Details
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Type:
Bug
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Status: Closed
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Priority:
Minor
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Resolution: Fixed
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Affects Version/s: 5.5.37, 10.0.11, 10.1.0
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Fix Version/s: 10.1.1
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Component/s: None
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Labels:None
Description
Leaving variables uninitialized in certain cases helps to achieve top-notch performance. Sometimes compiler thinks that variable may be used uninitialized (whereas it may not) and emits a warning.
To silence these warnings there is UNINIT_VAR() macro:
#if defined(_lint) || defined(FORCE_INIT_OF_VARS) || \
defined(__cplusplus) || !defined(__GNUC__)
#define UNINIT_VAR(x) x= 0
#else
/* GCC specific self-initialization which inhibits the warning. */
#define UNINIT_VAR(x) x= x
#endif
There are a few problems with this macro:
1. It always emits "x= 0" for non-gcc
2. It always emits "x= 0" for C++ code
It means leaving variable uninitialized makes sense only in C code compiled by gcc.
Regarding __cplusplus: there is a reference to gcc bug which was fixed 3 years ago. Probably it is time to remove it?
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Ok to push.
let's handle LINT_INIT/etc warnings separately
Fixed in 10.1.1:
commit bb11eb82d5dce664e151519577df173acb31ee91
Author: Sergey Vojtovich <svoj@mariadb.org>
Date: Tue Aug 26 14:57:09 2014 +0400
MDEV-6305 - UNINIT_VAR emits code in non-debug builds
Reverted workaround for gcc bug, which was fixed 3 years ago:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34772
Sergei, please review fix for this bug.
Though I doubt it is a good idea to "Always enable -Wall for gnu C/C++" bypassing cmake maintainer mode (specifically FORCE_INIT_OF_VARS).
Now we get more warnings from LINT_INIT(). And there is also LINT_INIT_STRUCT() which didn't work before.