Re: [PATCH][version 3]add -ftrivial-auto-var-init and variable attribute "uninitialized" to gcc

[Qing Zhao <qing.zhao@oracle.com>]

So, the major question now is:

Is one single repeatable pattern enough for pattern initialization for all different types of auto variables?

If YES, then the implementation for pattern initialization will be much easier and simpler
      as you pointed out. And will save me a lot of pain to implement this part.
If NO, then we have to keep the current complicate implementation since it provides us
      the flexibility to assign different patterns to different types.

Honestly, I don’t have a good justification on this question myself.

The previous references I have so far are the current behavior of CLANG and Microsoft compiler.

For your reference,
. CLANG uses different patterns for INTEGER  (0xAAAAAAAA) and FLOAT (0xFFFFFFFF) and 32-bit pointer (0x000000AA)
https://reviews.llvm.org/D54604
. Microsoft uses different patterns for INTEGERS ( 0xE2), FLOAT (1.0)
https://msrc-blog.microsoft.com/2020/05/13/solving-uninitialized-stack-memory-on-windows/

My understanding from CLANG’s comment is, the patterns are easier to crash the program for the certain type, therefore easier to
catch any potential bugs.
Don’t know why Microsoft chose the pattern like this.

So, For GCC, what should we do on the pattern initializations, shall we choose one single repeatable pattern for all the types as you suggested,
Or chose different patterns for different types as Clang and Microsoft compiler’s behavior?

Kees, do you have any comment on this?

How did Linux Kernel use -ftrivial-auto-var-init=pattern feature of CLANG?

Thanks.

Qing