something'"
+9	stmt 5 "insert into t1 values (v)"
+10	stmt 0 "select 'do something again'"
+11	stmt 5 "insert into t1 values (v)"
+12	hpop 1
+show procedure code proc_26977_works;
+Pos	Instruction
+0	set i@1 5
+1	hpush_jump 9 2 CONTINUE
+2	stmt 0 "select 'caught something'"
+3	jump_if_not 7(7) (i@1 > 0)
+4	set i@1 (i@1 - 1)
+5	stmt 0 "select 'looping', i"
+6	jump 3
+7	stmt 0 "select 'optimizer: keep hreturn'"
+8	hreturn 2
+9	stmt 0 "select 'do something'"
+10	stmt 5 "insert into t1 values (v)"
+11	stmt 0 "select 'do something again'"
+12	stmt 5 "insert into t1 values (v)"
+13	hpop 1
+call proc_26977_broken(1);
+do something
+do something
+do something again
+do something again
+caught something
+caught something
+looping	i
+looping	4
+looping	i
+looping	3
+looping	i
+looping	2
+looping	i
+looping	1
+looping	i
+looping	0
+call proc_26977_works(2);
+do something
+do something
+do something again
+do something again
+caught something
+caught something
+looping	i
+looping	4
+looping	i
+looping	3
+looping	i
+looping	2
+looping	i
+looping	1
+looping	i
+looping	0
+optimizer: keep hreturn
+optimizer: keep hreturn
+drop table t1;
+drop procedure proc_26977_broken;
+drop procedure proc_26977_works;
 End of 5.0 tests.