[MDEV-14419] clang x86_64 test failure - main.select - converting strings of numbers to compare against large bigint - loss of precision Created: 2017-11-16  Updated: 2018-06-29

Status: Open
Project: MariaDB Server
Component/s: Data types
Affects Version/s: 10.2
Fix Version/s: 10.2

Type: Bug Priority: Major
Reporter: Daniel Black Assignee: Vicențiu Ciorbaru
Resolution: Unresolved Votes: 1
Labels: clang
Environment:

clang 3.9, 4.0, 5.0


 Description   

As discovered on travis, clang test (simplified as below fail).

Simplified test

create table  t1 (  A_Id bigint(20) NOT NULL default '0',  A_UpdateBy char(10) NOT NULL default '',  A_UpdateDate bigint(20) NOT NULL default '0',  A_UpdateSerial int(11) NOT NULL default '0',  other_types bigint(20) NOT NULL default '0',  wss_type bigint(20) NOT NULL default '0');
 
INSERT INTO t1 VALUES (102935998719055004,'brade',1029359987,2,102935229116544068,102935229216544093);
 
select wss_type from t1 where wss_type ='102935229216544093';

This returns no results.

As discovered with cvicentiu, the error manifests in stored_field_cmp_to_item.

item_cmp_type returns a common factor of REAL between string and INT types and therefore adopts a double based equality test at the end of the stored_field_cmp_to_item function.

Unfortunately the results for the conversion from the ulonglong in item->val_real() and field->val_real() differ by ~80 resulting in no equally and the SQL statement returning the wrong result.

Options include:
a) pushing an error when users quote numbers in queries - probably too common
b) fix this such that where this string is meticulously parsed in my_strntoull10rnd_8bit, b1) the ability to convert this to an integer is determined. Special cases? exponents detected (these are tested that it still falls < CUTOFF so no action taken b2) large -ve exponents are rounded to 0. b3) Decimals are rounded (handle to DECIMAL type).
c) fudge the test case until it pops up again

 Comments   
Comment by Daniel Black [ 2017-12-01 ]

On 10.2 branch at f59a1826f81e3246735c2ca61daec794170b61d1

fails:

$ clang --version
clang version 4.0.1 (tags/RELEASE_401/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

(from: clang-4.0.1-5.fc26.src.rpm)

fails:

clang version 5.0.0 (git://gitlab.ozlabs.ibm.com/mirror/llvm-clang.git 79a6eca386d468058b31e2d4f54b1b736a12f558) (git://gitlab.ozlabs.ibm.com/mirror/llvm.git 31f450353208e4d108fff264a2eba433758a0709)

circa march 2017 (https://github.com/llvm-mirror/clang/commit/79a6eca386d468058b31e2d4f54b1b736a12f558). Git commits correspond to upstream git mirror.

(cd mysql-test/; ./mtr test)
 
clang version 5.0.0 (git://gitlab.ozlabs.ibm.com/mirror/llvm-clang.git 79a6eca386d468058b31e2d4f54b1b736a12f558) (git://gitlab.ozlabs.ibm.com/mirror/llvm.git 31f450353208e4d108fff264a2eba433758a0709)
 
Target: x86_64-unknown-linux-gnu
 
Thread model: posix
 
InstalledDir: /home/dan/clang/bin
 
Logging: /home/dan/repos/mariadb-server/mysql-test/mysql-test-run.pl  test
 
vardir: /home/dan/repos/build-mariadb-10.2-clang-5.0/mysql-test/var
 
Checking leftover processes...
 
Removing old var directory...
 
Creating var directory '/home/dan/repos/build-mariadb-10.2-clang-5.0/mysql-test/var'...
 
Checking supported features...
 
MariaDB Version 10.2.12-MariaDB
 
 - SSL connections supported
 
Collecting tests...
 
Installing system database...
 
 
 
==============================================================================
 
 
 
TEST                                      RESULT   TIME (ms) or COMMENT
 
--------------------------------------------------------------------------
 
 
 
worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 16000..16019
 
create table  t1 (  A_Id bigint(20) NOT NULL default '0',  A_UpdateBy char(10) NOT NULL default '',  A_UpdateDate bigint(20) NOT NULL default '0',  A_UpdateSerial int(11) NOT NULL default '0',  other_types bigint(20) NOT NULL default '0',  wss_type bigint(20) NOT NULL default '0');
 
INSERT INTO t1 VALUES (102935998719055004,'brade',1029359987,2,102935229116544068,102935229216544093);
 
select wss_type from t1 where wss_type ='102935229216544093';
 
wss_type
 
SHOW WARNINGS;
 
Level   Code    Message
 
select wss_type from t1 where wss_type =0x16DB30BAC53555D;
 
wss_type
 
102935229216544093
 
SHOW WARNINGS;
 
Level   Code    Message
 
select wss_type from t1 where wss_type =102935229216544093;
 
wss_type
 
102935229216544093

works: clang-6.0 from November 2017

$ /home/dan/clang-6.0/bin/clang++ --version  && (cd mysql-test/; ./mtr select)
 
/home/dan/clang-6.0/bin/clang++: /lib64/libtinfo.so.5: no version information available (required by /home/dan/clang-6.0/bin/clang++)
 
clang version 6.0.0 (git://gitlab.ozlabs.ibm.com/mirror/llvm-clang.git 24008b27d5f4c12c43f88e6f4037f16ec43a8bc3) (git://gitlab.ozlabs.ibm.com/mirror/llvm.git 0d7d3a3c3255f9bafe37485d33262aa10ef8f29f)
 
Target: x86_64-unknown-linux-gnu
 
Thread model: posix
 
InstalledDir: /home/dan/clang-6.0/bin
 
Logging: /home/dan/repos/mariadb-server/mysql-test/mysql-test-run.pl  select
 
vardir: /home/dan/repos/build-mariadb-10.2-clang-6.0/mysql-test/var
 
Checking leftover processes...
 
Removing old var directory...
 
Creating var directory '/home/dan/repos/build-mariadb-10.2-clang-6.0/mysql-test/var'...
 
Checking supported features...
 
MariaDB Version 10.2.12-MariaDB
 
 - SSL connections supported
 
Collecting tests...
 
Installing system database...
 
 
 
==============================================================================
 
 
 
TEST                                      RESULT   TIME (ms) or COMMENT
 
--------------------------------------------------------------------------
 
 
 
worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 16000..16019
 
main.select                              [ pass ]   1708
 
--------------------------------------------------------------------------
 
The servers were restarted 0 times
 
Spent 1.708 of 5 seconds executing testcases
 
 
 
Completed: All 1 tests were successful.

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