Re: [fpc-devel] "unused variable" depends on optimization?

[Florian Klämpfl via fpc-devel]

> Am 23.02.2025 um 14:26 schrieb Martin Frb via fpc-devel 
> <fpc-devel@lists.freepascal.org>:
> 
> On 23/02/2025 14:16, Jonas Maebe via fpc-devel wrote:
>> On 23/02/2025 14:14, Martin Frb via fpc-devel wrote:
>>> Is it correct (i.e. by design) that the compiler emits some "may not be 
>>> initialized" warnings, only on certain optimization levels?
>> 
>> Yes. Those warnings depends on data flow analysis, which is only enabled by 
>> defaullt at -O3 and higher. You can also enabled it separately with -Oodfa.
> 
> Ok, so without dfa it does not omit the warning, probably because it has see 
> that there was a conditional initialization? (i.e. might be ok, at least 
> sometimes, even if certainly not always)
> 
> Meaning -O1 is lenient in its checks, because they are not as evolved.

Yes, with -O1 the compiler does not see that the variable is initialized only 
conditionally. With -Oodfa/-O3 it takes care of this but actually it should 
also know about the condition being the same, something it cannot do at any 
optimization level.
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