Re: [alsa-devel] [PATCH 01/06] Fix compilation warning for sound/soc/codecs/wm8400.c
On Thu, Jul 16, 2009 at 06:40:01PM +0530, Subrata Modak wrote:
How about the following brutal shutdown ?
No, this is the patch you originally submitted. You are missing the point here - your patches are all just papering over the warning and won't help at all if there is an actual problem.
'factors' will get initialized here, as, 'freq_out' will probably never have a '0' value. So, 'fll_factors()' will actually overwrite values in 'factors' even after the initial brutal assignment: "struct fll_factors factors = {}"
This is pretty much the point of the warning when it's valid - it's trying to catch situations where there is a code path where the variable is used without being initialised. If you just blindly initialise the variable as you are doing then the warning goes away but any problematic code remains so the situation is worse.
In this case I suspect that whatever compiler you are using (none of those I've tried with seem to be doing this) isn't able to figure out that if we skip initialising the variable then we use exactly the same condition to return from the function before we try to use the variable. For something like this the warning can normally be worked around by changing the control flow so that the compiler is able to figure out that things are safe.
At Thu, 16 Jul 2009 14:23:08 +0100, Mark Brown wrote:
On Thu, Jul 16, 2009 at 06:40:01PM +0530, Subrata Modak wrote:
How about the following brutal shutdown ?
No, this is the patch you originally submitted. You are missing the point here - your patches are all just papering over the warning and won't help at all if there is an actual problem.
'factors' will get initialized here, as, 'freq_out' will probably never have a '0' value. So, 'fll_factors()' will actually overwrite values in 'factors' even after the initial brutal assignment: "struct fll_factors factors = {}"
This is pretty much the point of the warning when it's valid - it's trying to catch situations where there is a code path where the variable is used without being initialised. If you just blindly initialise the variable as you are doing then the warning goes away but any problematic code remains so the situation is worse.
In this case I suspect that whatever compiler you are using (none of those I've tried with seem to be doing this) isn't able to figure out that if we skip initialising the variable then we use exactly the same condition to return from the function before we try to use the variable.
I get compile warnings on gcc 4.4.0, too.
For something like this the warning can normally be worked around by changing the control flow so that the compiler is able to figure out that things are safe.
Agreed.
Takashi
On Thu, Jul 16, 2009 at 03:34:06PM +0200, Takashi Iwai wrote:
Mark Brown wrote:
In this case I suspect that whatever compiler you are using (none of those I've tried with seem to be doing this) isn't able to figure out that if we skip initialising the variable then we use exactly the same condition to return from the function before we try to use the variable.
I get compile warnings on gcc 4.4.0, too.
Ah, that's useful - my GCC 4.4 system is at home so I can't try that one immediately. Which architecture?
At Thu, 16 Jul 2009 14:47:01 +0100, Mark Brown wrote:
On Thu, Jul 16, 2009 at 03:34:06PM +0200, Takashi Iwai wrote:
Mark Brown wrote:
In this case I suspect that whatever compiler you are using (none of those I've tried with seem to be doing this) isn't able to figure out that if we skip initialising the variable then we use exactly the same condition to return from the function before we try to use the variable.
I get compile warnings on gcc 4.4.0, too.
Ah, that's useful - my GCC 4.4 system is at home so I can't try that one immediately. Which architecture?
x86_64, at least.
Takashi
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Mark Brown -
Takashi Iwai